[apple/xnu.git] / bsd / kern / decmpfs.c

/*
 * Copyright (c) 2008-2018 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
#if !FS_COMPRESSION

/* We need these symbols even though compression is turned off */

#define UNUSED_SYMBOL(x)        asm(".global _" #x "\n.set _" #x ", 0\n");

UNUSED_SYMBOL(register_decmpfs_decompressor)
UNUSED_SYMBOL(unregister_decmpfs_decompressor)
UNUSED_SYMBOL(decmpfs_init)
UNUSED_SYMBOL(decmpfs_read_compressed)
UNUSED_SYMBOL(decmpfs_cnode_cmp_type)
UNUSED_SYMBOL(decmpfs_cnode_get_vnode_state)
UNUSED_SYMBOL(decmpfs_cnode_get_vnode_cached_size)
UNUSED_SYMBOL(decmpfs_lock_compressed_data)
UNUSED_SYMBOL(decmpfs_cnode_free)
UNUSED_SYMBOL(decmpfs_cnode_alloc)
UNUSED_SYMBOL(decmpfs_cnode_destroy)
UNUSED_SYMBOL(decmpfs_decompress_file)
UNUSED_SYMBOL(decmpfs_unlock_compressed_data)
UNUSED_SYMBOL(decmpfs_cnode_init)
UNUSED_SYMBOL(decmpfs_cnode_set_vnode_state)
UNUSED_SYMBOL(decmpfs_hides_xattr)
UNUSED_SYMBOL(decmpfs_ctx)
UNUSED_SYMBOL(decmpfs_file_is_compressed)
UNUSED_SYMBOL(decmpfs_update_attributes)
UNUSED_SYMBOL(decmpfs_hides_rsrc)
UNUSED_SYMBOL(decmpfs_pagein_compressed)
UNUSED_SYMBOL(decmpfs_validate_compressed_file)

#else /* FS_COMPRESSION */
#include <sys/kernel.h>
#include <sys/vnode_internal.h>
#include <sys/file_internal.h>
#include <sys/stat.h>
#include <sys/fcntl.h>
#include <sys/xattr.h>
#include <sys/namei.h>
#include <sys/user.h>
#include <sys/mount_internal.h>
#include <sys/ubc.h>
#include <sys/decmpfs.h>
#include <sys/uio_internal.h>
#include <libkern/OSByteOrder.h>
#include <libkern/section_keywords.h>

#pragma mark --- debugging ---

#define COMPRESSION_DEBUG 0
#define COMPRESSION_DEBUG_VERBOSE 0
#define MALLOC_DEBUG 0

static const char *
baseName(const char *path)
{
        if (!path) {
                return NULL;
        }
        const char *ret = path;
        int i;
        for (i = 0; path[i] != 0; i++) {
                if (path[i] == '/') {
                        ret = &path[i + 1];
                }
        }
        return ret;
}

static char*
vnpath(vnode_t vp, char *path, int len)
{
        int origlen = len;
        path[0] = 0;
        vn_getpath(vp, path, &len);
        path[origlen - 1] = 0;
        return path;
}

#define ErrorLog(x, args...) printf("%s:%d:%s: " x, baseName(__FILE__), __LINE__, __FUNCTION__, ## args)
#define ErrorLogWithPath(x, args...) do { char *path; MALLOC(path, char *, PATH_MAX, M_TEMP, M_WAITOK); printf("%s:%d:%s: %s: " x, baseName(__FILE__), __LINE__, __FUNCTION__, vnpath(vp, path, PATH_MAX), ## args); FREE(path, M_TEMP); } while(0)

#if COMPRESSION_DEBUG
#define DebugLog ErrorLog
#define DebugLogWithPath ErrorLogWithPath
#else
#define DebugLog(x...) do { } while(0)
#define DebugLogWithPath(x...) do { } while(0)
#endif

#if COMPRESSION_DEBUG_VERBOSE
#define VerboseLog ErrorLog
#define VerboseLogWithPath ErrorLogWithPath
#else
#define VerboseLog(x...) do { } while(0)
#define VerboseLogWithPath(x...) do { } while(0)
#endif

#if MALLOC_DEBUG

static SInt32 totalAlloc;

typedef struct {
        uint32_t allocSz;
        uint32_t magic;
        const char *file;
        int line;
} allocated;

static void *
_malloc(uint32_t sz, __unused int type, __unused int flags, const char *file, int line)
{
        uint32_t allocSz = sz + 2 * sizeof(allocated);

        allocated *alloc = NULL;
        MALLOC(alloc, allocated *, allocSz, type, flags);
        if (!alloc) {
                ErrorLog("malloc failed\n");
                return NULL;
        }

        char *ret = (char*)&alloc[1];
        allocated *alloc2 = (allocated*)(ret + sz);

        alloc->allocSz = allocSz;
        alloc->magic = 0xdadadada;
        alloc->file = file;
        alloc->line = line;

        *alloc2 = *alloc;

        int s = OSAddAtomic(sz, &totalAlloc);
        ErrorLog("malloc(%d) -> %p, total allocations %d\n", sz, ret, s + sz);

        return ret;
}

static void
_free(char *ret, __unused int type, const char *file, int line)
{
        if (!ret) {
                ErrorLog("freeing null\n");
                return;
        }
        allocated *alloc = (allocated*)ret;
        alloc--;
        uint32_t sz = alloc->allocSz - 2 * sizeof(allocated);
        allocated *alloc2 = (allocated*)(ret + sz);

        if (alloc->magic != 0xdadadada) {
                panic("freeing bad pointer");
        }

        if (memcmp(alloc, alloc2, sizeof(*alloc)) != 0) {
                panic("clobbered data");
        }

        memset(ret, 0xce, sz);
        alloc2->file = file;
        alloc2->line = line;
        FREE(alloc, type);
        int s = OSAddAtomic(-sz, &totalAlloc);
        ErrorLog("free(%p,%d) -> total allocations %d\n", ret, sz, s - sz);
}

#undef MALLOC
#undef FREE
#define MALLOC(space, cast, size, type, flags) (space) = (cast)_malloc(size, type, flags, __FILE__, __LINE__)
#define FREE(addr, type) _free((void *)addr, type, __FILE__, __LINE__)

#endif /* MALLOC_DEBUG */

#pragma mark --- globals ---

static lck_grp_t *decmpfs_lockgrp;

SECURITY_READ_ONLY_EARLY(static decmpfs_registration *) decompressors[CMP_MAX]; /* the registered compressors */
static lck_rw_t * decompressorsLock;
static int decompress_channel; /* channel used by decompress_file to wake up waiters */
static lck_mtx_t *decompress_channel_mtx;

vfs_context_t decmpfs_ctx;

#pragma mark --- decmp_get_func ---

#define offsetof_func(func) ((uintptr_t)(&(((decmpfs_registration*)NULL)->func)))

static void *
_func_from_offset(uint32_t type, uintptr_t offset)
{
        /* get the function at the given offset in the registration for the given type */
        const decmpfs_registration *reg = decompressors[type];
        const char *regChar = (const char*)reg;
        const char *func = &regChar[offset];
        void * const * funcPtr = (void * const *) func;

        switch (reg->decmpfs_registration) {
        case DECMPFS_REGISTRATION_VERSION_V1:
                if (offset > offsetof_func(free_data)) {
                        return NULL;
                }
                break;
        case DECMPFS_REGISTRATION_VERSION_V3:
                if (offset > offsetof_func(get_flags)) {
                        return NULL;
                }
                break;
        default:
                return NULL;
        }

        return funcPtr[0];
}

extern void IOServicePublishResource( const char * property, boolean_t value );
extern boolean_t IOServiceWaitForMatchingResource( const char * property, uint64_t timeout );
extern boolean_t IOCatalogueMatchingDriversPresent( const char * property );

static void *
_decmp_get_func(vnode_t vp, uint32_t type, uintptr_t offset)
{
        /*
         *  this function should be called while holding a shared lock to decompressorsLock,
         *  and will return with the lock held
         */

        if (type >= CMP_MAX) {
                return NULL;
        }

        if (decompressors[type] != NULL) {
                // the compressor has already registered but the function might be null
                return _func_from_offset(type, offset);
        }

        // does IOKit know about a kext that is supposed to provide this type?
        char providesName[80];
        snprintf(providesName, sizeof(providesName), "com.apple.AppleFSCompression.providesType%u", type);
        if (IOCatalogueMatchingDriversPresent(providesName)) {
                // there is a kext that says it will register for this type, so let's wait for it
                char resourceName[80];
                uint64_t delay = 10000000ULL; // 10 milliseconds.
                snprintf(resourceName, sizeof(resourceName), "com.apple.AppleFSCompression.Type%u", type);
                ErrorLogWithPath("waiting for %s\n", resourceName);
                while (decompressors[type] == NULL) {
                        lck_rw_unlock_shared(decompressorsLock); // we have to unlock to allow the kext to register
                        if (IOServiceWaitForMatchingResource(resourceName, delay)) {
                                lck_rw_lock_shared(decompressorsLock);
                                break;
                        }
                        if (!IOCatalogueMatchingDriversPresent(providesName)) {
                                //
                                ErrorLogWithPath("the kext with %s is no longer present\n", providesName);
                                lck_rw_lock_shared(decompressorsLock);
                                break;
                        }
                        ErrorLogWithPath("still waiting for %s\n", resourceName);
                        delay *= 2;
                        lck_rw_lock_shared(decompressorsLock);
                }
                // IOKit says the kext is loaded, so it should be registered too!
                if (decompressors[type] == NULL) {
                        ErrorLogWithPath("we found %s, but the type still isn't registered\n", providesName);
                        return NULL;
                }
                // it's now registered, so let's return the function
                return _func_from_offset(type, offset);
        }

        // the compressor hasn't registered, so it never will unless someone manually kextloads it
        ErrorLogWithPath("tried to access a compressed file of unregistered type %d\n", type);
        return NULL;
}

#define decmp_get_func(vp, type, func) ((typeof(((decmpfs_registration*)NULL)->func))_decmp_get_func(vp, type, offsetof_func(func)))

#pragma mark --- utilities ---

#if COMPRESSION_DEBUG
static int
vnsize(vnode_t vp, uint64_t *size)
{
        struct vnode_attr va;
        VATTR_INIT(&va);
        VATTR_WANTED(&va, va_data_size);
        int error = vnode_getattr(vp, &va, decmpfs_ctx);
        if (error != 0) {
                ErrorLogWithPath("vnode_getattr err %d\n", error);
                return error;
        }
        *size = va.va_data_size;
        return 0;
}
#endif /* COMPRESSION_DEBUG */

#pragma mark --- cnode routines ---

decmpfs_cnode *
decmpfs_cnode_alloc(void)
{
        decmpfs_cnode *dp;
        MALLOC_ZONE(dp, decmpfs_cnode *, sizeof(decmpfs_cnode), M_DECMPFS_CNODE, M_WAITOK);
        return dp;
}

void
decmpfs_cnode_free(decmpfs_cnode *dp)
{
        FREE_ZONE(dp, sizeof(*dp), M_DECMPFS_CNODE);
}

void
decmpfs_cnode_init(decmpfs_cnode *cp)
{
        memset(cp, 0, sizeof(*cp));
        lck_rw_init(&cp->compressed_data_lock, decmpfs_lockgrp, NULL);
}

void
decmpfs_cnode_destroy(decmpfs_cnode *cp)
{
        lck_rw_destroy(&cp->compressed_data_lock, decmpfs_lockgrp);
}

bool
decmpfs_trylock_compressed_data(decmpfs_cnode *cp, int exclusive)
{
        void *thread = current_thread();
        bool retval = false;

        if (cp->lockowner == thread) {
                /* this thread is already holding an exclusive lock, so bump the count */
                cp->lockcount++;
                retval = true;
        } else if (exclusive) {
                if ((retval = lck_rw_try_lock_exclusive(&cp->compressed_data_lock))) {
                        cp->lockowner = thread;
                        cp->lockcount = 1;
                }
        } else {
                if ((retval = lck_rw_try_lock_shared(&cp->compressed_data_lock))) {
                        cp->lockowner = (void *)-1;
                }
        }
        return retval;
}

void
decmpfs_lock_compressed_data(decmpfs_cnode *cp, int exclusive)
{
        void *thread = current_thread();

        if (cp->lockowner == thread) {
                /* this thread is already holding an exclusive lock, so bump the count */
                cp->lockcount++;
        } else if (exclusive) {
                lck_rw_lock_exclusive(&cp->compressed_data_lock);
                cp->lockowner = thread;
                cp->lockcount = 1;
        } else {
                lck_rw_lock_shared(&cp->compressed_data_lock);
                cp->lockowner = (void *)-1;
        }
}

void
decmpfs_unlock_compressed_data(decmpfs_cnode *cp, __unused int exclusive)
{
        void *thread = current_thread();

        if (cp->lockowner == thread) {
                /* this thread is holding an exclusive lock, so decrement the count */
                if ((--cp->lockcount) > 0) {
                        /* the caller still has outstanding locks, so we're done */
                        return;
                }
                cp->lockowner = NULL;
        }

        lck_rw_done(&cp->compressed_data_lock);
}

uint32_t
decmpfs_cnode_get_vnode_state(decmpfs_cnode *cp)
{
        return cp->cmp_state;
}

void
decmpfs_cnode_set_vnode_state(decmpfs_cnode *cp, uint32_t state, int skiplock)
{
        if (!skiplock) {
                decmpfs_lock_compressed_data(cp, 1);
        }
        cp->cmp_state = state;
        if (state == FILE_TYPE_UNKNOWN) {
                /* clear out the compression type too */
                cp->cmp_type = 0;
        }
        if (!skiplock) {
                decmpfs_unlock_compressed_data(cp, 1);
        }
}

static void
decmpfs_cnode_set_vnode_cmp_type(decmpfs_cnode *cp, uint32_t cmp_type, int skiplock)
{
        if (!skiplock) {
                decmpfs_lock_compressed_data(cp, 1);
        }
        cp->cmp_type = cmp_type;
        if (!skiplock) {
                decmpfs_unlock_compressed_data(cp, 1);
        }
}

static void
decmpfs_cnode_set_vnode_minimal_xattr(decmpfs_cnode *cp, int minimal_xattr, int skiplock)
{
        if (!skiplock) {
                decmpfs_lock_compressed_data(cp, 1);
        }
        cp->cmp_minimal_xattr = minimal_xattr;
        if (!skiplock) {
                decmpfs_unlock_compressed_data(cp, 1);
        }
}

uint64_t
decmpfs_cnode_get_vnode_cached_size(decmpfs_cnode *cp)
{
        return cp->uncompressed_size;
}

static void
decmpfs_cnode_set_vnode_cached_size(decmpfs_cnode *cp, uint64_t size)
{
        while (1) {
                uint64_t old = cp->uncompressed_size;
                if (OSCompareAndSwap64(old, size, (UInt64*)&cp->uncompressed_size)) {
                        return;
                } else {
                        /* failed to write our value, so loop */
                }
        }
}

static uint64_t
decmpfs_cnode_get_decompression_flags(decmpfs_cnode *cp)
{
        return cp->decompression_flags;
}

static void
decmpfs_cnode_set_decompression_flags(decmpfs_cnode *cp, uint64_t flags)
{
        while (1) {
                uint64_t old = cp->decompression_flags;
                if (OSCompareAndSwap64(old, flags, (UInt64*)&cp->decompression_flags)) {
                        return;
                } else {
                        /* failed to write our value, so loop */
                }
        }
}

uint32_t
decmpfs_cnode_cmp_type(decmpfs_cnode *cp)
{
        return cp->cmp_type;
}

#pragma mark --- decmpfs state routines ---

static int
decmpfs_fetch_compressed_header(vnode_t vp, decmpfs_cnode *cp, decmpfs_header **hdrOut, int returnInvalid)
{
        /*
         *  fetches vp's compression xattr, converting it into a decmpfs_header; returns 0 or errno
         *  if returnInvalid == 1, returns the header even if the type was invalid (out of range),
         *  and return ERANGE in that case
         */

        size_t read_size             = 0;
        size_t attr_size             = 0;
        uio_t attr_uio               = NULL;
        int err                      = 0;
        char *data                   = NULL;
        const bool no_additional_data = ((cp != NULL)
            && (cp->cmp_type != 0)
            && (cp->cmp_minimal_xattr != 0));
        char uio_buf[UIO_SIZEOF(1)];
        decmpfs_header *hdr = NULL;

        /*
         * Trace the following parameters on entry with event-id 0x03120004
         *
         * @vp->v_id:       vnode-id for which to fetch compressed header.
         * @no_additional_data: If set true then xattr didn't have any extra data.
         * @returnInvalid:  return the header even though the type is out of range.
         */
        DECMPFS_EMIT_TRACE_ENTRY(DECMPDBG_FETCH_COMPRESSED_HEADER, vp->v_id,
            no_additional_data, returnInvalid);

        if (no_additional_data) {
                /* this file's xattr didn't have any extra data when we fetched it, so we can synthesize a header from the data in the cnode */

                MALLOC(data, char *, sizeof(decmpfs_header), M_TEMP, M_WAITOK);
                if (!data) {
                        err = ENOMEM;
                        goto out;
                }
                hdr = (decmpfs_header*)data;
                hdr->attr_size = sizeof(decmpfs_disk_header);
                hdr->compression_magic = DECMPFS_MAGIC;
                hdr->compression_type  = cp->cmp_type;
                hdr->uncompressed_size = decmpfs_cnode_get_vnode_cached_size(cp);
        } else {
                /* figure out how big the xattr is on disk */
                err = vn_getxattr(vp, DECMPFS_XATTR_NAME, NULL, &attr_size, XATTR_NOSECURITY, decmpfs_ctx);
                if (err != 0) {
                        goto out;
                }

                if (attr_size < sizeof(decmpfs_disk_header) || attr_size > MAX_DECMPFS_XATTR_SIZE) {
                        err = EINVAL;
                        goto out;
                }

                /* allocation includes space for the extra attr_size field of a compressed_header */
                MALLOC(data, char *, attr_size + sizeof(hdr->attr_size), M_TEMP, M_WAITOK);
                if (!data) {
                        err = ENOMEM;
                        goto out;
                }

                /* read the xattr into our buffer, skipping over the attr_size field at the beginning */
                attr_uio = uio_createwithbuffer(1, 0, UIO_SYSSPACE, UIO_READ, &uio_buf[0], sizeof(uio_buf));
                uio_addiov(attr_uio, CAST_USER_ADDR_T(data + sizeof(hdr->attr_size)), attr_size);

                err = vn_getxattr(vp, DECMPFS_XATTR_NAME, attr_uio, &read_size, XATTR_NOSECURITY, decmpfs_ctx);
                if (err != 0) {
                        goto out;
                }
                if (read_size != attr_size) {
                        err = EINVAL;
                        goto out;
                }
                hdr = (decmpfs_header*)data;
                hdr->attr_size = attr_size;
                /* swap the fields to native endian */
                hdr->compression_magic = OSSwapLittleToHostInt32(hdr->compression_magic);
                hdr->compression_type  = OSSwapLittleToHostInt32(hdr->compression_type);
                hdr->uncompressed_size = OSSwapLittleToHostInt64(hdr->uncompressed_size);
        }

        if (hdr->compression_magic != DECMPFS_MAGIC) {
                ErrorLogWithPath("invalid compression_magic 0x%08x, should be 0x%08x\n", hdr->compression_magic, DECMPFS_MAGIC);
                err = EINVAL;
                goto out;
        }

        if (hdr->compression_type >= CMP_MAX) {
                if (returnInvalid) {
                        /* return the header even though the type is out of range */
                        err = ERANGE;
                } else {
                        ErrorLogWithPath("compression_type %d out of range\n", hdr->compression_type);
                        err = EINVAL;
                }
                goto out;
        }

out:
        if (err && (err != ERANGE)) {
                DebugLogWithPath("err %d\n", err);
                if (data) {
                        FREE(data, M_TEMP);
                }
                *hdrOut = NULL;
        } else {
                *hdrOut = hdr;
        }
        /*
         * Trace the following parameters on return with event-id 0x03120004.
         *
         * @vp->v_id:       vnode-id for which to fetch compressed header.
         * @err:            value returned from this function.
         */
        DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FETCH_COMPRESSED_HEADER, vp->v_id, err);
        return err;
}

static int
decmpfs_fast_get_state(decmpfs_cnode *cp)
{
        /*
         *  return the cached state
         *  this should *only* be called when we know that decmpfs_file_is_compressed has already been called,
         *  because this implies that the cached state is valid
         */
        int cmp_state = decmpfs_cnode_get_vnode_state(cp);

        switch (cmp_state) {
        case FILE_IS_NOT_COMPRESSED:
        case FILE_IS_COMPRESSED:
        case FILE_IS_CONVERTING:
                return cmp_state;
        case FILE_TYPE_UNKNOWN:
                /*
                 *  we should only get here if decmpfs_file_is_compressed was not called earlier on this vnode,
                 *  which should not be possible
                 */
                ErrorLog("decmpfs_fast_get_state called on unknown file\n");
                return FILE_IS_NOT_COMPRESSED;
        default:
                /* */
                ErrorLog("unknown cmp_state %d\n", cmp_state);
                return FILE_IS_NOT_COMPRESSED;
        }
}

static int
decmpfs_fast_file_is_compressed(decmpfs_cnode *cp)
{
        int cmp_state = decmpfs_cnode_get_vnode_state(cp);

        switch (cmp_state) {
        case FILE_IS_NOT_COMPRESSED:
                return 0;
        case FILE_IS_COMPRESSED:
        case FILE_IS_CONVERTING:
                return 1;
        case FILE_TYPE_UNKNOWN:
                /*
                 *  we should only get here if decmpfs_file_is_compressed was not called earlier on this vnode,
                 *  which should not be possible
                 */
                ErrorLog("decmpfs_fast_get_state called on unknown file\n");
                return 0;
        default:
                /* */
                ErrorLog("unknown cmp_state %d\n", cmp_state);
                return 0;
        }
}

errno_t
decmpfs_validate_compressed_file(vnode_t vp, decmpfs_cnode *cp)
{
        /* give a compressor a chance to indicate that a compressed file is invalid */

        decmpfs_header *hdr = NULL;
        errno_t err = decmpfs_fetch_compressed_header(vp, cp, &hdr, 0);
        if (err) {
                /* we couldn't get the header */
                if (decmpfs_fast_get_state(cp) == FILE_IS_NOT_COMPRESSED) {
                        /* the file is no longer compressed, so return success */
                        err = 0;
                }
                goto out;
        }

        lck_rw_lock_shared(decompressorsLock);
        decmpfs_validate_compressed_file_func validate = decmp_get_func(vp, hdr->compression_type, validate);
        if (validate) { /* make sure this validation function is valid */
                /* is the data okay? */
                err = validate(vp, decmpfs_ctx, hdr);
        } else if (decmp_get_func(vp, hdr->compression_type, fetch) == NULL) {
                /* the type isn't registered */
                err = EIO;
        } else {
                /* no validate registered, so nothing to do */
                err = 0;
        }
        lck_rw_unlock_shared(decompressorsLock);
out:
        if (hdr) {
                FREE(hdr, M_TEMP);
        }
#if COMPRESSION_DEBUG
        if (err) {
                DebugLogWithPath("decmpfs_validate_compressed_file ret %d, vp->v_flag %d\n", err, vp->v_flag);
        }
#endif
        return err;
}

int
decmpfs_file_is_compressed(vnode_t vp, decmpfs_cnode *cp)
{
        /*
         *  determines whether vp points to a compressed file
         *
         *  to speed up this operation, we cache the result in the cnode, and do as little as possible
         *  in the case where the cnode already has a valid cached state
         *
         */

        int ret = 0;
        int error = 0;
        uint32_t cmp_state;
        struct vnode_attr va_fetch;
        decmpfs_header *hdr = NULL;
        mount_t mp = NULL;
        int cnode_locked = 0;
        int saveInvalid = 0; // save the header data even though the type was out of range
        uint64_t decompression_flags = 0;
        bool is_mounted, is_local_fs;

        if (vnode_isnamedstream(vp)) {
                /*
                 *  named streams can't be compressed
                 *  since named streams of the same file share the same cnode,
                 *  we don't want to get/set the state in the cnode, just return 0
                 */
                return 0;
        }

        /* examine the cached a state in this cnode */
        cmp_state = decmpfs_cnode_get_vnode_state(cp);
        switch (cmp_state) {
        case FILE_IS_NOT_COMPRESSED:
                return 0;
        case FILE_IS_COMPRESSED:
                return 1;
        case FILE_IS_CONVERTING:
                /* treat the file as compressed, because this gives us a way to block future reads until decompression is done */
                return 1;
        case FILE_TYPE_UNKNOWN:
                /* the first time we encountered this vnode, so we need to check it out */
                break;
        default:
                /* unknown state, assume file is not compressed */
                ErrorLogWithPath("unknown cmp_state %d\n", cmp_state);
                return 0;
        }

        if (!vnode_isreg(vp)) {
                /* only regular files can be compressed */
                ret = FILE_IS_NOT_COMPRESSED;
                goto done;
        }

        is_mounted = false;
        is_local_fs = false;
        mp = vnode_mount(vp);
        if (mp) {
                is_mounted = true;
        }
        if (is_mounted) {
                is_local_fs = ((mp->mnt_flag & MNT_LOCAL));
        }
        /*
         * Trace the following parameters on entry with event-id 0x03120014.
         *
         * @vp->v_id:       vnode-id of the file being queried.
         * @is_mounted:     set to true if @vp belongs to a mounted fs.
         * @is_local_fs:    set to true if @vp belongs to local fs.
         */
        DECMPFS_EMIT_TRACE_ENTRY(DECMPDBG_FILE_IS_COMPRESSED, vp->v_id,
            is_mounted, is_local_fs);

        if (!is_mounted) {
                /*
                 *  this should only be true before we mount the root filesystem
                 *  we short-cut this return to avoid the call to getattr below, which
                 *  will fail before root is mounted
                 */
                ret = FILE_IS_NOT_COMPRESSED;
                goto done;
        }

        if (!is_local_fs) {
                /* compression only supported on local filesystems */
                ret = FILE_IS_NOT_COMPRESSED;
                goto done;
        }

        /* lock our cnode data so that another caller doesn't change the state under us */
        decmpfs_lock_compressed_data(cp, 1);
        cnode_locked = 1;

        VATTR_INIT(&va_fetch);
        VATTR_WANTED(&va_fetch, va_flags);
        error = vnode_getattr(vp, &va_fetch, decmpfs_ctx);
        if (error) {
                /* failed to get the bsd flags so the file is not compressed */
                ret = FILE_IS_NOT_COMPRESSED;
                goto done;
        }
        if (va_fetch.va_flags & UF_COMPRESSED) {
                /* UF_COMPRESSED is on, make sure the file has the DECMPFS_XATTR_NAME xattr */
                error = decmpfs_fetch_compressed_header(vp, cp, &hdr, 1);
                if ((hdr != NULL) && (error == ERANGE)) {
                        saveInvalid = 1;
                }
                if (error) {
                        /* failed to get the xattr so the file is not compressed */
                        ret = FILE_IS_NOT_COMPRESSED;
                        goto done;
                }
                /* we got the xattr, so the file is compressed */
                ret = FILE_IS_COMPRESSED;
                goto done;
        }
        /* UF_COMPRESSED isn't on, so the file isn't compressed */
        ret = FILE_IS_NOT_COMPRESSED;

done:
        if (((ret == FILE_IS_COMPRESSED) || saveInvalid) && hdr) {
                /*
                 *  cache the uncompressed size away in the cnode
                 */

                if (!cnode_locked) {
                        /*
                         *  we should never get here since the only place ret is set to FILE_IS_COMPRESSED
                         *  is after the call to decmpfs_lock_compressed_data above
                         */
                        decmpfs_lock_compressed_data(cp, 1);
                        cnode_locked = 1;
                }

                decmpfs_cnode_set_vnode_cached_size(cp, hdr->uncompressed_size);
                decmpfs_cnode_set_vnode_state(cp, ret, 1);
                decmpfs_cnode_set_vnode_cmp_type(cp, hdr->compression_type, 1);
                /* remember if the xattr's size was equal to the minimal xattr */
                if (hdr->attr_size == sizeof(decmpfs_disk_header)) {
                        decmpfs_cnode_set_vnode_minimal_xattr(cp, 1, 1);
                }
                if (ret == FILE_IS_COMPRESSED) {
                        /* update the ubc's size for this file */
                        ubc_setsize(vp, hdr->uncompressed_size);

                        /* update the decompression flags in the decmpfs cnode */
                        lck_rw_lock_shared(decompressorsLock);
                        decmpfs_get_decompression_flags_func get_flags = decmp_get_func(vp, hdr->compression_type, get_flags);
                        if (get_flags) {
                                decompression_flags = get_flags(vp, decmpfs_ctx, hdr);
                        }
                        lck_rw_unlock_shared(decompressorsLock);
                        decmpfs_cnode_set_decompression_flags(cp, decompression_flags);
                }
        } else {
                /* we might have already taken the lock above; if so, skip taking it again by passing cnode_locked as the skiplock parameter */
                decmpfs_cnode_set_vnode_state(cp, ret, cnode_locked);
        }

        if (cnode_locked) {
                decmpfs_unlock_compressed_data(cp, 1);
        }

        if (hdr) {
                FREE(hdr, M_TEMP);
        }
        /*
         * Trace the following parameters on return with event-id 0x03120014.
         *
         * @vp->v_id:       vnode-id of the file being queried.
         * @return:         set to 1 is file is compressed.
         */
        switch (ret) {
        case FILE_IS_NOT_COMPRESSED:
                DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FILE_IS_COMPRESSED, vp->v_id, 0);
                return 0;
        case FILE_IS_COMPRESSED:
        case FILE_IS_CONVERTING:
                DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FILE_IS_COMPRESSED, vp->v_id, 1);
                return 1;
        default:
                /* unknown state, assume file is not compressed */
                DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FILE_IS_COMPRESSED, vp->v_id, 0);
                ErrorLogWithPath("unknown ret %d\n", ret);
                return 0;
        }
}

int
decmpfs_update_attributes(vnode_t vp, struct vnode_attr *vap)
{
        int error = 0;

        if (VATTR_IS_ACTIVE(vap, va_flags)) {
                /* the BSD flags are being updated */
                if (vap->va_flags & UF_COMPRESSED) {
                        /* the compressed bit is being set, did it change? */
                        struct vnode_attr va_fetch;
                        int old_flags = 0;
                        VATTR_INIT(&va_fetch);
                        VATTR_WANTED(&va_fetch, va_flags);
                        error = vnode_getattr(vp, &va_fetch, decmpfs_ctx);
                        if (error) {
                                return error;
                        }

                        old_flags = va_fetch.va_flags;

                        if (!(old_flags & UF_COMPRESSED)) {
                                /*
                                 * Compression bit was turned on, make sure the file has the DECMPFS_XATTR_NAME attribute.
                                 * This precludes anyone from using the UF_COMPRESSED bit for anything else, and it enforces
                                 * an order of operation -- you must first do the setxattr and then the chflags.
                                 */

                                if (VATTR_IS_ACTIVE(vap, va_data_size)) {
                                        /*
                                         * don't allow the caller to set the BSD flag and the size in the same call
                                         * since this doesn't really make sense
                                         */
                                        vap->va_flags &= ~UF_COMPRESSED;
                                        return 0;
                                }

                                decmpfs_header *hdr = NULL;
                                error = decmpfs_fetch_compressed_header(vp, NULL, &hdr, 1);
                                if (error == 0) {
                                        /*
                                         *  allow the flag to be set since the decmpfs attribute is present
                                         *  in that case, we also want to truncate the data fork of the file
                                         */
                                        VATTR_SET_ACTIVE(vap, va_data_size);
                                        vap->va_data_size = 0;
                                } else if (error == ERANGE) {
                                        /* the file had a decmpfs attribute but the type was out of range, so don't muck with the file's data size */
                                } else {
                                        /* no DECMPFS_XATTR_NAME attribute, so deny the update */
                                        vap->va_flags &= ~UF_COMPRESSED;
                                }
                                if (hdr) {
                                        FREE(hdr, M_TEMP);
                                }
                        }
                }
        }

        return 0;
}

static int
wait_for_decompress(decmpfs_cnode *cp)
{
        int state;
        lck_mtx_lock(decompress_channel_mtx);
        do {
                state = decmpfs_fast_get_state(cp);
                if (state != FILE_IS_CONVERTING) {
                        /* file is not decompressing */
                        lck_mtx_unlock(decompress_channel_mtx);
                        return state;
                }
                msleep((caddr_t)&decompress_channel, decompress_channel_mtx, PINOD, "wait_for_decompress", NULL);
        } while (1);
}

#pragma mark --- decmpfs hide query routines ---

int
decmpfs_hides_rsrc(vfs_context_t ctx, decmpfs_cnode *cp)
{
        /*
         *  WARNING!!!
         *  callers may (and do) pass NULL for ctx, so we should only use it
         *  for this equality comparison
         *
         *  This routine should only be called after a file has already been through decmpfs_file_is_compressed
         */

        if (ctx == decmpfs_ctx) {
                return 0;
        }

        if (!decmpfs_fast_file_is_compressed(cp)) {
                return 0;
        }

        /* all compressed files hide their resource fork */
        return 1;
}

int
decmpfs_hides_xattr(vfs_context_t ctx, decmpfs_cnode *cp, const char *xattr)
{
        /*
         *  WARNING!!!
         *  callers may (and do) pass NULL for ctx, so we should only use it
         *  for this equality comparison
         *
         *  This routine should only be called after a file has already been through decmpfs_file_is_compressed
         */

        if (ctx == decmpfs_ctx) {
                return 0;
        }
        if (strncmp(xattr, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME) - 1) == 0) {
                return decmpfs_hides_rsrc(ctx, cp);
        }
        if (!decmpfs_fast_file_is_compressed(cp)) {
                /* file is not compressed, so don't hide this xattr */
                return 0;
        }
        if (strncmp(xattr, DECMPFS_XATTR_NAME, sizeof(DECMPFS_XATTR_NAME) - 1) == 0) {
                /* it's our xattr, so hide it */
                return 1;
        }
        /* don't hide this xattr */
        return 0;
}

#pragma mark --- registration/validation routines ---

static inline int
registration_valid(const decmpfs_registration *registration)
{
        return registration && ((registration->decmpfs_registration == DECMPFS_REGISTRATION_VERSION_V1) || (registration->decmpfs_registration == DECMPFS_REGISTRATION_VERSION_V3));
}

errno_t
register_decmpfs_decompressor(uint32_t compression_type, const decmpfs_registration *registration)
{
        /* called by kexts to register decompressors */

        errno_t ret = 0;
        int locked = 0;
        char resourceName[80];

        if ((compression_type >= CMP_MAX) || !registration_valid(registration)) {
                ret = EINVAL;
                goto out;
        }

        lck_rw_lock_exclusive(decompressorsLock); locked = 1;

        /* make sure the registration for this type is zero */
        if (decompressors[compression_type] != NULL) {
                ret = EEXIST;
                goto out;
        }
        decompressors[compression_type] = registration;
        snprintf(resourceName, sizeof(resourceName), "com.apple.AppleFSCompression.Type%u", compression_type);
        IOServicePublishResource(resourceName, TRUE);

out:
        if (locked) {
                lck_rw_unlock_exclusive(decompressorsLock);
        }
        return ret;
}

errno_t
unregister_decmpfs_decompressor(uint32_t compression_type, decmpfs_registration *registration)
{
        /* called by kexts to unregister decompressors */

        errno_t ret = 0;
        int locked = 0;
        char resourceName[80];

        if ((compression_type >= CMP_MAX) || !registration_valid(registration)) {
                ret = EINVAL;
                goto out;
        }

        lck_rw_lock_exclusive(decompressorsLock); locked = 1;
        if (decompressors[compression_type] != registration) {
                ret = EEXIST;
                goto out;
        }
        decompressors[compression_type] = NULL;
        snprintf(resourceName, sizeof(resourceName), "com.apple.AppleFSCompression.Type%u", compression_type);
        IOServicePublishResource(resourceName, FALSE);

out:
        if (locked) {
                lck_rw_unlock_exclusive(decompressorsLock);
        }
        return ret;
}

static int
compression_type_valid(vnode_t vp, decmpfs_header *hdr)
{
        /* fast pre-check to determine if the given compressor has checked in */
        int ret = 0;

        /* every compressor must have at least a fetch function */
        lck_rw_lock_shared(decompressorsLock);
        if (decmp_get_func(vp, hdr->compression_type, fetch) != NULL) {
                ret = 1;
        }
        lck_rw_unlock_shared(decompressorsLock);

        return ret;
}

#pragma mark --- compression/decompression routines ---

static int
decmpfs_fetch_uncompressed_data(vnode_t vp, decmpfs_cnode *cp, decmpfs_header *hdr, off_t offset, user_ssize_t size, int nvec, decmpfs_vector *vec, uint64_t *bytes_read)
{
        /* get the uncompressed bytes for the specified region of vp by calling out to the registered compressor */

        int err          = 0;

        *bytes_read = 0;

        if ((uint64_t)offset >= hdr->uncompressed_size) {
                /* reading past end of file; nothing to do */
                err = 0;
                goto out;
        }
        if (offset < 0) {
                /* tried to read from before start of file */
                err = EINVAL;
                goto out;
        }
        if ((uint64_t)(offset + size) > hdr->uncompressed_size) {
                /* adjust size so we don't read past the end of the file */
                size = hdr->uncompressed_size - offset;
        }
        if (size == 0) {
                /* nothing to read */
                err = 0;
                goto out;
        }

        /*
         * Trace the following parameters on entry with event-id 0x03120008.
         *
         * @vp->v_id:       vnode-id of the file being decompressed.
         * @hdr->compression_type: compression type.
         * @offset:         offset from where to fetch uncompressed data.
         * @size:           amount of uncompressed data to fetch.
         *
         * Please NOTE: @offset and @size can overflow in theory but
         * here it is safe.
         */
        DECMPFS_EMIT_TRACE_ENTRY(DECMPDBG_FETCH_UNCOMPRESSED_DATA, vp->v_id,
            hdr->compression_type, (int)offset, (int)size);
        lck_rw_lock_shared(decompressorsLock);
        decmpfs_fetch_uncompressed_data_func fetch = decmp_get_func(vp, hdr->compression_type, fetch);
        if (fetch) {
                err = fetch(vp, decmpfs_ctx, hdr, offset, size, nvec, vec, bytes_read);
                lck_rw_unlock_shared(decompressorsLock);
                if (err == 0) {
                        uint64_t decompression_flags = decmpfs_cnode_get_decompression_flags(cp);
                        if (decompression_flags & DECMPFS_FLAGS_FORCE_FLUSH_ON_DECOMPRESS) {
#if     !defined(__i386__) && !defined(__x86_64__)
                                int i;
                                for (i = 0; i < nvec; i++) {
                                        flush_dcache64((addr64_t)(uintptr_t)vec[i].buf, vec[i].size, FALSE);
                                }
#endif
                        }
                }
        } else {
                err = ENOTSUP;
                lck_rw_unlock_shared(decompressorsLock);
        }
        /*
         * Trace the following parameters on return with event-id 0x03120008.
         *
         * @vp->v_id:       vnode-id of the file being decompressed.
         * @bytes_read:     amount of uncompressed bytes fetched in bytes.
         * @err:            value returned from this function.
         *
         * Please NOTE: @bytes_read can overflow in theory but here it is safe.
         */
        DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FETCH_UNCOMPRESSED_DATA, vp->v_id,
            (int)*bytes_read, err);
out:
        return err;
}

static kern_return_t
commit_upl(upl_t upl, upl_offset_t pl_offset, size_t uplSize, int flags, int abort)
{
        kern_return_t kr = 0;

#if CONFIG_IOSCHED
        upl_unmark_decmp(upl);
#endif /* CONFIG_IOSCHED */

        /* commit the upl pages */
        if (abort) {
                VerboseLog("aborting upl, flags 0x%08x\n", flags);
                kr = ubc_upl_abort_range(upl, pl_offset, uplSize, flags);
                if (kr != KERN_SUCCESS) {
                        ErrorLog("ubc_upl_abort_range error %d\n", (int)kr);
                }
        } else {
                VerboseLog("committing upl, flags 0x%08x\n", flags | UPL_COMMIT_CLEAR_DIRTY);
                kr = ubc_upl_commit_range(upl, pl_offset, uplSize, flags | UPL_COMMIT_CLEAR_DIRTY | UPL_COMMIT_WRITTEN_BY_KERNEL);
                if (kr != KERN_SUCCESS) {
                        ErrorLog("ubc_upl_commit_range error %d\n", (int)kr);
                }
        }
        return kr;
}


errno_t
decmpfs_pagein_compressed(struct vnop_pagein_args *ap, int *is_compressed, decmpfs_cnode *cp)
{
        /* handles a page-in request from vfs for a compressed file */

        int err                      = 0;
        vnode_t vp                   = ap->a_vp;
        upl_t pl                     = ap->a_pl;
        upl_offset_t pl_offset       = ap->a_pl_offset;
        off_t f_offset               = ap->a_f_offset;
        size_t size                  = ap->a_size;
        int flags                    = ap->a_flags;
        off_t uplPos                 = 0;
        user_ssize_t uplSize         = 0;
        void *data                   = NULL;
        decmpfs_header *hdr = NULL;
        uint64_t cachedSize          = 0;
        int cmpdata_locked           = 0;

        if (!decmpfs_trylock_compressed_data(cp, 0)) {
                return EAGAIN;
        }
        cmpdata_locked = 1;


        if (flags & ~(UPL_IOSYNC | UPL_NOCOMMIT | UPL_NORDAHEAD)) {
                DebugLogWithPath("pagein: unknown flags 0x%08x\n", (flags & ~(UPL_IOSYNC | UPL_NOCOMMIT | UPL_NORDAHEAD)));
        }

        err = decmpfs_fetch_compressed_header(vp, cp, &hdr, 0);
        if (err != 0) {
                goto out;
        }

        cachedSize = hdr->uncompressed_size;

        if (!compression_type_valid(vp, hdr)) {
                /* compressor not registered */
                err = ENOTSUP;
                goto out;
        }

#if CONFIG_IOSCHED
        /* Mark the UPL as the requesting UPL for decompression */
        upl_mark_decmp(pl);
#endif /* CONFIG_IOSCHED */

        /* map the upl so we can fetch into it */
        kern_return_t kr = ubc_upl_map(pl, (vm_offset_t*)&data);
        if ((kr != KERN_SUCCESS) || (data == NULL)) {
                err = ENOSPC;
                data = NULL;
#if CONFIG_IOSCHED
                upl_unmark_decmp(pl);
#endif /* CONFIG_IOSCHED */
                goto out;
        }

        uplPos = f_offset;
        uplSize = size;

        /* clip the size to the size of the file */
        if ((uint64_t)uplPos + uplSize > cachedSize) {
                /* truncate the read to the size of the file */
                uplSize = cachedSize - uplPos;
        }

        /* do the fetch */
        decmpfs_vector vec;

decompress:
        /* the mapped data pointer points to the first page of the page list, so we want to start filling in at an offset of pl_offset */
        vec.buf = (char*)data + pl_offset;
        vec.size = size;

        uint64_t did_read = 0;
        if (decmpfs_fast_get_state(cp) == FILE_IS_CONVERTING) {
                ErrorLogWithPath("unexpected pagein during decompress\n");
                /*
                 *  if the file is converting, this must be a recursive call to pagein from underneath a call to decmpfs_decompress_file;
                 *  pretend that it succeeded but don't do anything since we're just going to write over the pages anyway
                 */
                err = 0;
                did_read = 0;
        } else {
                err = decmpfs_fetch_uncompressed_data(vp, cp, hdr, uplPos, uplSize, 1, &vec, &did_read);
        }
        if (err) {
                DebugLogWithPath("decmpfs_fetch_uncompressed_data err %d\n", err);
                int cmp_state = decmpfs_fast_get_state(cp);
                if (cmp_state == FILE_IS_CONVERTING) {
                        DebugLogWithPath("cmp_state == FILE_IS_CONVERTING\n");
                        cmp_state = wait_for_decompress(cp);
                        if (cmp_state == FILE_IS_COMPRESSED) {
                                DebugLogWithPath("cmp_state == FILE_IS_COMPRESSED\n");
                                /* a decompress was attempted but it failed, let's try calling fetch again */
                                goto decompress;
                        }
                }
                if (cmp_state == FILE_IS_NOT_COMPRESSED) {
                        DebugLogWithPath("cmp_state == FILE_IS_NOT_COMPRESSED\n");
                        /* the file was decompressed after we started reading it */
                        *is_compressed = 0; /* instruct caller to fall back to its normal path */
                }
        }

        /* zero out whatever we didn't read, and zero out the end of the last page(s) */
        uint64_t total_size = (size + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
        if (did_read < total_size) {
                memset((char*)vec.buf + did_read, 0, total_size - did_read);
        }

#if CONFIG_IOSCHED
        upl_unmark_decmp(pl);
#endif /* CONFIG_IOSCHED */

        kr = ubc_upl_unmap(pl); data = NULL; /* make sure to set data to NULL so we don't try to unmap again below */
        if (kr != KERN_SUCCESS) {
                ErrorLogWithPath("ubc_upl_unmap error %d\n", (int)kr);
        } else {
                if (!err) {
                        /* commit our pages */
                        kr = commit_upl(pl, pl_offset, total_size, UPL_COMMIT_FREE_ON_EMPTY, 0);
                }
        }

out:
        if (data) {
                ubc_upl_unmap(pl);
        }
        if (hdr) {
                FREE(hdr, M_TEMP);
        }
        if (cmpdata_locked) {
                decmpfs_unlock_compressed_data(cp, 0);
        }
        if (err) {
#if 0
                if (err != ENXIO && err != ENOSPC) {
                        char *path;
                        MALLOC(path, char *, PATH_MAX, M_TEMP, M_WAITOK);
                        panic("%s: decmpfs_pagein_compressed: err %d", vnpath(vp, path, PATH_MAX), err);
                        FREE(path, M_TEMP);
                }
#endif /* 0 */
                ErrorLogWithPath("err %d\n", err);
        }
        return err;
}

errno_t
decmpfs_read_compressed(struct vnop_read_args *ap, int *is_compressed, decmpfs_cnode *cp)
{
        /* handles a read request from vfs for a compressed file */

        uio_t uio                    = ap->a_uio;
        vnode_t vp                   = ap->a_vp;
        int err                      = 0;
        int countInt                 = 0;
        off_t uplPos                 = 0;
        user_ssize_t uplSize         = 0;
        user_ssize_t uplRemaining    = 0;
        off_t curUplPos              = 0;
        user_ssize_t curUplSize      = 0;
        kern_return_t kr             = KERN_SUCCESS;
        int abort_read               = 0;
        void *data                   = NULL;
        uint64_t did_read            = 0;
        upl_t upl                    = NULL;
        upl_page_info_t *pli         = NULL;
        decmpfs_header *hdr          = NULL;
        uint64_t cachedSize          = 0;
        off_t uioPos                 = 0;
        user_ssize_t uioRemaining    = 0;
        int cmpdata_locked           = 0;

        decmpfs_lock_compressed_data(cp, 0); cmpdata_locked = 1;

        uplPos = uio_offset(uio);
        uplSize = uio_resid(uio);
        VerboseLogWithPath("uplPos %lld uplSize %lld\n", uplPos, uplSize);

        cachedSize = decmpfs_cnode_get_vnode_cached_size(cp);

        if ((uint64_t)uplPos + uplSize > cachedSize) {
                /* truncate the read to the size of the file */
                uplSize = cachedSize - uplPos;
        }

        /* give the cluster layer a chance to fill in whatever it already has */
        countInt = (uplSize > INT_MAX) ? INT_MAX : uplSize;
        err = cluster_copy_ubc_data(vp, uio, &countInt, 0);
        if (err != 0) {
                goto out;
        }

        /* figure out what's left */
        uioPos = uio_offset(uio);
        uioRemaining = uio_resid(uio);
        if ((uint64_t)uioPos + uioRemaining > cachedSize) {
                /* truncate the read to the size of the file */
                uioRemaining = cachedSize - uioPos;
        }

        if (uioRemaining <= 0) {
                /* nothing left */
                goto out;
        }

        err = decmpfs_fetch_compressed_header(vp, cp, &hdr, 0);
        if (err != 0) {
                goto out;
        }
        if (!compression_type_valid(vp, hdr)) {
                err = ENOTSUP;
                goto out;
        }

        uplPos = uioPos;
        uplSize = uioRemaining;
#if COMPRESSION_DEBUG
        DebugLogWithPath("uplPos %lld uplSize %lld\n", (uint64_t)uplPos, (uint64_t)uplSize);
#endif

        lck_rw_lock_shared(decompressorsLock);
        decmpfs_adjust_fetch_region_func adjust_fetch = decmp_get_func(vp, hdr->compression_type, adjust_fetch);
        if (adjust_fetch) {
                /* give the compressor a chance to adjust the portion of the file that we read */
                adjust_fetch(vp, decmpfs_ctx, hdr, &uplPos, &uplSize);
                VerboseLogWithPath("adjusted uplPos %lld uplSize %lld\n", (uint64_t)uplPos, (uint64_t)uplSize);
        }
        lck_rw_unlock_shared(decompressorsLock);

        /* clip the adjusted size to the size of the file */
        if ((uint64_t)uplPos + uplSize > cachedSize) {
                /* truncate the read to the size of the file */
                uplSize = cachedSize - uplPos;
        }

        if (uplSize <= 0) {
                /* nothing left */
                goto out;
        }

        /*
         *  since we're going to create a upl for the given region of the file,
         *  make sure we're on page boundaries
         */

        if (uplPos & (PAGE_SIZE - 1)) {
                /* round position down to page boundary */
                uplSize += (uplPos & (PAGE_SIZE - 1));
                uplPos &= ~(PAGE_SIZE - 1);
        }
        /* round size up to page multiple */
        uplSize = (uplSize + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);

        VerboseLogWithPath("new uplPos %lld uplSize %lld\n", (uint64_t)uplPos, (uint64_t)uplSize);

        uplRemaining = uplSize;
        curUplPos = uplPos;
        curUplSize = 0;

        while (uplRemaining > 0) {
                /* start after the last upl */
                curUplPos += curUplSize;

                /* clip to max upl size */
                curUplSize = uplRemaining;
                if (curUplSize > MAX_UPL_SIZE_BYTES) {
                        curUplSize = MAX_UPL_SIZE_BYTES;
                }

                /* create the upl */
                kr = ubc_create_upl_kernel(vp, curUplPos, curUplSize, &upl, &pli, UPL_SET_LITE, VM_KERN_MEMORY_FILE);
                if (kr != KERN_SUCCESS) {
                        ErrorLogWithPath("ubc_create_upl error %d\n", (int)kr);
                        err = EINVAL;
                        goto out;
                }
                VerboseLogWithPath("curUplPos %lld curUplSize %lld\n", (uint64_t)curUplPos, (uint64_t)curUplSize);

#if CONFIG_IOSCHED
                /* Mark the UPL as the requesting UPL for decompression */
                upl_mark_decmp(upl);
#endif /* CONFIG_IOSCHED */

                /* map the upl */
                kr = ubc_upl_map(upl, (vm_offset_t*)&data);
                if (kr != KERN_SUCCESS) {
                        commit_upl(upl, 0, curUplSize, UPL_ABORT_FREE_ON_EMPTY, 1);
#if 0
                        char *path;
                        MALLOC(path, char *, PATH_MAX, M_TEMP, M_WAITOK);
                        panic("%s: decmpfs_read_compressed: ubc_upl_map error %d", vnpath(vp, path, PATH_MAX), (int)kr);
                        FREE(path, M_TEMP);
#else /* 0 */
                        ErrorLogWithPath("ubc_upl_map kr=0x%x\n", (int)kr);
#endif /* 0 */
                        err = EINVAL;
                        goto out;
                }

                /* make sure the map succeeded */
                if (!data) {
                        commit_upl(upl, 0, curUplSize, UPL_ABORT_FREE_ON_EMPTY, 1);

                        ErrorLogWithPath("ubc_upl_map mapped null\n");
                        err = EINVAL;
                        goto out;
                }

                /* fetch uncompressed data into the mapped upl */
                decmpfs_vector vec;
decompress:
                vec = (decmpfs_vector){ .buf = data, .size = curUplSize };
                err = decmpfs_fetch_uncompressed_data(vp, cp, hdr, curUplPos, curUplSize, 1, &vec, &did_read);
                if (err) {
                        ErrorLogWithPath("decmpfs_fetch_uncompressed_data err %d\n", err);

                        /* maybe the file is converting to decompressed */
                        int cmp_state = decmpfs_fast_get_state(cp);
                        if (cmp_state == FILE_IS_CONVERTING) {
                                ErrorLogWithPath("cmp_state == FILE_IS_CONVERTING\n");
                                cmp_state = wait_for_decompress(cp);
                                if (cmp_state == FILE_IS_COMPRESSED) {
                                        ErrorLogWithPath("cmp_state == FILE_IS_COMPRESSED\n");
                                        /* a decompress was attempted but it failed, let's try fetching again */
                                        goto decompress;
                                }
                        }
                        if (cmp_state == FILE_IS_NOT_COMPRESSED) {
                                ErrorLogWithPath("cmp_state == FILE_IS_NOT_COMPRESSED\n");
                                /* the file was decompressed after we started reading it */
                                abort_read = 1; /* we're not going to commit our data */
                                *is_compressed = 0; /* instruct caller to fall back to its normal path */
                        }
                        kr = KERN_FAILURE;
                        did_read = 0;
                }
                /* zero out the remainder of the last page */
                memset((char*)data + did_read, 0, curUplSize - did_read);
                kr = ubc_upl_unmap(upl);
                if (kr == KERN_SUCCESS) {
                        if (abort_read) {
                                kr = commit_upl(upl, 0, curUplSize, UPL_ABORT_FREE_ON_EMPTY, 1);
                        } else {
                                VerboseLogWithPath("uioPos %lld uioRemaining %lld\n", (uint64_t)uioPos, (uint64_t)uioRemaining);
                                if (uioRemaining) {
                                        off_t uplOff = uioPos - curUplPos;
                                        if (uplOff < 0) {
                                                ErrorLogWithPath("uplOff %lld should never be negative\n", (int64_t)uplOff);
                                                err = EINVAL;
                                        } else {
                                                off_t count = curUplPos + curUplSize - uioPos;
                                                if (count < 0) {
                                                        /* this upl is entirely before the uio */
                                                } else {
                                                        if (count > uioRemaining) {
                                                                count = uioRemaining;
                                                        }
                                                        int io_resid = count;
                                                        err = cluster_copy_upl_data(uio, upl, uplOff, &io_resid);
                                                        int copied = count - io_resid;
                                                        VerboseLogWithPath("uplOff %lld count %lld copied %lld\n", (uint64_t)uplOff, (uint64_t)count, (uint64_t)copied);
                                                        if (err) {
                                                                ErrorLogWithPath("cluster_copy_upl_data err %d\n", err);
                                                        }
                                                        uioPos += copied;
                                                        uioRemaining -= copied;
                                                }
                                        }
                                }
                                kr = commit_upl(upl, 0, curUplSize, UPL_COMMIT_FREE_ON_EMPTY | UPL_COMMIT_INACTIVATE, 0);
                                if (err) {
                                        goto out;
                                }
                        }
                } else {
                        ErrorLogWithPath("ubc_upl_unmap error %d\n", (int)kr);
                }

                uplRemaining -= curUplSize;
        }

out:

        if (hdr) {
                FREE(hdr, M_TEMP);
        }
        if (cmpdata_locked) {
                decmpfs_unlock_compressed_data(cp, 0);
        }
        if (err) {/* something went wrong */
                ErrorLogWithPath("err %d\n", err);
                return err;
        }

#if COMPRESSION_DEBUG
        uplSize = uio_resid(uio);
        if (uplSize) {
                VerboseLogWithPath("still %lld bytes to copy\n", uplSize);
        }
#endif
        return 0;
}

int
decmpfs_free_compressed_data(vnode_t vp, decmpfs_cnode *cp)
{
        /*
         *  call out to the decompressor to free remove any data associated with this compressed file
         *  then delete the file's compression xattr
         */
        decmpfs_header *hdr = NULL;

        /*
         * Trace the following parameters on entry with event-id 0x03120010.
         *
         * @vp->v_id:       vnode-id of the file for which to free compressed data.
         */
        DECMPFS_EMIT_TRACE_ENTRY(DECMPDBG_FREE_COMPRESSED_DATA, vp->v_id);

        int err = decmpfs_fetch_compressed_header(vp, cp, &hdr, 0);
        if (err) {
                ErrorLogWithPath("decmpfs_fetch_compressed_header err %d\n", err);
        } else {
                lck_rw_lock_shared(decompressorsLock);
                decmpfs_free_compressed_data_func free_data = decmp_get_func(vp, hdr->compression_type, free_data);
                if (free_data) {
                        err = free_data(vp, decmpfs_ctx, hdr);
                } else {
                        /* nothing to do, so no error */
                        err = 0;
                }
                lck_rw_unlock_shared(decompressorsLock);

                if (err != 0) {
                        ErrorLogWithPath("decompressor err %d\n", err);
                }
        }
        /*
         * Trace the following parameters on return with event-id 0x03120010.
         *
         * @vp->v_id:       vnode-id of the file for which to free compressed data.
         * @err:            value returned from this function.
         */
        DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_FREE_COMPRESSED_DATA, vp->v_id, err);

        /* delete the xattr */
        err = vn_removexattr(vp, DECMPFS_XATTR_NAME, 0, decmpfs_ctx);
        if (err != 0) {
                goto out;
        }

out:
        if (hdr) {
                FREE(hdr, M_TEMP);
        }
        return err;
}

#pragma mark --- file conversion routines ---

static int
unset_compressed_flag(vnode_t vp)
{
        int err = 0;
        struct vnode_attr va;
        int new_bsdflags = 0;

        VATTR_INIT(&va);
        VATTR_WANTED(&va, va_flags);
        err = vnode_getattr(vp, &va, decmpfs_ctx);

        if (err != 0) {
                ErrorLogWithPath("vnode_getattr err %d\n", err);
        } else {
                new_bsdflags = va.va_flags & ~UF_COMPRESSED;

                VATTR_INIT(&va);
                VATTR_SET(&va, va_flags, new_bsdflags);
                err = vnode_setattr(vp, &va, decmpfs_ctx);
                if (err != 0) {
                        ErrorLogWithPath("vnode_setattr err %d\n", err);
                }
        }
        return err;
}

int
decmpfs_decompress_file(vnode_t vp, decmpfs_cnode *cp, off_t toSize, int truncate_okay, int skiplock)
{
        /* convert a compressed file to an uncompressed file */

        int err                      = 0;
        char *data                   = NULL;
        uio_t uio_w                  = 0;
        off_t offset                 = 0;
        uint32_t old_state           = 0;
        uint32_t new_state           = 0;
        int update_file_state        = 0;
        int allocSize                = 0;
        decmpfs_header *hdr          = NULL;
        int cmpdata_locked           = 0;
        off_t remaining              = 0;
        uint64_t uncompressed_size   = 0;

        /*
         * Trace the following parameters on entry with event-id 0x03120000.
         *
         * @vp->v_id:           vnode-id of the file being decompressed.
         * @toSize:             uncompress given bytes of the file.
         * @truncate_okay:      on error it is OK to truncate.
         * @skiplock:           compressed data is locked, skip locking again.
         *
         * Please NOTE: @toSize can overflow in theory but here it is safe.
         */
        DECMPFS_EMIT_TRACE_ENTRY(DECMPDBG_DECOMPRESS_FILE, vp->v_id,
            (int)toSize, truncate_okay, skiplock);

        if (!skiplock) {
                decmpfs_lock_compressed_data(cp, 1); cmpdata_locked = 1;
        }

decompress:
        old_state = decmpfs_fast_get_state(cp);

        switch (old_state) {
        case FILE_IS_NOT_COMPRESSED:
        {
                /* someone else decompressed the file */
                err = 0;
                goto out;
        }

        case FILE_TYPE_UNKNOWN:
        {
                /* the file is in an unknown state, so update the state and retry */
                (void)decmpfs_file_is_compressed(vp, cp);

                /* try again */
                goto decompress;
        }

        case FILE_IS_COMPRESSED:
        {
                /* the file is compressed, so decompress it */
                break;
        }

        default:
        {
                /*
                 *  this shouldn't happen since multiple calls to decmpfs_decompress_file lock each other out,
                 *  and when decmpfs_decompress_file returns, the state should be always be set back to
                 *  FILE_IS_NOT_COMPRESSED or FILE_IS_UNKNOWN
                 */
                err = EINVAL;
                goto out;
        }
        }

        err = decmpfs_fetch_compressed_header(vp, cp, &hdr, 0);
        if (err != 0) {
                goto out;
        }

        uncompressed_size = hdr->uncompressed_size;
        if (toSize == -1) {
                toSize = hdr->uncompressed_size;
        }

        if (toSize == 0) {
                /* special case truncating the file to zero bytes */
                goto nodecmp;
        } else if ((uint64_t)toSize > hdr->uncompressed_size) {
                /* the caller is trying to grow the file, so we should decompress all the data */
                toSize = hdr->uncompressed_size;
        }

        allocSize = MIN(64 * 1024, toSize);
        MALLOC(data, char *, allocSize, M_TEMP, M_WAITOK);
        if (!data) {
                err = ENOMEM;
                goto out;
        }

        uio_w = uio_create(1, 0LL, UIO_SYSSPACE, UIO_WRITE);
        if (!uio_w) {
                err = ENOMEM;
                goto out;
        }
        uio_w->uio_flags |= UIO_FLAGS_IS_COMPRESSED_FILE;

        remaining = toSize;

        /* tell the buffer cache that this is an empty file */
        ubc_setsize(vp, 0);

        /* if we got here, we need to decompress the file */
        decmpfs_cnode_set_vnode_state(cp, FILE_IS_CONVERTING, 1);

        while (remaining > 0) {
                /* loop decompressing data from the file and writing it into the data fork */

                uint64_t bytes_read = 0;
                decmpfs_vector vec = { .buf = data, .size = MIN(allocSize, remaining) };
                err = decmpfs_fetch_uncompressed_data(vp, cp, hdr, offset, vec.size, 1, &vec, &bytes_read);
                if (err != 0) {
                        ErrorLogWithPath("decmpfs_fetch_uncompressed_data err %d\n", err);
                        goto out;
                }

                if (bytes_read == 0) {
                        /* we're done reading data */
                        break;
                }

                uio_reset(uio_w, offset, UIO_SYSSPACE, UIO_WRITE);
                err = uio_addiov(uio_w, CAST_USER_ADDR_T(data), bytes_read);
                if (err != 0) {
                        ErrorLogWithPath("uio_addiov err %d\n", err);
                        err = ENOMEM;
                        goto out;
                }

                err = VNOP_WRITE(vp, uio_w, 0, decmpfs_ctx);
                if (err != 0) {
                        /* if the write failed, truncate the file to zero bytes */
                        ErrorLogWithPath("VNOP_WRITE err %d\n", err);
                        break;
                }
                offset += bytes_read;
                remaining -= bytes_read;
        }

        if (err == 0) {
                if (offset != toSize) {
                        ErrorLogWithPath("file decompressed to %lld instead of %lld\n", offset, toSize);
                        err = EINVAL;
                        goto out;
                }
        }

        if (err == 0) {
                /* sync the data and metadata */
                err = VNOP_FSYNC(vp, MNT_WAIT, decmpfs_ctx);
                if (err != 0) {
                        ErrorLogWithPath("VNOP_FSYNC err %d\n", err);
                        goto out;
                }
        }

        if (err != 0) {
                /* write, setattr, or fsync failed */
                ErrorLogWithPath("aborting decompress, err %d\n", err);
                if (truncate_okay) {
                        /* truncate anything we might have written */
                        int error = vnode_setsize(vp, 0, 0, decmpfs_ctx);
                        ErrorLogWithPath("vnode_setsize err %d\n", error);
                }
                goto out;
        }

nodecmp:
        /* if we're truncating the file to zero bytes, we'll skip ahead to here */

        /* unset the compressed flag */
        unset_compressed_flag(vp);

        /* free the compressed data associated with this file */
        err = decmpfs_free_compressed_data(vp, cp);
        if (err != 0) {
                ErrorLogWithPath("decmpfs_free_compressed_data err %d\n", err);
        }

        /*
         *  even if free_compressed_data or vnode_getattr/vnode_setattr failed, return success
         *  since we succeeded in writing all of the file data to the data fork
         */
        err = 0;

        /* if we got this far, the file was successfully decompressed */
        update_file_state = 1;
        new_state = FILE_IS_NOT_COMPRESSED;

#if COMPRESSION_DEBUG
        {
                uint64_t filesize = 0;
                vnsize(vp, &filesize);
                DebugLogWithPath("new file size %lld\n", filesize);
        }
#endif

out:
        if (hdr) {
                FREE(hdr, M_TEMP);
        }
        if (data) {
                FREE(data, M_TEMP);
        }
        if (uio_w) {
                uio_free(uio_w);
        }

        if (err != 0) {
                /* if there was a failure, reset compression flags to unknown and clear the buffer cache data */
                update_file_state = 1;
                new_state = FILE_TYPE_UNKNOWN;
                if (uncompressed_size) {
                        ubc_setsize(vp, 0);
                        ubc_setsize(vp, uncompressed_size);
                }
        }

        if (update_file_state) {
                lck_mtx_lock(decompress_channel_mtx);
                decmpfs_cnode_set_vnode_state(cp, new_state, 1);
                wakeup((caddr_t)&decompress_channel); /* wake up anyone who might have been waiting for decompression */
                lck_mtx_unlock(decompress_channel_mtx);
        }

        if (cmpdata_locked) {
                decmpfs_unlock_compressed_data(cp, 1);
        }
        /*
         * Trace the following parameters on return with event-id 0x03120000.
         *
         * @vp->v_id:   vnode-id of the file being decompressed.
         * @err:        value returned from this function.
         */
        DECMPFS_EMIT_TRACE_RETURN(DECMPDBG_DECOMPRESS_FILE, vp->v_id, err);
        return err;
}

#pragma mark --- Type1 compressor ---

/*
 *  The "Type1" compressor stores the data fork directly in the compression xattr
 */

static int
decmpfs_validate_compressed_file_Type1(__unused vnode_t vp, __unused vfs_context_t ctx, decmpfs_header *hdr)
{
        int err          = 0;

        if (hdr->uncompressed_size + sizeof(decmpfs_disk_header) != (uint64_t)hdr->attr_size) {
                err = EINVAL;
                goto out;
        }
out:
        return err;
}

static int
decmpfs_fetch_uncompressed_data_Type1(__unused vnode_t vp, __unused vfs_context_t ctx, decmpfs_header *hdr, off_t offset, user_ssize_t size, int nvec, decmpfs_vector *vec, uint64_t *bytes_read)
{
        int err          = 0;
        int i;
        user_ssize_t remaining;

        if (hdr->uncompressed_size + sizeof(decmpfs_disk_header) != (uint64_t)hdr->attr_size) {
                err = EINVAL;
                goto out;
        }

#if COMPRESSION_DEBUG
        static int dummy = 0; // prevent syslog from coalescing printfs
        DebugLogWithPath("%d memcpy %lld at %lld\n", dummy++, size, (uint64_t)offset);
#endif

        remaining = size;
        for (i = 0; (i < nvec) && (remaining > 0); i++) {
                user_ssize_t curCopy = vec[i].size;
                if (curCopy > remaining) {
                        curCopy = remaining;
                }
                memcpy(vec[i].buf, hdr->attr_bytes + offset, curCopy);
                offset += curCopy;
                remaining -= curCopy;
        }

        if ((bytes_read) && (err == 0)) {
                *bytes_read = (size - remaining);
        }

out:
        return err;
}

SECURITY_READ_ONLY_EARLY(static decmpfs_registration) Type1Reg =
{
        .decmpfs_registration = DECMPFS_REGISTRATION_VERSION,
        .validate          = decmpfs_validate_compressed_file_Type1,
        .adjust_fetch      = NULL,/* no adjust necessary */
        .fetch             = decmpfs_fetch_uncompressed_data_Type1,
        .free_data         = NULL,/* no free necessary */
        .get_flags         = NULL/* no flags */
};

#pragma mark --- decmpfs initialization ---

void
decmpfs_init()
{
        static int done = 0;
        if (done) {
                return;
        }

        decmpfs_ctx = vfs_context_create(vfs_context_kernel());

        lck_grp_attr_t *attr = lck_grp_attr_alloc_init();
        decmpfs_lockgrp = lck_grp_alloc_init("VFSCOMP", attr);
        lck_grp_attr_free(attr);
        decompressorsLock = lck_rw_alloc_init(decmpfs_lockgrp, NULL);
        decompress_channel_mtx = lck_mtx_alloc_init(decmpfs_lockgrp, NULL);

        register_decmpfs_decompressor(CMP_Type1, &Type1Reg);

        done = 1;
}
#endif /* FS_COMPRESSION */