xnu-4903.270.47.tar.gz

[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 */