xnu-1504.3.12.tar.gz

[apple/xnu.git] / bsd / vfs / vfs_cluster.c

diff --git a/bsd/vfs/vfs_cluster.c b/bsd/vfs/vfs_cluster.c
index 5aec1498a48a26d7480d7a8ec7c7176177659475..d436d781baa3ce22544f7b859ac49bfdf5d63b46 100644 (file)
--- a/bsd/vfs/vfs_cluster.c
+++ b/bsd/vfs/vfs_cluster.c
@@ -2718,7 +2718,7 @@ cluster_write_copy(vnode_t vp, struct uio *uio, u_int32_t io_req_size, off_t old
                         * because IO_HEADZEROFILL and IO_TAILZEROFILL not set
                         */
                        if ((start_offset + total_size) > max_io_size)
-                               total_size -= start_offset;
+                               total_size = max_io_size - start_offset;
                        xfer_resid = total_size;
 
                        retval = cluster_copy_ubc_data_internal(vp, uio, &xfer_resid, 1, 1);
@@ -5614,6 +5614,14 @@ is_file_clean(vnode_t vp, off_t filesize)
 #define DRT_HASH_SMALL_MODULUS 23
 #define DRT_HASH_LARGE_MODULUS 401
 
+/*
+ * Physical memory required before the large hash modulus is permitted.
+ *
+ * On small memory systems, the large hash modulus can lead to phsyical
+ * memory starvation, so we avoid using it there.
+ */
+#define DRT_HASH_LARGE_MEMORY_REQUIRED (1024LL * 1024LL * 1024LL)      /* 1GiB */
+
 #define DRT_SMALL_ALLOCATION   1024    /* 104 bytes spare */
 #define DRT_LARGE_ALLOCATION   16384   /* 344 bytes spare */
 
@@ -5756,8 +5764,12 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
                 * see whether we should grow to the large one.
                 */
                if (ocmap->scm_modulus == DRT_HASH_SMALL_MODULUS) {
-                       /* if the ring is nearly full */
-                       if (active_buckets > (DRT_HASH_SMALL_MODULUS - 5)) {
+                       /* 
+                        * If the ring is nearly full and we are allowed to
+                        * use the large modulus, upgrade.
+                        */
+                       if ((active_buckets > (DRT_HASH_SMALL_MODULUS - 5)) &&
+                           (max_mem >= DRT_HASH_LARGE_MEMORY_REQUIRED)) {
                                nsize = DRT_HASH_LARGE_MODULUS;
                        } else {
                                nsize = DRT_HASH_SMALL_MODULUS;