xnu-2422.1.72.tar.gz

[apple/xnu.git] / bsd / hfs / hfscommon / BTree / BTreeNodeReserve.c

diff --git a/bsd/hfs/hfscommon/BTree/BTreeNodeReserve.c b/bsd/hfs/hfscommon/BTree/BTreeNodeReserve.c
index e58dde4e6564e03fbcb03a954b9933e9b1ad5d58..94577758a1d7da705c82287ad81e34ee460c6e99 100644 (file)
--- a/bsd/hfs/hfscommon/BTree/BTreeNodeReserve.c
+++ b/bsd/hfs/hfscommon/BTree/BTreeNodeReserve.c
@@ -153,12 +153,28 @@ BTReserveSpace(FCB *file, int operations, void* data)
        
        if (rsrvNodes > availNodes) {
                u_int32_t reqblks, freeblks, rsrvblks;
+               uint32_t bt_rsrv;
                struct hfsmount *hfsmp;
 
-               /* Try and reserve the last 5% of the disk space for file blocks. */
+               /* 
+                * For UNIX conformance, we try and reserve the MIN of either 5% of 
+                * total file blocks or 10MB worth of blocks, for growing existing 
+                * files.  On non-HFS filesystems, creating a new directory entry may
+                * not cause additional disk space to be allocated, but on HFS, creating
+                * a new entry could cause the b-tree to grow.  As a result, we take 
+                * some precautions here to prevent that on configurations that try to 
+                * satisfy conformance.
+                */
                hfsmp = VTOVCB(btree->fileRefNum);
                rsrvblks = ((u_int64_t)hfsmp->allocLimit * 5) / 100;
-               rsrvblks = MIN(rsrvblks, HFS_MAXRESERVE / hfsmp->blockSize);
+               if (hfsmp->blockSize > HFS_BT_MAXRESERVE) {
+                       bt_rsrv = 1;    
+               }
+               else {
+                       bt_rsrv = (HFS_BT_MAXRESERVE / hfsmp->blockSize);
+               }
+               rsrvblks = MIN(rsrvblks, bt_rsrv);      
+               
                freeblks = hfs_freeblks(hfsmp, 0);
                if (freeblks <= rsrvblks) {
                        /* When running low, disallow adding new items. */