aboutsummaryrefslogtreecommitdiffstats
path: root/fs/xfs
diff options
context:
space:
mode:
authorDavid Chinner <dgc@sgi.com>2008-04-28 22:53:32 -0400
committerLachlan McIlroy <lachlan@redback.melbourne.sgi.com>2008-04-29 01:58:56 -0400
commit359346a9655c8800408ed3ca44517ac7ea95c197 (patch)
tree4a97c2956dc5204fd28c26008bbf1f27c1e684bf /fs/xfs
parent86c4d62305649848164ae311a0959fc569b0d964 (diff)
[XFS] Don't initialise new inode generation numbers to zero
When we allocation new inode chunks, we initialise the generation numbers to zero. This works fine until we delete a chunk and then reallocate it, resulting in the same inode numbers but with a reset generation count. This can result in inode/generation pairs of different inodes occurring relatively close together. Given that the inode/gen pair makes up the "unique" portion of an NFS filehandle on XFS, this can result in file handles cached on clients being seen on the wire from the server but refer to a different file. This causes .... issues for NFS clients. Hence we need a unique generation number initialisation for each inode to prevent reuse of a small portion of the generation number space. Use a random number to initialise the generation number so we don't need to keep any new state on disk whilst making the new number difficult to guess from previous allocations. SGI-PV: 979416 SGI-Modid: xfs-linux-melb:xfs-kern:31001a Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/xfs_ialloc.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c
index a64dfbd565a5..aad8c5da38af 100644
--- a/fs/xfs/xfs_ialloc.c
+++ b/fs/xfs/xfs_ialloc.c
@@ -147,6 +147,7 @@ xfs_ialloc_ag_alloc(
147 int version; /* inode version number to use */ 147 int version; /* inode version number to use */
148 int isaligned = 0; /* inode allocation at stripe unit */ 148 int isaligned = 0; /* inode allocation at stripe unit */
149 /* boundary */ 149 /* boundary */
150 unsigned int gen;
150 151
151 args.tp = tp; 152 args.tp = tp;
152 args.mp = tp->t_mountp; 153 args.mp = tp->t_mountp;
@@ -290,6 +291,14 @@ xfs_ialloc_ag_alloc(
290 else 291 else
291 version = XFS_DINODE_VERSION_1; 292 version = XFS_DINODE_VERSION_1;
292 293
294 /*
295 * Seed the new inode cluster with a random generation number. This
296 * prevents short-term reuse of generation numbers if a chunk is
297 * freed and then immediately reallocated. We use random numbers
298 * rather than a linear progression to prevent the next generation
299 * number from being easily guessable.
300 */
301 gen = random32();
293 for (j = 0; j < nbufs; j++) { 302 for (j = 0; j < nbufs; j++) {
294 /* 303 /*
295 * Get the block. 304 * Get the block.
@@ -309,6 +318,7 @@ xfs_ialloc_ag_alloc(
309 free = XFS_MAKE_IPTR(args.mp, fbuf, i); 318 free = XFS_MAKE_IPTR(args.mp, fbuf, i);
310 free->di_core.di_magic = cpu_to_be16(XFS_DINODE_MAGIC); 319 free->di_core.di_magic = cpu_to_be16(XFS_DINODE_MAGIC);
311 free->di_core.di_version = version; 320 free->di_core.di_version = version;
321 free->di_core.di_gen = cpu_to_be32(gen);
312 free->di_next_unlinked = cpu_to_be32(NULLAGINO); 322 free->di_next_unlinked = cpu_to_be32(NULLAGINO);
313 xfs_ialloc_log_di(tp, fbuf, i, 323 xfs_ialloc_log_di(tp, fbuf, i,
314 XFS_DI_CORE_BITS | XFS_DI_NEXT_UNLINKED); 324 XFS_DI_CORE_BITS | XFS_DI_NEXT_UNLINKED);