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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2012-07-30 14:42:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-30 17:25:19 -0700
commitfe0627e7b3d32a41c16fac6e0af091991545865e (patch)
treed2b358827dff033691a5ce145334f7e3f7b0c5bf
parent278038ac53c6c4f53d1d34f978beb9aba1410b2c (diff)
nilfs2: fix timing issue between rmcp and chcp ioctls
The checkpoint deletion ioctl (rmcp ioctl) has potential for breaking snapshot because it is not fully exclusive with checkpoint mode change ioctl (chcp ioctl). The rmcp ioctl first tests if the specified checkpoint is a snapshot or not within nilfs_cpfile_delete_checkpoint function, and then calls nilfs_cpfile_delete_checkpoints function to actually invalidate the checkpoint only if it's not a snapshot. However, the checkpoint can be changed into a snapshot by the chcp ioctl between these two operations. In that case, calling nilfs_cpfile_delete_checkpoints() wrongly invalidates the snapshot, which leads to snapshot list corruption and snapshot count mismatch. This fixes the issue by changing nilfs_cpfile_delete_checkpoints() so that it reconfirms the target checkpoints are snapshot or not. This second check is exclusive with the chcp operation since it is protected by an existing semaphore. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/nilfs2/cpfile.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c
index dab5c4c6dfaf..deaa3d33a0aa 100644
--- a/fs/nilfs2/cpfile.c
+++ b/fs/nilfs2/cpfile.c
@@ -286,7 +286,7 @@ int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
__u64 cno;
void *kaddr;
unsigned long tnicps;
- int ret, ncps, nicps, count, i;
+ int ret, ncps, nicps, nss, count, i;
if (unlikely(start == 0 || start > end)) {
printk(KERN_ERR "%s: invalid range of checkpoint numbers: "
@@ -301,6 +301,7 @@ int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
if (ret < 0)
goto out_sem;
tnicps = 0;
+ nss = 0;
for (cno = start; cno < end; cno += ncps) {
ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
@@ -318,8 +319,9 @@ int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
cpfile, cno, cp_bh, kaddr);
nicps = 0;
for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
- WARN_ON(nilfs_checkpoint_snapshot(cp));
- if (!nilfs_checkpoint_invalid(cp)) {
+ if (nilfs_checkpoint_snapshot(cp)) {
+ nss++;
+ } else if (!nilfs_checkpoint_invalid(cp)) {
nilfs_checkpoint_set_invalid(cp);
nicps++;
}
@@ -364,6 +366,8 @@ int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
}
brelse(header_bh);
+ if (nss > 0)
+ ret = -EBUSY;
out_sem:
up_write(&NILFS_MDT(cpfile)->mi_sem);