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authorStefan Behrens <sbehrens@giantdisaster.de>2013-10-15 22:08:15 +0400
committerBen Hutchings <ben@decadent.org.uk>2014-05-18 17:58:07 +0400
commit8bbfb31d6b0eef58364978299a90bb37dc8e01f0 (patch)
tree505e9e56daa05a70ea5aa846ba3caae4f13817d2
parent27b34b28a13e98b2e61559afd00ae5d9d18c5e82 (diff)
downloadlinux-8bbfb31d6b0eef58364978299a90bb37dc8e01f0.tar.xz
Btrfs: Don't allocate inode that is already in use
commit ff76b0565523319d7c1c0b51d5a5a8915d33efab upstream. Due to an off-by-one error, it is possible to reproduce a bug when the inode cache is used. The same inode number is assigned twice, the second time this leads to an EEXIST in btrfs_insert_empty_items(). The issue can happen when a file is removed right after a subvolume is created and then a new inode number is created before the inodes in free_inode_pinned are processed. unlink() calls btrfs_return_ino() which calls start_caching() in this case which adds [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID] by searching for the highest inode (which already cannot find the unlinked one anymore in btrfs_find_free_objectid()). So if this unlinked inode's number is equal to the highest_ino + 1 (or >= this value instead of > this value which was the off-by-one error), we mustn't add the inode number to free_ino_pinned (caching_thread() does it right). In this case we need to try directly to add the number to the inode_cache which will fail in this case. When this inode number is allocated while it is still in free_ino_pinned, it is allocated and still added to the free inode cache when the pinned inodes are processed, thus one of the following inode number allocations will get an inode that is already in use and fail with EEXIST in btrfs_insert_empty_items(). One example which was created with the reproducer below: Create a snapshot, work in the newly created snapshot for the rest. In unlink(inode 34284) call btrfs_return_ino() which calls start_caching(). start_caching() calls add_free_space [34284, 18446744073709517077]. In btrfs_return_ino(), call start_caching pinned [34284, 1] which is wrong. mkdir() call btrfs_find_ino_for_alloc() which returns the number 34284. btrfs_unpin_free_ino calls add_free_space [34284, 1]. mkdir() call btrfs_find_ino_for_alloc() which returns the number 34284. EEXIST when the new inode is inserted. One possible reproducer is this one: #!/bin/sh # preparation TEST_DEV=/dev/sdc1 TEST_MNT=/mnt umount ${TEST_MNT} 2>/dev/null || true mkfs.btrfs -f ${TEST_DEV} mount ${TEST_DEV} ${TEST_MNT} -o \ rw,relatime,compress=lzo,space_cache,inode_cache btrfs subv create ${TEST_MNT}/s1 for i in `seq 34027`; do touch ${TEST_MNT}/s1/${i}; done btrfs subv snap ${TEST_MNT}/s1 ${TEST_MNT}/s2 FILENAME=`find ${TEST_MNT}/s1/ -inum 4085 | sed 's|^.*/\([^/]*\)$|\1|'` rm ${TEST_MNT}/s2/$FILENAME touch ${TEST_MNT}/s2/$FILENAME # the following steps can be repeated to reproduce the issue again and again [ -e ${TEST_MNT}/s3 ] && btrfs subv del ${TEST_MNT}/s3 btrfs subv snap ${TEST_MNT}/s2 ${TEST_MNT}/s3 rm ${TEST_MNT}/s3/$FILENAME touch ${TEST_MNT}/s3/$FILENAME ls -alFi ${TEST_MNT}/s?/$FILENAME touch ${TEST_MNT}/s3/_1 || logger FAILED ls -alFi ${TEST_MNT}/s?/_1 touch ${TEST_MNT}/s3/_2 || logger FAILED ls -alFi ${TEST_MNT}/s?/_2 touch ${TEST_MNT}/s3/__1 || logger FAILED ls -alFi ${TEST_MNT}/s?/__1 touch ${TEST_MNT}/s3/__2 || logger FAILED ls -alFi ${TEST_MNT}/s?/__2 # if the above is not enough, add the following loop: for i in `seq 3 9`; do touch ${TEST_MNT}/s3/__${i} || logger FAILED; done #for i in `seq 3 34027`; do touch ${TEST_MNT}/s3/__${i} || logger FAILED; done # one of the touch(1) calls in s3 fail due to EEXIST because the inode is # already in use that btrfs_find_ino_for_alloc() returns. Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de> Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--fs/btrfs/inode-map.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index f8962a957d65..6d4038b9c0c3 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -237,7 +237,7 @@ again:
start_caching(root);
if (objectid <= root->cache_progress ||
- objectid > root->highest_objectid)
+ objectid >= root->highest_objectid)
__btrfs_add_free_space(ctl, objectid, 1);
else
__btrfs_add_free_space(pinned, objectid, 1);