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authorFilipe Manana <fdmanana@suse.com>2015-06-20 18:20:09 +0100
committerFilipe Manana <fdmanana@suse.com>2015-07-11 22:33:14 +0100
commitc1aa45759e90b4204ab8bce027a925fc7c87d00a (patch)
tree42bea0bd8b1dd00ae3d12e673be706e35cbca381 /fs
parent9689457b5b0a2b69874c421a489d3fb50ca76b7b (diff)
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Btrfs: fix shrinking truncate when the no_holes feature is enabled
If the no_holes feature is enabled, we attempt to shrink a file to a size that ends up in the middle of a hole and we don't have any file extent items in the fs/subvol tree that go beyond the new file size (or any ordered extents that will insert such file extent items), we end up not updating the inode's disk_i_size, we only update the inode's i_size. This means that after unmounting and mounting the filesystem, or after the inode is evicted and reloaded, its i_size ends up being incorrect (an inode's i_size is set to the disk_i_size field when an inode is loaded). This happens when btrfs_truncate_inode_items() doesn't find any file extent items to drop - in this case it never makes a call to btrfs_ordered_update_i_size() in order to update the inode's disk_i_size. Example reproducer: $ mkfs.btrfs -O no-holes -f /dev/sdd $ mount /dev/sdd /mnt # Create our test file with some data and durably persist it. $ xfs_io -f -c "pwrite -S 0xaa 0 128K" /mnt/foo $ sync # Append some data to the file, increasing its size, and leave a hole # between the old size and the start offset if the following write. So # our file gets a hole in the range [128Kb, 256Kb[. $ xfs_io -c "truncate 160K" /mnt/foo # We expect to see our file with a size of 160Kb, with the first 128Kb # of data all having the value 0xaa and the remaining 32Kb of data all # having the value 0x00. $ od -t x1 /mnt/foo 0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa * 0400000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 * 0500000 # Now cleanly unmount and mount again the filesystem. $ umount /mnt $ mount /dev/sdd /mnt # We expect to get the same result as before, a file with a size of # 160Kb, with the first 128Kb of data all having the value 0xaa and the # remaining 32Kb of data all having the value 0x00. $ od -t x1 /mnt/foo 0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa * 0400000 In the example above the file size/data do not match what they were before the remount. Fix this by always calling btrfs_ordered_update_i_size() with a size matching the size the file was truncated to if btrfs_truncate_inode_items() is not called for a log tree and no file extent items were dropped. This ensures the same behaviour as when the no_holes feature is not enabled. A test case for fstests follows soon. Signed-off-by: Filipe Manana <fdmanana@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/inode.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b33c0cf02668..e33dff356460 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4209,7 +4209,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
u64 extent_num_bytes = 0;
u64 extent_offset = 0;
u64 item_end = 0;
- u64 last_size = (u64)-1;
+ u64 last_size = new_size;
u32 found_type = (u8)-1;
int found_extent;
int del_item;
@@ -4493,8 +4493,7 @@ out:
btrfs_abort_transaction(trans, root, ret);
}
error:
- if (last_size != (u64)-1 &&
- root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
+ if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
btrfs_ordered_update_i_size(inode, last_size, NULL);
btrfs_free_path(path);