kernel.git/fs/btrfs/tree-log.c, branch linux-5.5.y

Btrfs: fix infinite loop during fsync after rename operations

2020-02-11T12:37:03Z

commit b5e4ff9d465da1233a2d9a47ebce487c70d8f4ab upstream. Recently fsstress (from fstests) sporadically started to trigger an infinite loop during fsync operations. This turned out to be because support for the rename exchange and whiteout operations was added to fsstress in fstests. These operations, unlike any others in fsstress, cause file names to be reused, whence triggering this issue. However it's not necessary to use rename exchange and rename whiteout operations trigger this issue, simple rename operations and file creations are enough to trigger the issue. The issue boils down to when we are logging inodes that conflict (that had the name of any inode we need to log during the fsync operation), we keep logging them even if they were already logged before, and after that we check if there's any other inode that conflicts with them and then add it again to the list of inodes to log. Skipping already logged inodes fixes the issue. Consider the following example: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ mkdir /mnt/testdir # inode 257 $ touch /mnt/testdir/zz # inode 258 $ ln /mnt/testdir/zz /mnt/testdir/zz_link $ touch /mnt/testdir/a # inode 259 $ sync # The following 3 renames achieve the same result as a rename exchange # operation ( /mnt/testdir/zz_link to /mnt/testdir/a). $ mv /mnt/testdir/a /mnt/testdir/a/tmp $ mv /mnt/testdir/zz_link /mnt/testdir/a $ mv /mnt/testdir/a/tmp /mnt/testdir/zz_link # The following rename and file creation give the same result as a # rename whiteout operation ( zz to a2). $ mv /mnt/testdir/zz /mnt/testdir/a2 $ touch /mnt/testdir/zz # inode 260 $ xfs_io -c fsync /mnt/testdir/zz --> results in the infinite loop The following steps happen: 1) When logging inode 260, we find that its reference named "zz" was used by inode 258 in the previous transaction (through the commit root), so inode 258 is added to the list of conflicting indoes that need to be logged; 2) After logging inode 258, we find that its reference named "a" was used by inode 259 in the previous transaction, and therefore we add inode 259 to the list of conflicting inodes to be logged; 3) After logging inode 259, we find that its reference named "zz_link" was used by inode 258 in the previous transaction - we add inode 258 to the list of conflicting inodes to log, again - we had already logged it before at step 3. After logging it again, we find again that inode 259 conflicts with him, and we add again 259 to the list, etc - we end up repeating all the previous steps. So fix this by skipping logging of conflicting inodes that were already logged. Fixes: 6b5fc433a7ad67 ("Btrfs: fix fsync after succession of renames of different files") CC: stable@vger.kernel.org # 5.1+ Signed-off-by: Filipe Manana Reviewed-by: Josef Bacik Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

Btrfs: fix missing hole after hole punching and fsync when using NO_HOLES

2020-02-11T12:37:03Z

commit 0e56315ca147b3e60c7bf240233a301d3c7fb508 upstream. When using the NO_HOLES feature, if we punch a hole into a file and then fsync it, there are cases where a subsequent fsync will miss the fact that a hole was punched, resulting in the holes not existing after replaying the log tree. Essentially these cases all imply that, tree-log.c:copy_items(), is not invoked for the leafs that delimit holes, because nothing changed those leafs in the current transaction. And it's precisely copy_items() where we currenly detect and log holes, which works as long as the holes are between file extent items in the input leaf or between the beginning of input leaf and the previous leaf or between the last item in the leaf and the next leaf. First example where we miss a hole: *) The extent items of the inode span multiple leafs; *) The punched hole covers a range that affects only the extent items of the first leaf; *) The fsync operation is done in full mode (BTRFS_INODE_NEEDS_FULL_SYNC is set in the inode's runtime flags). That results in the hole not existing after replaying the log tree. For example, if the fs/subvolume tree has the following layout for a particular inode: Leaf N, generation 10: [ ... INODE_ITEM INODE_REF EXTENT_ITEM (0 64K) EXTENT_ITEM (64K 128K) ] Leaf N + 1, generation 10: [ EXTENT_ITEM (128K 64K) ... ] If at transaction 11 we punch a hole coverting the range [0, 128K[, we end up dropping the two extent items from leaf N, but we don't touch the other leaf, so we end up in the following state: Leaf N, generation 11: [ ... INODE_ITEM INODE_REF ] Leaf N + 1, generation 10: [ EXTENT_ITEM (128K 64K) ... ] A full fsync after punching the hole will only process leaf N because it was modified in the current transaction, but not leaf N + 1, since it was not modified in the current transaction (generation 10 and not 11). As a result the fsync will not log any holes, because it didn't process any leaf with extent items. Second example where we will miss a hole: *) An inode as its items spanning 5 (or more) leafs; *) A hole is punched and it covers only the extents items of the 3rd leaf. This resulsts in deleting the entire leaf and not touching any of the other leafs. So the only leaf that is modified in the current transaction, when punching the hole, is the first leaf, which contains the inode item. During the full fsync, the only leaf that is passed to copy_items() is that first leaf, and that's not enough for the hole detection code in copy_items() to determine there's a hole between the last file extent item in the 2nd leaf and the first file extent item in the 3rd leaf (which was the 4th leaf before punching the hole). Fix this by scanning all leafs and punch holes as necessary when doing a full fsync (less common than a non-full fsync) when the NO_HOLES feature is enabled. The lack of explicit file extent items to mark holes makes it necessary to scan existing extents to determine if holes exist. A test case for fstests follows soon. Fixes: 16e7549f045d33 ("Btrfs: incompatible format change to remove hole extents") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: skip log replay on orphaned roots

2019-12-13T13:10:45Z

My fsstress modifications coupled with generic/475 uncovered a failure to mount and replay the log if we hit a orphaned root. We do not want to replay the log for an orphan root, but it's completely legitimate to have an orphaned root with a log attached. Fix this by simply skipping replaying the log. We still need to pin it's root node so that we do not overwrite it while replaying other logs, as we re-read the log root at every stage of the replay. CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Filipe Manana Signed-off-by: Josef Bacik Signed-off-by: David Sterba

Btrfs: fix missing data checksums after replaying a log tree

2019-12-13T13:09:24Z

When logging a file that has shared extents (reflinked with other files or with itself), we can end up logging multiple checksum items that cover overlapping ranges. This confuses the search for checksums at log replay time causing some checksums to never be added to the fs/subvolume tree. Consider the following example of a file that shares the same extent at offsets 0 and 256Kb: [ bytenr 13893632, offset 64Kb, len 64Kb ] 0 64Kb [ bytenr 13631488, offset 64Kb, len 192Kb ] 64Kb 256Kb [ bytenr 13893632, offset 0, len 256Kb ] 256Kb 512Kb When logging the inode, at tree-log.c:copy_items(), when processing the file extent item at offset 0, we log a checksum item covering the range 13959168 to 14024704, which corresponds to 13893632 + 64Kb and 13893632 + 64Kb + 64Kb, respectively. Later when processing the extent item at offset 256K, we log the checksums for the range from 13893632 to 14155776 (which corresponds to 13893632 + 256Kb). These checksums get merged with the checksum item for the range from 13631488 to 13893632 (13631488 + 256Kb), logged by a previous fsync. So after this we get the two following checksum items in the log tree: (...) item 6 key (EXTENT_CSUM EXTENT_CSUM 13631488) itemoff 3095 itemsize 512 range start 13631488 end 14155776 length 524288 item 7 key (EXTENT_CSUM EXTENT_CSUM 13959168) itemoff 3031 itemsize 64 range start 13959168 end 14024704 length 65536 The first one covers the range from the second one, they overlap. So far this does not cause a problem after replaying the log, because when replaying the file extent item for offset 256K, we copy all the checksums for the extent 13893632 from the log tree to the fs/subvolume tree, since searching for an checksum item for bytenr 13893632 leaves us at the first checksum item, which covers the whole range of the extent. However if we write 64Kb to file offset 256Kb for example, we will not be able to find and copy the checksums for the last 128Kb of the extent at bytenr 13893632, referenced by the file range 384Kb to 512Kb. After writing 64Kb into file offset 256Kb we get the following extent layout for our file: [ bytenr 13893632, offset 64K, len 64Kb ] 0 64Kb [ bytenr 13631488, offset 64Kb, len 192Kb ] 64Kb 256Kb [ bytenr 14155776, offset 0, len 64Kb ] 256Kb 320Kb [ bytenr 13893632, offset 64Kb, len 192Kb ] 320Kb 512Kb After fsync'ing the file, if we have a power failure and then mount the filesystem to replay the log, the following happens: 1) When replaying the file extent item for file offset 320Kb, we lookup for the checksums for the extent range from 13959168 (13893632 + 64Kb) to 14155776 (13893632 + 256Kb), through a call to btrfs_lookup_csums_range(); 2) btrfs_lookup_csums_range() finds the checksum item that starts precisely at offset 13959168 (item 7 in the log tree, shown before); 3) However that checksum item only covers 64Kb of data, and not 192Kb of data; 4) As a result only the checksums for the first 64Kb of data referenced by the file extent item are found and copied to the fs/subvolume tree. The remaining 128Kb of data, file range 384Kb to 512Kb, doesn't get the corresponding data checksums found and copied to the fs/subvolume tree. 5) After replaying the log userspace will not be able to read the file range from 384Kb to 512Kb, because the checksums are missing and resulting in an -EIO error. The following steps reproduce this scenario: $ mkfs.btrfs -f /dev/sdc $ mount /dev/sdc /mnt/sdc $ xfs_io -f -c "pwrite -S 0xa3 0 256K" /mnt/sdc/foobar $ xfs_io -c "fsync" /mnt/sdc/foobar $ xfs_io -c "pwrite -S 0xc7 256K 256K" /mnt/sdc/foobar $ xfs_io -c "reflink /mnt/sdc/foobar 320K 0 64K" /mnt/sdc/foobar $ xfs_io -c "fsync" /mnt/sdc/foobar $ xfs_io -c "pwrite -S 0xe5 256K 64K" /mnt/sdc/foobar $ xfs_io -c "fsync" /mnt/sdc/foobar $ mount /dev/sdc /mnt/sdc $ md5sum /mnt/sdc/foobar md5sum: /mnt/sdc/foobar: Input/output error $ dmesg | tail [165305.003464] BTRFS info (device sdc): no csum found for inode 257 start 401408 [165305.004014] BTRFS info (device sdc): no csum found for inode 257 start 405504 [165305.004559] BTRFS info (device sdc): no csum found for inode 257 start 409600 [165305.005101] BTRFS info (device sdc): no csum found for inode 257 start 413696 [165305.005627] BTRFS info (device sdc): no csum found for inode 257 start 417792 [165305.006134] BTRFS info (device sdc): no csum found for inode 257 start 421888 [165305.006625] BTRFS info (device sdc): no csum found for inode 257 start 425984 [165305.007278] BTRFS info (device sdc): no csum found for inode 257 start 430080 [165305.008248] BTRFS warning (device sdc): csum failed root 5 ino 257 off 393216 csum 0x1337385e expected csum 0x00000000 mirror 1 [165305.009550] BTRFS warning (device sdc): csum failed root 5 ino 257 off 393216 csum 0x1337385e expected csum 0x00000000 mirror 1 Fix this simply by deleting first any checksums, from the log tree, for the range of the extent we are logging at copy_items(). This ensures we do not get checksum items in the log tree that have overlapping ranges. This is a long time issue that has been present since we have the clone (and deduplication) ioctl, and can happen both when an extent is shared between different files and within the same file. A test case for fstests follows soon. CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: opencode extent_buffer_get

2019-11-18T11:46:54Z

The helper is trivial and we can understand what the atomic_inc on something named refs does. Reviewed-by: Johannes Thumshirn Reviewed-by: Anand Jain Signed-off-by: David Sterba

btrfs: drop unused parameter is_new from btrfs_iget

2019-11-18T11:46:52Z

The parameter is now always set to NULL and could be dropped. The last user was get_default_root but that got reworked in 05dbe6837b60 ("Btrfs: unify subvol= and subvolid= mounting") and the parameter became unused. Reviewed-by: Anand Jain Signed-off-by: David Sterba

btrfs: Open-code name_in_log_ref in replay_one_name

2019-11-18T11:46:51Z

That function adds unnecessary indirection between backref_in_log and the caller. Furthermore it also "downgrades" backref_in_log's return value to a boolean, when in fact it could very well be an error. Rectify the situation by simply opencoding name_in_log_ref in replay_one_name and properly handling possible return codes from backref_in_log. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba [ update comment ] Signed-off-by: David Sterba

btrfs: Properly handle backref_in_log retval

2019-11-18T11:46:51Z

This function can return a negative error value if btrfs_search_slot errors for whatever reason or if btrfs_alloc_path runs out of memory. This is currently problemattic because backref_in_log is treated by its callers as if it returns boolean. Fix this by adding proper error handling in callers. That also enables the function to return the direct error code from btrfs_search_slot. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: Don't opencode btrfs_find_name_in_backref in backref_in_log

2019-11-18T11:46:51Z

Direct replacement, though note that the inside of the loop in btrfs_find_name_in_backref is organized in a slightly different way but is equvalent. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba [ add changelog ] Signed-off-by: David Sterba

Merge tag 'for-5.4-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2019-10-10T15:30:51Z

Pull btrfs fixes from David Sterba: "A few more stabitly fixes, one build warning fix. - fix inode allocation under NOFS context - fix leak in fiemap due to concurrent append writes - fix log-root tree updates - fix balance convert of single profile on 32bit architectures - silence false positive warning on old GCCs (code moved in rc1)" * tag 'for-5.4-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: silence maybe-uninitialized warning in clone_range btrfs: fix uninitialized ret in ref-verify btrfs: allocate new inode in NOFS context btrfs: fix balance convert to single on 32-bit host CPUs btrfs: fix incorrect updating of log root tree Btrfs: fix memory leak due to concurrent append writes with fiemap