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

btrfs: handle logged extent failure properly

2020-02-28T16:23:29Z

commit bd727173e4432fe6cb70ba108dc1f3602c5409d7 upstream. If we're allocating a logged extent we attempt to insert an extent record for the file extent directly. We increase space_info->bytes_reserved, because the extent entry addition will call btrfs_update_block_group(), which will convert the ->bytes_reserved to ->bytes_used. However if we fail at any point while inserting the extent entry we will bail and leave space on ->bytes_reserved, which will trigger a WARN_ON() on umount. Fix this by pinning the space if we fail to insert, which is what happens in every other failure case that involves adding the extent entry. CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Johannes Thumshirn Reviewed-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

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: handle error in btrfs_cache_block_group

2019-12-13T13:09:22Z

We have a BUG_ON(ret < 0) in find_free_extent from btrfs_cache_block_group. If we fail to allocate our ctl we'll just panic, which is not good. Instead just go on to another block group. If we fail to find a block group we don't want to return ENOSPC, because really we got a ENOMEM and that's the root of the problem. Save our return from btrfs_cache_block_group(), and then if we still fail to make our allocation return that ret so we get the right error back. Tested with inject-error.py from bcc. Reviewed-by: Johannes Thumshirn Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: rename btrfs_block_group_cache

2019-11-18T16:51:51Z

The type name is misleading, a single entry is named 'cache' while this normally means a collection of objects. Rename that everywhere. Also the identifier was quite long, making function prototypes harder to format. Suggested-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: Ensure we trim ranges across block group boundary

2019-11-18T16:51:48Z

[BUG] When deleting large files (which cross block group boundary) with discard mount option, we find some btrfs_discard_extent() calls only trimmed part of its space, not the whole range: btrfs_discard_extent: type=0x1 start=19626196992 len=2144530432 trimmed=1073741824 ratio=50% type: bbio->map_type, in above case, it's SINGLE DATA. start: Logical address of this trim len: Logical length of this trim trimmed: Physically trimmed bytes ratio: trimmed / len Thus leaving some unused space not discarded. [CAUSE] When discard mount option is specified, after a transaction is fully committed (super block written to disk), we begin to cleanup pinned extents in the following call chain: btrfs_commit_transaction() |- btrfs_finish_extent_commit() |- find_first_extent_bit(unpin, 0, &start, &end, EXTENT_DIRTY); |- btrfs_discard_extent() However, pinned extents are recorded in an extent_io_tree, which can merge adjacent extent states. When a large file gets deleted and it has adjacent file extents across block group boundary, we will get a large merged range like this: |<--- BG1 --->|<--- BG2 --->| |//////|<-- Range to discard --->|/////| To discard that range, we have the following calls: btrfs_discard_extent() |- btrfs_map_block() | Returned bbio will end at BG1's end. As btrfs_map_block() | never returns result across block group boundary. |- btrfs_issuse_discard() Issue discard for each stripe. So we will only discard the range in BG1, not the remaining part in BG2. Furthermore, this bug is not that reliably observed, for above case, if there is no other extent in BG2, BG2 will be empty and btrfs will trim all space of BG2, covering up the bug. [FIX] - Allow __btrfs_map_block_for_discard() to modify @length parameter btrfs_map_block() uses its @length paramter to notify the caller how many bytes are mapped in current call. With __btrfs_map_block_for_discard() also modifing the @length, btrfs_discard_extent() now understands when to do extra trim. - Call btrfs_map_block() in a loop until we hit the range end Since we now know how many bytes are mapped each time, we can iterate through each block group boundary and issue correct trim for each range. Reviewed-by: Filipe Manana Reviewed-by: Nikolay Borisov Tested-by: Nikolay Borisov Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: add dedicated members for start and length of a block group

2019-11-18T16:51:45Z

The on-disk format of block group item makes use of the key that stores the offset and length. This is further used in the code, although this makes thing harder to understand. The key is also packed so the offset/length is not properly aligned as u64. Add start (key.objectid) and length (key.offset) members to block group and remove the embedded key. When the item is searched or written, a local variable for key is used. Reviewed-by: Johannes Thumshirn Reviewed-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: move block_group_item::used to block group

2019-11-18T16:51:44Z

For unknown reasons, the member 'used' in the block group struct is stored in the b-tree item and accessed everywhere using the special accessor helper. Let's unify it and make it a regular member and only update the item before writing it to the tree. The item is still being used for flags and chunk_objectid, there's some duplication until the item is removed in following patches. Reviewed-by: Johannes Thumshirn Reviewed-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: User assert to document transaction requirement

2019-11-18T11:46:54Z

Using an ASSERT in btrfs_pin_extent allows to more stringently observe whether the function is called under a transaction or not. Reviewed-by: Johannes Thumshirn Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba 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: refactor the ticket wakeup code

2019-09-09T12:59:18Z

Now that btrfs_space_info_add_old_bytes simply checks if we can make the reservation and updates bytes_may_use, there's no reason to have both helpers in place. Factor out the ticket wakeup logic into it's own helper, make btrfs_space_info_add_old_bytes() update bytes_may_use and then call the wakeup helper, and replace all calls to btrfs_space_info_add_new_bytes() with the wakeup helper. Reviewed-by: Nikolay Borisov Signed-off-by: Josef Bacik Signed-off-by: David Sterba