kernel.git/fs/btrfs/delayed-ref.c, branch linux-6.15.y

btrfs: update tree_insert() to use rb helpers

2025-01-13T13:53:18Z

Update tree_insert() to use rb_find_add_cached(). add cmp_refs_node in rb_find_add_cached() to compare. Since we're here, also make comp_data_refs() and comp_refs() accept both parameters as const. Signed-off-by: Roger L. Beckermeyer III Reviewed-by: Qu Wenruo Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: drop fs_info argument from btrfs_update_space_info_*()

2025-01-13T13:53:14Z

Since commit e1e577aafe41 ("btrfs: store fs_info in space_info"), we have the fs_info in a space_info. So, we can drop fs_info argument from btrfs_update_space_info_*. There is no behavior change. Reviewed-by: Johannes Thumshirn Signed-off-by: Naohiro Aota Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: selftests: add delayed ref self test cases

2025-01-13T13:53:13Z

The recent fix for a stupid mistake I made uncovered the fact that we don't have adequate testing in the delayed refs code, as it took a pretty extensive and long running stress test to uncover something that a unit test would have uncovered right away. Fix this by adding a delayed refs self test suite. This will validate that the btrfs_ref transformation does the correct thing, that we do the correct thing when merging delayed refs, and that we get the delayed refs in the order that we expect. These are all crucial to how the delayed refs operate. I introduced various bugs (including the original bug) into the delayed refs code to validate that these tests caught all of the shenanigans that I could think of. Reviewed-by: Boris Burkov Signed-off-by: Josef Bacik Signed-off-by: David Sterba

btrfs: move select_delayed_ref() and export it

2025-01-13T13:53:13Z

This helper is how we select the delayed ref to run once we've selected the delayed ref head. I need this exported to add a unit test for delayed refs, and it's more natural home is in delayed-ref.c. Rename it to btrfs_select_delayed_ref and move it into delayed-ref.c. Reviewed-by: Boris Burkov Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba

Merge tag 'for-6.13-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2024-11-19T00:37:41Z

Pull btrfs updates from David Sterba: "Changes outside of btrfs: add io_uring command flag to track a dying task (the rest will go via the block git tree). User visible changes: - wire encoded read (ioctl) to io_uring commands, this can be used on itself, in the future this will allow 'send' to be asynchronous. As a consequence, the encoded read ioctl can also work in non-blocking mode - new ioctl to wait for cleaned subvolumes, no need to use the generic and root-only SEARCH_TREE ioctl, will be used by "btrfs subvol sync" - recognize different paths/symlinks for the same devices and don't report them during rescanning, this can be observed with LVM or DM - seeding device use case change, the sprout device (the one capturing new writes) will not clear the read-only status of the super block; this prevents accumulating space from deleted snapshots Performance improvements: - reduce lock contention when traversing extent buffers - reduce extent tree lock contention when searching for inline backref - switch from rb-trees to xarray for delayed ref tracking, improvements due to better cache locality, branching factors and more compact data structures - enable extent map shrinker again (prevent memory exhaustion under some types of IO load), reworked to run in a single worker thread (there used to be problems causing long stalls under memory pressure) Core changes: - raid-stripe-tree feature updates: - make device replace and scrub work - implement partial deletion of stripe extents - new selftests - split the config option BTRFS_DEBUG and add EXPERIMENTAL for features that are experimental or with known problems so we don't misuse debugging config for that - subpage mode updates (sector < page): - update compression implementations - update writepage, writeback - continued folio API conversions: - buffered writes - make buffered write copy one page at a time, preparatory work for future integration with large folios, may cause performance drop - proper locking of root item regarding starting send - error handling improvements - code cleanups and refactoring: - dead code removal - unused parameter reduction - lockdep assertions" * tag 'for-6.13-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (119 commits) btrfs: send: check for read-only send root under critical section btrfs: send: check for dead send root under critical section btrfs: remove check for NULL fs_info at btrfs_folio_end_lock_bitmap() btrfs: fix warning on PTR_ERR() against NULL device at btrfs_control_ioctl() btrfs: fix a typo in btrfs_use_zone_append btrfs: avoid superfluous calls to free_extent_map() in btrfs_encoded_read() btrfs: simplify logic to decrement snapshot counter at btrfs_mksnapshot() btrfs: remove hole from struct btrfs_delayed_node btrfs: update stale comment for struct btrfs_delayed_ref_node::add_list btrfs: add new ioctl to wait for cleaned subvolumes btrfs: simplify range tracking in cow_file_range() btrfs: remove conditional path allocation in btrfs_read_locked_inode() btrfs: push cleanup into btrfs_read_locked_inode() io_uring/cmd: let cmds to know about dying task btrfs: add struct io_btrfs_cmd as type for io_uring_cmd_to_pdu() btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl) btrfs: move priv off stack in btrfs_encoded_read_regular_fill_pages() btrfs: don't sleep in btrfs_encoded_read() if IOCB_NOWAIT is set btrfs: change btrfs_encoded_read() so that reading of extent is done by caller btrfs: remove pointless iocb::ki_pos addition in btrfs_encoded_read() ...

btrfs: fix incorrect comparison for delayed refs

2024-11-14T15:11:02Z

When I reworked delayed ref comparison in cf4f04325b2b ("btrfs: move ->parent and ->ref_root into btrfs_delayed_ref_node"), I made a mistake and returned -1 for the case where ref1->ref_root was > than ref2->ref_root. This is a subtle bug that can result in improper delayed ref running order, which can result in transaction aborts. Fixes: cf4f04325b2b ("btrfs: move ->parent and ->ref_root into btrfs_delayed_ref_node") CC: stable@vger.kernel.org # 6.10+ Reviewed-by: Filipe Manana Reviewed-by: Qu Wenruo Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: remove no longer used delayed ref head search functionality

2024-11-11T13:34:21Z

After the previous patch, which converted the rb-tree used to track delayed ref heads into an xarray, the find_ref_head() function is now used only by one caller which always passes false to the 'return_bigger' argument. So remove the 'return_bigger' logic, simplifying the function, and move all the function code to the single caller. Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: track delayed ref heads in an xarray

2024-11-11T13:34:21Z

Currently we use a red black tree (rb-tree) to track the delayed ref heads (in struct btrfs_delayed_ref_root::href_root). This however is not very efficient when the number of delayed ref heads is large (and it's very common to be at least in the order of thousands) since rb-trees are binary trees. For example for 10K delayed ref heads, the tree has a depth of 13. Besides that, inserting into the tree requires navigating through it and pulling useless cache lines in the process since the red black tree nodes are embedded within the delayed ref head structure - on the other hand, by being embedded, it requires no extra memory allocations. We can improve this by using an xarray instead which has a much higher branching factor than a red black tree (binary balanced tree) and is more cache friendly and behaves like a resizable array, with a much better search and insertion complexity than a red black tree. This only has one small disadvantage which is that insertion will sometimes require allocating memory for the xarray - which may fail (not that often since it uses a kmem_cache) - but on the other hand we can reduce the delayed ref head structure size by 24 bytes (from 152 down to 128 bytes) after removing the embedded red black tree node, meaning than we can now fit 32 delayed ref heads per 4K page instead of 26, and that gain compensates for the occasional memory allocations needed for the xarray nodes. We also end up using only 2 cache lines instead of 3 per delayed ref head. Running the following fs_mark test showed some improvements: $ cat test.sh #!/bin/bash DEV=/dev/nullb0 MNT=/mnt/nullb0 MOUNT_OPTIONS="-o ssd" FILES=100000 THREADS=$(nproc --all) echo "performance" | \ tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor mkfs.btrfs -f $DEV mount $MOUNT_OPTIONS $DEV $MNT OPTS="-S 0 -L 5 -n $FILES -s 0 -t $THREADS -k" for ((i = 1; i <= $THREADS; i++)); do OPTS="$OPTS -d $MNT/d$i" done fs_mark $OPTS umount $MNT Before this patch: FSUse% Count Size Files/sec App Overhead 10 1200000 0 171845.7 12253839 16 2400000 0 230898.7 12308254 23 3600000 0 212292.9 12467768 30 4800000 0 195737.8 12627554 46 6000000 0 171055.2 12783329 After this patch: FSUse% Count Size Files/sec App Overhead 10 1200000 0 173835.0 12246131 16 2400000 0 233537.8 12271746 23 3600000 0 220398.7 12307737 30 4800000 0 204483.6 12392318 40 6000000 0 182923.3 12771843 Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: assert delayed refs lock is held at add_delayed_ref_head()

2024-11-11T13:34:20Z

The delayed refs lock must be held when calling add_delayed_ref_head(), so assert that it's being held. Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: assert delayed refs lock is held at find_first_ref_head()

2024-11-11T13:34:20Z

The delayed refs lock must be held when calling find_first_ref_head(), so assert that it's being held. Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba