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linux/fs/btrfs
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JP Kobryn (Meta) 7ae37b2c94 btrfs: prevent direct reclaim during compressed readahead 
Under memory pressure, direct reclaim can kick in during compressed
readahead. This puts the associated task into D-state. Then shrink_lruvec()
disables interrupts when acquiring the LRU lock. Under heavy pressure,
we've observed reclaim can run long enough that the CPU becomes prone to
CSD lock stalls since it cannot service incoming IPIs. Although the CSD
lock stalls are the worst case scenario, we have found many more subtle
occurrences of this latency on the order of seconds, over a minute in some
cases.

Prevent direct reclaim during compressed readahead. This is achieved by
using different GFP flags at key points when the bio is marked for
readahead.

There are two functions that allocate during compressed readahead:
btrfs_alloc_compr_folio() and add_ra_bio_pages(). Both currently use
GFP_NOFS which includes __GFP_DIRECT_RECLAIM.

For the internal API call btrfs_alloc_compr_folio(), the signature changes
to accept an additional gfp_t parameter. At the readahead call site, it
gets flags similar to GFP_NOFS but stripped of __GFP_DIRECT_RECLAIM.
__GFP_NOWARN is added since these allocations are allowed to fail. Demand
reads still use full GFP_NOFS and will enter reclaim if needed. All other
existing call sites of btrfs_alloc_compr_folio() now explicitly pass
GFP_NOFS to retain their current behavior.

add_ra_bio_pages() gains a bool parameter which allows callers to specify
if they want to allow direct reclaim or not. In either case, the
__GFP_NOWARN flag was added unconditionally since the allocations are
speculative.

There has been some previous work done on calling add_ra_bio_pages() [0].
This patch is complementary: where that patch reduces call frequency, this
patch reduces the latency associated with those calls.

[0] https://lore.kernel.org/linux-btrfs/656838ec1232314a2657716e59f4f15a8eadba64.1751492111.git.boris@bur.io/

Reviewed-by: Mark Harmstone <mark@harmstone.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: JP Kobryn (Meta) <jp.kobryn@linux.dev>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
History 2026-04-07 18:56:08 +02:00
..
tests btrfs: replace kcalloc() calls to kzalloc_objs() 2026-04-07 18:55:59 +02:00
accessors.c btrfs: fix typos in comments and strings 2025-09-23 08:49:16 +02:00
accessors.h btrfs: allow mounting filesystems with remap-tree incompat flag 2026-02-03 07:54:35 +01:00
acl.c posix_acl: make posix_acl_to_xattr() alloc the buffer 2026-01-16 10:51:12 +01:00
acl.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
async-thread.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
async-thread.h btrfs: add forward declarations and headers, part 1 2024-03-04 16:24:49 +01:00
backref.c btrfs: remove redundant extent_buffer_uptodate() checks after read_tree_block() 2026-04-07 18:55:55 +02:00
backref.h btrfs: declare free_ipath() via DEFINE_FREE() 2025-11-24 22:34:51 +01:00
bio.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
bio.h btrfs: move existing remaps before relocating block group 2026-02-03 07:54:35 +01:00
block-group.c btrfs: replace BUG_ON() with error return in cache_save_setup() 2026-04-07 18:56:08 +02:00
block-group.h btrfs: zoned: limit number of zones reclaimed in flush_space() 2026-04-07 18:56:01 +02:00
block-rsv.c btrfs: don't allow log trees to consume global reserve or overcommit metadata 2026-04-07 18:55:53 +02:00
block-rsv.h btrfs: add METADATA_REMAP chunk type 2026-02-03 07:54:27 +01:00
btrfs_inode.h fsverity: use a hashtable to find the fsverity_info 2026-02-04 11:31:54 -08:00
compression.c btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00
compression.h btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00
ctree.c btrfs: rename local variable for offset in folio 2026-04-07 18:56:07 +02:00
ctree.h btrfs: introduce BTRFS_PATH_AUTO_RELEASE() helper 2026-02-03 06:38:32 +01:00
defrag.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
defrag.h btrfs: pass struct btrfs_inode to btrfs_defrag_file() 2025-03-18 20:35:43 +01:00
delalloc-space.c btrfs: remove fs_info argument from btrfs_reserve_metadata_bytes() 2025-11-24 21:59:11 +01:00
delalloc-space.h btrfs: pass struct btrfs_inode to btrfs_free_reserved_data_space_noquota() 2025-05-15 14:30:52 +02:00
delayed-inode.c btrfs: unexport btrfs_qgroup_reserve_meta() 2026-04-07 18:56:05 +02:00
delayed-inode.h btrfs: embed delayed root to struct btrfs_fs_info 2026-02-03 07:56:20 +01:00
delayed-ref.c btrfs: zoned: cap delayed refs metadata reservation to avoid overcommit 2026-04-07 18:55:55 +02:00
delayed-ref.h btrfs: move ref-verify under CONFIG_BTRFS_DEBUG 2025-09-22 10:54:32 +02:00
dev-replace.c btrfs: pass literal booleans to functions that take boolean arguments 2026-04-07 18:55:56 +02:00
dev-replace.h btrfs: trivial conversion to return bool instead of int 2025-05-15 14:30:49 +02:00
dir-item.c btrfs: remove pointless error check in btrfs_check_dir_item_collision() 2026-04-07 18:56:00 +02:00
dir-item.h btrfs: rename inode number parameter passed to btrfs_check_dir_item_collision() 2025-07-22 00:05:00 +02:00
direct-io.c btrfs: remove redundant nowait check in lock_extent_direct() 2026-04-07 18:55:58 +02:00
direct-io.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
discard.c btrfs: handle discarding fully-remapped block groups 2026-02-03 07:54:36 +01:00
discard.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
disk-io.c btrfs: remove atomic parameter from btrfs_buffer_uptodate() 2026-04-07 18:56:02 +02:00
disk-io.h btrfs: remove atomic parameter from btrfs_buffer_uptodate() 2026-04-07 18:56:02 +02:00
export.c btrfs: avoid potential out-of-bounds in btrfs_encode_fh() 2025-09-26 08:48:30 +02:00
export.h btrfs: add forward declarations and headers, part 1 2024-03-04 16:24:49 +01:00
extent-io-tree.c btrfs: avoid GFP_ATOMIC allocations in qgroup free paths 2026-04-07 18:56:05 +02:00
extent-io-tree.h btrfs: convert several int parameters to bool 2025-09-22 10:54:32 +02:00
extent-tree.c btrfs: decrease indentation of find_free_extent_update_loop 2026-04-07 18:56:05 +02:00
extent-tree.h btrfs: add do_remap parameter to btrfs_discard_extent() 2026-02-03 07:54:35 +01:00
extent_io.c btrfs: use common eb range validation in read_extent_buffer_to_user_nofault() 2026-04-07 18:56:07 +02:00
extent_io.h btrfs: avoid GFP_ATOMIC allocations in qgroup free paths 2026-04-07 18:56:05 +02:00
extent_map.c btrfs: add strict extent map alignment checks 2026-02-03 07:56:19 +01:00
extent_map.h btrfs: headers cleanup to remove unnecessary local includes 2025-11-24 22:34:52 +01:00
fiemap.c Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
fiemap.h btrfs: move fiemap code into its own file 2024-07-11 15:33:20 +02:00
file-item.c btrfs: rename btrfs_csum_file_blocks() to btrfs_insert_data_csums() 2026-04-07 18:55:56 +02:00
file-item.h btrfs: rename btrfs_csum_file_blocks() to btrfs_insert_data_csums() 2026-04-07 18:55:56 +02:00
file.c btrfs: pass literal booleans to functions that take boolean arguments 2026-04-07 18:55:56 +02:00
file.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
free-space-cache.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
free-space-cache.h btrfs: handle discarding fully-remapped block groups 2026-02-03 07:54:36 +01:00
free-space-tree.c btrfs: check for NULL root after calls to btrfs_extent_root() 2026-03-17 11:22:49 +01:00
free-space-tree.h btrfs: handle setting up relocation of block group with remap-tree 2026-02-03 07:54:35 +01:00
fs.c btrfs: switch to library APIs for checksums 2026-02-03 06:38:32 +01:00
fs.h btrfs: report filesystem shutdown via fserror 2026-04-07 18:55:59 +02:00
inode-item.c btrfs: merge setting ret and return ret 2026-02-03 06:38:33 +01:00
inode-item.h btrfs: remove unused parameters from btrfs_lookup_inode_extref() 2025-07-21 23:58:03 +02:00
inode.c btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00
ioctl.c btrfs: fix btrfs_ioctl_space_info() slot_count TOCTOU which can lead to info-leak 2026-04-07 18:56:05 +02:00
ioctl.h tree-wide: s/struct fileattr/struct file_kattr/g 2025-07-04 16:14:39 +02:00
Kconfig btrfs: move shutdown and remove_bdev callbacks out of experimental features 2026-04-07 18:56:05 +02:00
locking.c btrfs: add definitions and constants for remap-tree 2026-02-03 07:54:02 +01:00
locking.h btrfs: fix typos in comments and strings 2025-09-23 08:49:16 +02:00
lru_cache.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
lru_cache.h btrfs: cleanup recursive include of the same header 2024-07-11 15:33:22 +02:00
lzo.c btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00
Makefile btrfs: tests: zoned: add tests cases for zoned code 2026-04-07 18:55:52 +02:00
messages.c btrfs: pass level to _btrfs_printk() to avoid parsing level from string 2026-02-03 07:49:10 +01:00
messages.h btrfs: stop printing condition result in assertion failure messages 2026-04-07 18:55:58 +02:00
misc.h btrfs: introduce a common helper to calculate the size of a bio 2026-04-07 18:55:59 +02:00
ordered-data.c btrfs: output more info when duplicated ordered extent is found 2026-04-07 18:56:02 +02:00
ordered-data.h btrfs: check type flags in alloc_ordered_extent() 2026-04-07 18:56:02 +02:00
orphan.c btrfs: BTRFS_PATH_AUTO_FREE in orphan.c 2024-09-10 16:51:22 +02:00
orphan.h btrfs: add forward declarations and headers, part 1 2024-03-04 16:24:49 +01:00
print-tree.c btrfs: remove redundant extent_buffer_uptodate() checks after read_tree_block() 2026-04-07 18:55:55 +02:00
print-tree.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
props.c btrfs: props: switch prop_handler::extract to struct btrfs_inode 2025-03-18 20:35:44 +01:00
props.h btrfs: pass struct btrfs_inode to btrfs_inode_inherit_props() 2025-03-18 20:35:44 +01:00
qgroup.c btrfs: avoid GFP_ATOMIC allocations in qgroup free paths 2026-04-07 18:56:05 +02:00
qgroup.h btrfs: unexport btrfs_qgroup_reserve_meta() 2026-04-07 18:56:05 +02:00
raid-stripe-tree.c btrfs: fix placement of unlikely() in btrfs_insert_one_raid_extent() 2026-04-07 18:55:58 +02:00
raid-stripe-tree.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
raid56.c btrfs: replace kcalloc() calls to kzalloc_objs() 2026-04-07 18:55:59 +02:00
raid56.h btrfs: raid56: introduce a new parameter to locate a sector 2025-11-25 01:46:58 +01:00
ref-verify.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
ref-verify.h btrfs: move ref-verify under CONFIG_BTRFS_DEBUG 2025-09-22 10:54:32 +02:00
reflink.c btrfs: fix deadlock between reflink and transaction commit when using flushoncommit 2026-04-07 18:56:06 +02:00
reflink.h btrfs: add forward declarations and headers, part 1 2024-03-04 16:24:49 +01:00
relocation.c btrfs: avoid starting new transaction and commit in relocate_block_group() 2026-04-07 18:55:55 +02:00
relocation.h btrfs: handle setting up relocation of block group with remap-tree 2026-02-03 07:54:35 +01:00
root-tree.c btrfs: fix lost error return in btrfs_find_orphan_roots() 2026-02-18 15:25:54 +01:00
root-tree.h btrfs: qgroup: fix qgroup prealloc rsv leak in subvolume operations 2024-04-02 19:18:23 +02:00
scrub.c btrfs: introduce a common helper to calculate the size of a bio 2026-04-07 18:55:59 +02:00
scrub.h btrfs: convert several int parameters to bool 2025-09-22 10:54:32 +02:00
send.c btrfs: pass literal booleans to functions that take boolean arguments 2026-04-07 18:55:56 +02:00
send.h btrfs: pass btrfs_root pointers to send ioctl parameters 2025-03-18 20:35:49 +01:00
space-info.c btrfs: zoned: limit number of zones reclaimed in flush_space() 2026-04-07 18:56:01 +02:00
space-info.h btrfs: constify arguments of some functions 2026-04-07 18:55:58 +02:00
subpage.c for-6.19-tag 2025-12-03 20:03:46 -08:00
subpage.h btrfs: headers cleanup to remove unnecessary local includes 2025-11-24 22:34:52 +01:00
super.c btrfs: move shutdown and remove_bdev callbacks out of experimental features 2026-04-07 18:56:05 +02:00
super.h btrfs: constify arguments of some functions 2026-04-07 18:55:58 +02:00
sysfs.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
sysfs.h btrfs: remove fs_info argument from btrfs_sysfs_add_space_info_type() 2025-11-24 22:02:30 +01:00
transaction.c btrfs: prefer IS_ERR_OR_NULL() over manual NULL check 2026-04-07 18:56:02 +02:00
transaction.h btrfs: inhibit extent buffer writeback to prevent COW amplification 2026-04-07 18:56:00 +02:00
tree-checker.c btrfs: tree-checker: add remap-tree checks to check_block_group_item() 2026-04-07 18:56:06 +02:00
tree-checker.h btrfs: add definitions and constants for remap-tree 2026-02-03 07:54:02 +01:00
tree-log.c btrfs: make btrfs_free_log() and btrfs_free_log_root_tree() return void 2026-04-07 18:56:06 +02:00
tree-log.h btrfs: make btrfs_free_log() and btrfs_free_log_root_tree() return void 2026-04-07 18:56:06 +02:00
tree-mod-log.c btrfs: remove redundant extent_buffer_uptodate() checks after read_tree_block() 2026-04-07 18:55:55 +02:00
tree-mod-log.h btrfs: drop unused parameter path from btrfs_tree_mod_log_rewind() 2024-11-11 14:34:15 +01:00
ulist.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
ulist.h btrfs: preallocate ulist memory for qgroup rsv 2024-07-11 15:33:26 +02:00
uuid-tree.c btrfs: prefer IS_ERR_OR_NULL() over manual NULL check 2026-04-07 18:56:02 +02:00
uuid-tree.h btrfs: fix transaction abort on set received ioctl due to item overflow 2026-03-03 17:03:59 +01:00
verity.c for-7.0-rc1-tag 2026-02-20 14:57:09 -08:00
verity.h btrfs: add forward declarations and headers, part 1 2024-03-04 16:24:49 +01:00
volumes.c btrfs: avoid taking the device_list_mutex in btrfs_run_dev_stats() 2026-04-07 18:56:05 +02:00
volumes.h btrfs: introduce the device layout aware per-profile available space 2026-04-07 18:55:53 +02:00
xattr.c btrfs: remaining BTRFS_PATH_AUTO_FREE conversions 2025-11-25 01:53:33 +01:00
xattr.h btrfs: update include and forward declarations in headers 2025-03-18 20:35:43 +01:00
zlib.c btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00
zoned.c btrfs: replace kcalloc() calls to kzalloc_objs() 2026-04-07 18:55:59 +02:00
zoned.h btrfs: zoned: factor out the zone loading part into a testable function 2026-02-03 07:59:06 +01:00
zstd.c btrfs: prevent direct reclaim during compressed readahead 2026-04-07 18:56:08 +02:00