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Kuan-Wei Chiu 237213776d ubifs: remove unnecessary cond_resched() from list_sort() compare 
Patch series "lib/list_sort: Clean up list_sort() scheduling workarounds",
v3.

Historically, list_sort() included a hack in merge_final() that
periodically invoked dummy cmp(priv, b, b) calls when merging highly
unbalanced lists.  This allowed the caller to invoke cond_resched() within
their comparison callbacks to avoid soft lockups.  

However, an audit of the kernel tree shows that fs/ubifs/ has been the
sole user of this mechanism.  For all other generic list_sort() users,
this results in wasted function calls and unnecessary overhead in a tight
loop.

Recent discussions and code inspection confirmed that the lists being
sorted in UBIFS are bounded in size (a few thousand elements at most), and
the comparison functions are extremely lightweight.  Therefore, UBIFS does
not actually need to rely on this mechanism.


This patch (of 2):

Historically, UBIFS embedded cond_resched() calls inside its list_sort()
comparison callbacks (data_nodes_cmp, nondata_nodes_cmp, and
replay_entries_cmp) to prevent soft lockups when sorting long lists.

However, further inspection by Richard Weinberger reveals that these
compare functions are extremely lightweight and do not perform any
blocking MTD I/O. Furthermore, the lists being sorted are strictly
bounded in size:
- In the GC case, the list contains at most the number of nodes that
  fit into a single LEB.
- In the replay case, the list spans across a few LEBs from the UBIFS
  journal, amounting to at most a few thousand elements.

Since the compare functions are called a few thousand times at most, the
overhead of frequent scheduling points is unjustified.  Removing the
cond_resched() calls simplifies the comparison logic and reduces
unnecessary context switch checks during the sort.

Link: https://lkml.kernel.org/r/20260320180938.1827148-1-visitorckw@gmail.com
Link: https://lkml.kernel.org/r/20260320180938.1827148-2-visitorckw@gmail.com
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Acked-by: Richard Weinberger <richard@nod.at>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mars Cheng <marscheng@google.com>
Cc: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 		2026-04-02 23:36:22 -07:00
..
9p Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
adfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
affs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
afs rxrpc, afs: Fix missing error pointer check after rxrpc_kernel_lookup_peer() 2026-03-06 17:49:52 -08:00
autofs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
befs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
bfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
btrfs btrfs: use xor_gen 2026-04-02 23:36:21 -07:00
cachefiles Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
ceph ceph: do not skip the first folio of the next object in writeback 2026-03-09 12:34:40 +01:00
coda Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
configfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
cramfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
crypto Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
debugfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
devpts Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
dlm Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ecryptfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
efivarfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
efs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
erofs erofs: fix interlaced plain identification for encoded extents 2026-02-25 17:40:58 +08:00
exfat Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
exportfs fs: add helpers name_is_dot{,dot,_dotdot} 2026-01-29 10:06:59 +01:00
ext2 Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
ext4 Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
f2fs fsverity fixes for v7.0-rc1 2026-02-22 13:12:04 -08:00
fat Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
freevxfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
fuse Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
gfs2 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
hfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
hfsplus Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
hostfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
hpfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
hugetlbfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
iomap iomap: reject delalloc mappings during writeback 2026-03-04 14:31:56 +01:00
isofs Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
jbd2 Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
jffs2 Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
jfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
lockd Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
minix vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
netfs netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence 2026-02-26 14:44:32 +01:00
nfs NFS: Fix NFS KConfig typos 2026-02-27 15:42:14 -05:00
nfs_common
…
nfsd nfsd-7.0 fixes: 2026-03-18 14:27:11 -07:00
nilfs2 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
nls
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notify Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ntfs3 treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
ocfs2 ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison 2026-03-27 21:19:49 -07:00
omfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
openpromfs
…
orangefs Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
overlayfs Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
proc proc: array: drop stale FIXME about RCU in task_sig() 2026-03-27 21:19:32 -07:00
pstore Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
qnx4 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
qnx6 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
quota Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ramfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
resctrl Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
romfs mm.git review status for linus..mm-stable 2026-02-18 20:50:32 -08:00
smb three client fixes 2026-03-20 09:07:29 -07:00
squashfs Squashfs: check metadata block offset is within range 2026-02-24 11:13:27 -08:00
sysfs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
tests fs/tests: exec: Remove bad test vector 2026-03-18 11:41:53 -07:00
tracefs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ubifs ubifs: remove unnecessary cond_resched() from list_sort() compare 2026-04-02 23:36:22 -07:00
udf Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
ufs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
unicode Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
vboxsf Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
verity fsverity: add dependency on 64K or smaller pages 2026-03-02 21:05:34 -08:00
xfs xfs: fix integer overflow in bmap intent sort comparator 2026-03-11 13:21:42 +01:00
zonefs Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
Kconfig
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Kconfig.binfmt
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Makefile vfs-7.0-rc1.nullfs 2026-02-09 13:41:34 -08:00
aio.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
anon_inodes.c
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attr.c fs,fsverity: reject size changes on fsverity files in setattr_prepare 2026-01-29 09:39:41 -08:00
backing-file.c
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bad_inode.c
…
binfmt_elf.c rseq: slice ext: Ensure rseq feature size differs from original rseq size 2026-02-23 11:19:19 +01:00
binfmt_elf_fdpic.c binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4 2026-02-23 16:09:00 -08:00
binfmt_flat.c
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binfmt_misc.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
binfmt_script.c
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bpf_fs_kfuncs.c
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buffer.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
char_dev.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
compat_binfmt_elf.c
…
coredump.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
d_path.c
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dax.c
…
dcache.c vfs-7.0-rc1.misc.2 2026-02-16 13:00:36 -08:00
direct-io.c
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drop_caches.c
…
eventfd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
eventpoll.c vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
exec.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
fcntl.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
fhandle.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
file.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
file_attr.c vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
file_table.c Changes since last update: 2026-02-09 16:08:40 -08:00
filesystems.c sysfs(2): fs_index() argument is _not_ a pathname 2026-01-16 12:52:04 -05:00
fs-writeback.c vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
fs_context.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
fs_dirent.c
…
fs_parser.c
…
fs_pin.c
…
fs_struct.c fs: add <linux/init_task.h> for 'init_fs' 2026-01-14 16:50:37 +01:00
fserror.c
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fsopen.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
init.c struct filename series 2026-02-09 16:58:28 -08:00
inode.c fsverity updates for 7.0 2026-02-12 10:41:34 -08:00
internal.h struct filename series 2026-02-09 16:58:28 -08:00
ioctl.c
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kernel_read_file.c
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libfs.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
locks.c NFSD 7.0 Release Notes 2026-02-12 08:23:53 -08:00
mbcache.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
mnt_idmapping.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
mount.h
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mpage.c
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namei.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
namespace.c vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
nsfs.c nsfs: tighten permission checks for handle opening 2026-02-27 22:00:11 +01:00
nullfs.c
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open.c struct filename series 2026-02-09 16:58:28 -08:00
pidfs.c vfs-7.0-rc2.fixes 2026-02-25 10:34:23 -08:00
pipe.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
pnode.c
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pnode.h
…
posix_acl.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
proc_namespace.c
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read_write.c
…
readdir.c
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remap_range.c
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select.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
seq_file.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
signalfd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
splice.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
stack.c
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stat.c statx: switch to CLASS(filename_maybe_null) 2026-01-16 12:52:04 -05:00
statfs.c user_statfs(): switch to CLASS(filename) 2026-01-16 12:52:04 -05:00
super.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
sync.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
sysctls.c
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timerfd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
userfaultfd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
utimes.c do_utimes_path(): switch to CLASS(filename_uflags) 2026-01-16 12:52:03 -05:00
xattr.c filename_...xattr(): don't consume filename reference 2026-01-16 12:52:03 -05:00