FAILED: patch "[PATCH] f2fs: fix to use bio_in_atomic() in f2fs_write_end_io()" failed to apply to 7.3-stable tree

The patch below does not apply to the 7.3-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.3.y
git checkout FETCH_HEAD
git cherry-pick -x e4582e5f3b439228d4e900edcf8225aa89be32b4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '[email protected]' --subject-prefix 'PATCH 7.3.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From e4582e5f3b439228d4e900edcf8225aa89be32b4 Mon Sep 17 00:00:00 2001
From: Chao Yu <[email protected]>
Date: Sat, 10 Oct 2026 14:55:45 +0800
Subject: [PATCH] f2fs: fix to use bio_in_atomic() in f2fs_write_end_io()

f2fs_write_end_io() uses in_atomic() to decide whether a write bio which exceeds max_atc_write_bio_size or max_atc_write_bio_entry_cnt should be completed in sbi->wq rather than in the current context.

However, in_atomic() is not meant to be used outside core kernel code (checkpatch.pl warns about it), as it only looks at preempt_count(): it misses irqs-disabled and RCU read-side critical sections, and on kernels without CONFIG_PREEMPT_COUNT it cannot see spinlock-held sections at all. In those contexts, a large write bio will still be completed inline, which defeats the purpose of the above knobs.

The block layer provides bio_in_atomic() for exactly this purpose, it checks rcu_preempt_depth() and preemptible(), and conservatively returns true if CONFIG_PREEMPT_COUNT is disabled, let's use it instead. The difference is as below:

Context | in_atomic() | bio_in_atomic()
-------------------------------------+----------------+----------------

 Hard IRQ / softirq                   | true           | true
 IRQs disabled, preempt count 0       | false (missed) | true
 RCU read lock (CONFIG_PREEMPTION)    | false (missed) | true
 Kernel w/o CONFIG_PREEMPT_COUNT      | IRQ ctx only   | always true

Note that on kernels without CONFIG_PREEMPT_COUNT, write bios exceeding the thresholds will always be offloaded to sbi->wq, since there is no way to tell whether the current context is atomic. The thresholds default to UINT_MAX, so the default behavior is not changed.

---
 fs/f2fs/data.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

index 1925fc3aef57b..ae3bde0767f3c 100644
@@ -398,8 +398,9 @@ static void f2fs_write_end_io(struct bio *bio)
 
 	sbi = bio->bi_private;
 
-	if (in_atomic() && (bio->bi_iter.bi_size > sbi->max_atc_write_bio_size ||
-			F2FS_BIO(bio)->entry_cnt > sbi->max_atc_write_bio_entry_cnt)) {
+	if (bio_in_atomic() &&
+	    (bio->bi_iter.bi_size > sbi->max_atc_write_bio_size ||
+	     F2FS_BIO(bio)->entry_cnt > sbi->max_atc_write_bio_entry_cnt)) {
 		struct work_struct *w;
 
 		w = &container_of(bio, struct f2fs_bio, bio)->work;

2.53.0

From: Chao Yu <[email protected]>

[ Upstream commit e4582e5f3b439228d4e900edcf8225aa89be32b4 ]

f2fs_write_end_io() uses in_atomic() to decide whether a write bio which exceeds max_atc_write_bio_size or max_atc_write_bio_entry_cnt should be completed in sbi->wq rather than in the current context.

However, in_atomic() is not meant to be used outside core kernel code (checkpatch.pl warns about it), as it only looks at preempt_count(): it misses irqs-disabled and RCU read-side critical sections, and on kernels without CONFIG_PREEMPT_COUNT it cannot see spinlock-held sections at all. In those contexts, a large write bio will still be completed inline, which defeats the purpose of the above knobs.

The block layer provides bio_in_atomic() for exactly this purpose, it checks rcu_preempt_depth() and preemptible(), and conservatively returns true if CONFIG_PREEMPT_COUNT is disabled, let's use it instead. The difference is as below:

Context | in_atomic() | bio_in_atomic()
-------------------------------------+----------------+----------------

 Hard IRQ / softirq                   | true           | true
 IRQs disabled, preempt count 0       | false (missed) | true
 RCU read lock (CONFIG_PREEMPTION)    | false (missed) | true
 Kernel w/o CONFIG_PREEMPT_COUNT      | IRQ ctx only   | always true

Note that on kernels without CONFIG_PREEMPT_COUNT, write bios exceeding the thresholds will always be offloaded to sbi->wq, since there is no way to tell whether the current context is atomic. The thresholds default to UINT_MAX, so the default behavior is not changed.

---
 fs/f2fs/data.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index cfd81bfc28a22..43e623a0bd30a 100644
@@ -399,7 +399,8 @@ static void f2fs_write_end_io(struct bio *bio)
 
 	sbi = bio->bi_private;
 
-	if (in_atomic() && bio->bi_iter.bi_size > sbi->max_atc_write_bio_size) {
+	if (bio_in_atomic() &&
+	    bio->bi_iter.bi_size > sbi->max_atc_write_bio_size) {
 		struct work_struct *w;
 
 		w = &container_of(bio, struct f2fs_bio, bio)->work;

2.53.0