gc_thread_func() tests gc_th->gc_wake and then clears it with
separate plain accesses. sysfs gc_urgent writes set the same flag and
wake the GC thread. If a sysfs writer stores true between the GC
thread's load and store, the later store false can clear the new wake
request.
Store gc_wake as an atomic_t. Use atomic_read() for the wait
condition, atomic_xchg(..., 0) in the GC thread, and atomic_set(..., 1)
in the sysfs trigger paths. This makes the consume-and-clear operation
atomic with respect to new wake requests: a set before the exchange is
consumed by the current iteration, while a set after the exchange stays
pending for the next wait.
Fixes: d9872a698c39 ("f2fs: introduce gc_urgent mode for background GC")
Signed-off-by: Ziyu Zhang <[email protected]>
---
fs/f2fs/gc.c | 7 +++----
fs/f2fs/gc.h | 2 +-
fs/f2fs/sysfs.c | 4 ++--
3 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 098e9f71421e..71e40e4083ad 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -49,15 +49,14 @@ static int gc_thread_func(void *data)
wait_event_freezable_timeout(*wq,
kthread_should_stop() ||
waitqueue_active(fggc_wq) ||
- gc_th->gc_wake,
+ atomic_read(&gc_th->gc_wake),
msecs_to_jiffies(wait_ms));
if (test_opt(sbi, GC_MERGE) && waitqueue_active(fggc_wq))
foreground = true;
/* give it a try one time */
- if (gc_th->gc_wake)
- gc_th->gc_wake = false;
+ atomic_xchg(&gc_th->gc_wake, 0);
if (f2fs_readonly(sbi->sb)) {
stat_other_skip_bggc_count(sbi);
@@ -214,7 +213,7 @@ int f2fs_start_gc_thread(struct f2fs_sb_info *sbi)
gc_th->boost_zoned_gc_percent = 0;
}
- gc_th->gc_wake = false;
+ atomic_set(&gc_th->gc_wake, 0);
sbi->gc_thread = gc_th;
init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index 24e8b1c27acc..65e5b062a0d3 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -56,7 +56,7 @@ struct f2fs_gc_kthread {
unsigned int no_gc_sleep_time;
/* for changing gc mode */
- bool gc_wake;
+ atomic_t gc_wake;
/* for GC_MERGE mount option */
wait_queue_head_t fggc_wq; /*
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index f736052dea50..6ca5943450d5 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -586,7 +586,7 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
} else if (t == 1) {
sbi->gc_mode = GC_URGENT_HIGH;
if (sbi->gc_thread) {
- sbi->gc_thread->gc_wake = true;
+ atomic_set(&sbi->gc_thread->gc_wake, 1);
wake_up_interruptible_all(
&sbi->gc_thread->gc_wait_queue_head);
wake_up_discard_thread(sbi, true);
@@ -596,7 +596,7 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
} else if (t == 3) {
sbi->gc_mode = GC_URGENT_MID;
if (sbi->gc_thread) {
- sbi->gc_thread->gc_wake = true;
+ atomic_set(&sbi->gc_thread->gc_wake, 1);
wake_up_interruptible_all(
&sbi->gc_thread->gc_wait_queue_head);
}
--
2.43.0
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