From f44cc269a1c148ad83332d85fe54607e8874ca79 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Sat, 22 Jun 2024 20:52:39 -0400
Subject: [PATCH] bcachefs: fix seqmutex_relock()
We were grabbing the sequence number before unlock incremented it - fix
this by moving the increment to seqmutex_lock() (so the seqmutex_relock()
failure path skips the mutex_trylock()), and returning the sequence
number from unlock(), to make the API simpler and safer.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/bcachefs/debug.c | 8 ++------
fs/bcachefs/seqmutex.h | 11 ++++-------
2 files changed, 6 insertions(+), 13 deletions(-)
diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index 51cbf39283612..8ec2d44e4956e 100644
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -575,7 +575,6 @@ static ssize_t bch2_btree_transactions_read(struct file *file, char __user *buf,
struct bch_fs *c = i->c;
struct btree_trans *trans;
ssize_t ret = 0;
- u32 seq;
i->ubuf = buf;
i->size = size;
@@ -589,8 +588,7 @@ static ssize_t bch2_btree_transactions_read(struct file *file, char __user *buf,
continue;
closure_get(&trans->ref);
- seq = seqmutex_seq(&c->btree_trans_lock);
- seqmutex_unlock(&c->btree_trans_lock);
+ u32 seq = seqmutex_unlock(&c->btree_trans_lock);
ret = flush_buf(i);
if (ret) {
@@ -811,7 +809,6 @@ static ssize_t bch2_btree_deadlock_read(struct file *file, char __user *buf,
struct bch_fs *c = i->c;
struct btree_trans *trans;
ssize_t ret = 0;
- u32 seq;
i->ubuf = buf;
i->size = size;
@@ -828,8 +825,7 @@ static ssize_t bch2_btree_deadlock_read(struct file *file, char __user *buf,
continue;
closure_get(&trans->ref);
- seq = seqmutex_seq(&c->btree_trans_lock);
- seqmutex_unlock(&c->btree_trans_lock);
+ u32 seq = seqmutex_unlock(&c->btree_trans_lock);
ret = flush_buf(i);
if (ret) {
diff --git a/fs/bcachefs/seqmutex.h b/fs/bcachefs/seqmutex.h
index c1860d8163fb1..c4b3d8d3f4149 100644
--- a/fs/bcachefs/seqmutex.h
+++ b/fs/bcachefs/seqmutex.h
@@ -19,17 +19,14 @@ static inline bool seqmutex_trylock(struct seqmutex *lock)
static inline void seqmutex_lock(struct seqmutex *lock)
{
mutex_lock(&lock->lock);
-}
-
-static inline void seqmutex_unlock(struct seqmutex *lock)
-{
lock->seq++;
- mutex_unlock(&lock->lock);
}
-static inline u32 seqmutex_seq(struct seqmutex *lock)
+static inline u32 seqmutex_unlock(struct seqmutex *lock)
{
- return lock->seq;
+ u32 seq = lock->seq;
+ mutex_unlock(&lock->lock);
+ return seq;
}
static inline bool seqmutex_relock(struct seqmutex *lock, u32 seq)
--
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