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bcachefs: Fix lifetime issue in device iterator helpers

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bch2_get_next_dev() and bch2_get_next_online_dev() iterate over devices,
dropping and taking refs as they go; we can't access the previous device
(for ca->dev_idx) after we've dropped our ref to it, unless we take
rcu_read_lock() first.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-05-04 12:55:44 -04:00
parent 3a2d025927
commit 18b4abcead
1 changed files with 2 additions and 2 deletions
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4
fs/bcachefs/sb-members.h
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@ -107,10 +107,10 @@ static inline struct bch_dev *__bch2_next_dev(struct bch_fs *c, struct bch_dev *
static inline struct bch_dev *bch2_get_next_dev(struct bch_fs *c, struct bch_dev *ca)
{
rcu_read_lock();
if (ca)
percpu_ref_put(&ca->ref);
rcu_read_lock();
if ((ca = __bch2_next_dev(c, ca, NULL)))
percpu_ref_get(&ca->ref);
rcu_read_unlock();
@ -132,10 +132,10 @@ static inline struct bch_dev *bch2_get_next_online_dev(struct bch_fs *c,
struct bch_dev *ca,
unsigned state_mask)
{
rcu_read_lock();
if (ca)
percpu_ref_put(&ca->io_ref);
rcu_read_lock();
while ((ca = __bch2_next_dev(c, ca, NULL)) &&
(!((1 << ca->mi.state) & state_mask) ||
!percpu_ref_tryget(&ca->io_ref)))