* [PATCH] Btrfs: protect conditions within root->log_mutex while waiting
@ 2017-09-01 22:14 Liu Bo
2017-09-06 13:50 ` David Sterba
0 siblings, 1 reply; 2+ messages in thread
From: Liu Bo @ 2017-09-01 22:14 UTC (permalink / raw)
To: linux-btrfs
Both wait_for_commit() and wait_for_writer() are checking the
condition out of the mutex lock.
This refactors code a bit to be lock safe.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
fs/btrfs/tree-log.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 3a11ae6..434dcd5 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2701,34 +2701,36 @@ static void wait_log_commit(struct btrfs_root *root, int transid)
* so we know that if ours is more than 2 older than the
* current transaction, we're done
*/
- do {
+ for (;;) {
prepare_to_wait(&root->log_commit_wait[index],
&wait, TASK_UNINTERRUPTIBLE);
- mutex_unlock(&root->log_mutex);
- if (root->log_transid_committed < transid &&
- atomic_read(&root->log_commit[index]))
- schedule();
+ if (!(root->log_transid_committed < transid &&
+ atomic_read(&root->log_commit[index])))
+ break;
- finish_wait(&root->log_commit_wait[index], &wait);
+ mutex_unlock(&root->log_mutex);
+ schedule();
mutex_lock(&root->log_mutex);
- } while (root->log_transid_committed < transid &&
- atomic_read(&root->log_commit[index]));
+ }
+ finish_wait(&root->log_commit_wait[index], &wait);
}
static void wait_for_writer(struct btrfs_root *root)
{
DEFINE_WAIT(wait);
- while (atomic_read(&root->log_writers)) {
- prepare_to_wait(&root->log_writer_wait,
- &wait, TASK_UNINTERRUPTIBLE);
+ for (;;) {
+ prepare_to_wait(&root->log_writer_wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (!atomic_read(&root->log_writers))
+ break;
+
mutex_unlock(&root->log_mutex);
- if (atomic_read(&root->log_writers))
- schedule();
- finish_wait(&root->log_writer_wait, &wait);
+ schedule();
mutex_lock(&root->log_mutex);
}
+ finish_wait(&root->log_writer_wait, &wait);
}
static inline void btrfs_remove_log_ctx(struct btrfs_root *root,
--
2.9.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] Btrfs: protect conditions within root->log_mutex while waiting
2017-09-01 22:14 [PATCH] Btrfs: protect conditions within root->log_mutex while waiting Liu Bo
@ 2017-09-06 13:50 ` David Sterba
0 siblings, 0 replies; 2+ messages in thread
From: David Sterba @ 2017-09-06 13:50 UTC (permalink / raw)
To: Liu Bo; +Cc: linux-btrfs
On Fri, Sep 01, 2017 at 04:14:30PM -0600, Liu Bo wrote:
> Both wait_for_commit() and wait_for_writer() are checking the
> condition out of the mutex lock.
>
> This refactors code a bit to be lock safe.
>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-09-06 13:50 ` David Sterba
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