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Btrfs: protect conditions within root->log_mutex while waiting

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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>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Liu Bo 2017-09-01 16:14:30 -06:00 committed by David Sterba
parent 45bac0f3d2
commit 49e83f5735
1 changed files with 17 additions and 15 deletions
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32
fs/btrfs/tree-log.c
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@ -2699,34 +2699,36 @@ 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);
if (!(root->log_transid_committed < transid &&
atomic_read(&root->log_commit[index])))
break;
mutex_unlock(&root->log_mutex);
if (root->log_transid_committed < transid &&
atomic_read(&root->log_commit[index]))
schedule();
finish_wait(&root->log_commit_wait[index], &wait);
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,