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Commit 49e83f57 authored by Liu Bo's avatar Liu Bo Committed by David Sterba
Browse files

Btrfs: protect conditions within root->log_mutex while waiting 



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: default avatarLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 45bac0f3

fs/btrfs/tree-log.c

+16 −14
Original line number Diff line number Diff line
@@ -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);

		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);

		mutex_lock(&root->log_mutex);

	}

	finish_wait(&root->log_writer_wait, &wait);

}



static inline void btrfs_remove_log_ctx(struct btrfs_root *root,