writeback: enforce s_umount locking in writeback_inodes_sb
Make sure that not only sync_filesystem but all callers of writeback_inodes_sb
have the superblock protected against remount. As-is this disables all
functionality for these callers, but the next patch relies on this locking to
fix writeback_inodes_sb for sync_filesystem.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 7596669..2627f0d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1180,6 +1180,8 @@
.sync_mode = WB_SYNC_NONE,
};
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
args.nr_pages = nr_dirty + nr_unstable +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
@@ -1197,7 +1199,9 @@
int writeback_inodes_sb_if_idle(struct super_block *sb)
{
if (!writeback_in_progress(sb->s_bdi)) {
+ down_read(&sb->s_umount);
writeback_inodes_sb(sb);
+ up_read(&sb->s_umount);
return 1;
} else
return 0;
@@ -1220,6 +1224,8 @@
.range_cyclic = 0,
};
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
bdi_queue_work_onstack(&args);
wait_sb_inodes(sb);
}