From: Chris Mason <mason@suse.com>
Hmpf, one more. If one proc does a wait_on_buffer while another does
discard_buffer, bh->b_bdev might be null by the time __wait_on_buffer uses
it.
Someone hit this with reiserfs, but it should be possible to trigger
anywhere.
---
25-akpm/fs/buffer.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletion(-)
diff -puN fs/buffer.c~per-backing_dev-unplugging-fix-42 fs/buffer.c
--- 25/fs/buffer.c~per-backing_dev-unplugging-fix-42 Mon Mar 15 14:13:44 2004
+++ 25-akpm/fs/buffer.c Mon Mar 15 14:13:44 2004
@@ -132,7 +132,11 @@ void __wait_on_buffer(struct buffer_head
do {
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
if (buffer_locked(bh)) {
- blk_run_address_space(bh->b_bdev->bd_inode->i_mapping);
+ struct block_device *bd;
+ smp_mb();
+ bd = bh->b_bdev;
+ if (bd)
+ blk_run_address_space(bd->bd_inode->i_mapping);
io_schedule();
}
} while (buffer_locked(bh));
_