From 8d49bf3f9d4f6d61f0f759f75e79caaee6dcc6e4 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Mon, 10 Feb 2003 00:29:41 -0800 Subject: [PATCH] Fix synchronous writers to wait properly for the result Mikulas Patocka points out a bug in ll_rw_block() usage. Typical usage is: mark_buffer_dirty(bh); ll_rw_block(WRITE, 1, &bh); wait_on_buffer(bh); the problem is that if the buffer was locked on entry to this code sequence (due to in-progress I/O), ll_rw_block() will not wait, and start new I/O. So this code will wait on the _old_ I/O, and will then continue execution, leaving the buffer dirty. It turns out that all callers were only writing one buffer, and they were all waiting on that writeout. So I added a new sync_dirty_buffer() function: void sync_dirty_buffer(struct buffer_head *bh) { lock_buffer(bh); if (test_clear_buffer_dirty(bh)) { get_bh(bh); bh->b_end_io = end_buffer_io_sync; submit_bh(WRITE, bh); } else { unlock_buffer(bh); } } which allowed a fair amount of code to be removed, while adding the desired data-integrity guarantees. UFS has its own wrappers around ll_rw_block() which got in the way, so this operation was open-coded in that case. --- include/linux/buffer_head.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/buffer_head.h') diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index aaefe4e964b7..8def67e47d28 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -169,6 +169,7 @@ struct buffer_head *alloc_buffer_head(void); void free_buffer_head(struct buffer_head * bh); void FASTCALL(unlock_buffer(struct buffer_head *bh)); void ll_rw_block(int, int, struct buffer_head * bh[]); +void sync_dirty_buffer(struct buffer_head *bh); int submit_bh(int, struct buffer_head *); void write_boundary_block(struct block_device *bdev, sector_t bblock, unsigned blocksize); -- cgit v1.2.3