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Commit a7662236 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
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[PATCH] Make ll_rw_block() wait for buffer lock 



Introduce new ll_rw_block() operation SWRITE meaning that block layer should
wait for the buffer lock and write-out afterwards.  Hence data in buffers at
the time of call are guaranteed to be submitted to the disk.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e6c9f5c1

fs/buffer.c

+16 −14
Original line number Diff line number Diff line
@@ -917,8 +917,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) 
				 * contents - it is a noop if I/O is still in

				 * flight on potentially older contents.

				 */

				wait_on_buffer(bh);

				ll_rw_block(WRITE, 1, &bh);

				ll_rw_block(SWRITE, 1, &bh);

				brelse(bh);

				spin_lock(lock);

			}
@@ -2793,21 +2792,22 @@ int submit_bh(int rw, struct buffer_head * bh) 


/**

 * ll_rw_block: low-level access to block devices (DEPRECATED)

 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)

 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)

 * @nr: number of &struct buffer_heads in the array

 * @bhs: array of pointers to &struct buffer_head

 *

 * ll_rw_block() takes an array of pointers to &struct buffer_heads,

 * and requests an I/O operation on them, either a %READ or a %WRITE.

 * The third %READA option is described in the documentation for

 * generic_make_request() which ll_rw_block() calls.

 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and

 * requests an I/O operation on them, either a %READ or a %WRITE.  The third

 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers

 * are sent to disk. The fourth %READA option is described in the documentation

 * for generic_make_request() which ll_rw_block() calls.

 *

 * This function drops any buffer that it cannot get a lock on (with the

 * BH_Lock state bit), any buffer that appears to be clean when doing a

 * write request, and any buffer that appears to be up-to-date when doing

 * read request.  Further it marks as clean buffers that are processed for

 * writing (the buffer cache won't assume that they are actually clean until

 * the buffer gets unlocked).

 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be

 * clean when doing a write request, and any buffer that appears to be

 * up-to-date when doing read request.  Further it marks as clean buffers that

 * are processed for writing (the buffer cache won't assume that they are

 * actually clean until the buffer gets unlocked).

 *

 * ll_rw_block sets b_end_io to simple completion handler that marks

 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
@@ -2823,11 +2823,13 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) 
	for (i = 0; i < nr; i++) {

		struct buffer_head *bh = bhs[i];



		if (test_set_buffer_locked(bh))

		if (rw == SWRITE)

			lock_buffer(bh);

		else if (test_set_buffer_locked(bh))

			continue;



		get_bh(bh);

		if (rw == WRITE) {

		if (rw == WRITE || rw == SWRITE) {

			if (test_clear_buffer_dirty(bh)) {

				bh->b_end_io = end_buffer_write_sync;

				submit_bh(WRITE, bh);

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ extern int dir_notify_enable; 
#define READ 0

#define WRITE 1

#define READA 2		/* read-ahead  - don't block if no resources */

#define SWRITE 3	/* for ll_rw_block() - wait for buffer lock */

#define SPECIAL 4	/* For non-blockdevice requests in request queue */

#define READ_SYNC	(READ | (1 << BIO_RW_SYNC))

#define WRITE_SYNC	(WRITE | (1 << BIO_RW_SYNC))