From: Jan Kara 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: Jan Kara Signed-off-by: Andrew Morton --- fs/buffer.c | 30 ++++++++++++++++-------------- include/linux/fs.h | 1 + 2 files changed, 17 insertions(+), 14 deletions(-) diff -puN fs/buffer.c~make-ll_rw_block-wait-for-buffer-lock fs/buffer.c --- 25/fs/buffer.c~make-ll_rw_block-wait-for-buffer-lock Mon Jul 11 16:31:50 2005 +++ 25-akpm/fs/buffer.c Mon Jul 11 16:31:50 2005 @@ -917,8 +917,7 @@ static int fsync_buffers_list(spinlock_t * 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 /** * 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 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); diff -puN include/linux/fs.h~make-ll_rw_block-wait-for-buffer-lock include/linux/fs.h --- 25/include/linux/fs.h~make-ll_rw_block-wait-for-buffer-lock Mon Jul 11 16:31:50 2005 +++ 25-akpm/include/linux/fs.h Mon Jul 11 16:31:50 2005 @@ -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)) _