[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: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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2 changed files with 17 additions and 14 deletions
30
fs/buffer.c
30
fs/buffer.c
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@ -917,8 +917,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
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* contents - it is a noop if I/O is still in
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* contents - it is a noop if I/O is still in
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* flight on potentially older contents.
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* flight on potentially older contents.
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*/
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*/
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wait_on_buffer(bh);
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ll_rw_block(SWRITE, 1, &bh);
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ll_rw_block(WRITE, 1, &bh);
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brelse(bh);
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brelse(bh);
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spin_lock(lock);
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spin_lock(lock);
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}
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}
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@ -2793,21 +2792,22 @@ int submit_bh(int rw, struct buffer_head * bh)
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/**
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/**
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* ll_rw_block: low-level access to block devices (DEPRECATED)
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* ll_rw_block: low-level access to block devices (DEPRECATED)
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* @rw: whether to %READ or %WRITE or maybe %READA (readahead)
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* @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
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* @nr: number of &struct buffer_heads in the array
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* @nr: number of &struct buffer_heads in the array
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* @bhs: array of pointers to &struct buffer_head
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* @bhs: array of pointers to &struct buffer_head
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*
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*
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* ll_rw_block() takes an array of pointers to &struct buffer_heads,
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* ll_rw_block() takes an array of pointers to &struct buffer_heads, and
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* and requests an I/O operation on them, either a %READ or a %WRITE.
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* requests an I/O operation on them, either a %READ or a %WRITE. The third
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* The third %READA option is described in the documentation for
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* %SWRITE is like %WRITE only we make sure that the *current* data in buffers
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* generic_make_request() which ll_rw_block() calls.
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* are sent to disk. The fourth %READA option is described in the documentation
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* for generic_make_request() which ll_rw_block() calls.
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*
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*
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* This function drops any buffer that it cannot get a lock on (with the
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* This function drops any buffer that it cannot get a lock on (with the
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* BH_Lock state bit), any buffer that appears to be clean when doing a
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* BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
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* write request, and any buffer that appears to be up-to-date when doing
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* clean when doing a write request, and any buffer that appears to be
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* read request. Further it marks as clean buffers that are processed for
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* up-to-date when doing read request. Further it marks as clean buffers that
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* writing (the buffer cache won't assume that they are actually clean until
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* are processed for writing (the buffer cache won't assume that they are
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* the buffer gets unlocked).
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* actually clean until the buffer gets unlocked).
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*
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*
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* ll_rw_block sets b_end_io to simple completion handler that marks
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* ll_rw_block sets b_end_io to simple completion handler that marks
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* the buffer up-to-date (if approriate), unlocks the buffer and wakes
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* the buffer up-to-date (if approriate), unlocks the buffer and wakes
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@ -2823,11 +2823,13 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
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for (i = 0; i < nr; i++) {
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for (i = 0; i < nr; i++) {
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struct buffer_head *bh = bhs[i];
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struct buffer_head *bh = bhs[i];
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if (test_set_buffer_locked(bh))
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if (rw == SWRITE)
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lock_buffer(bh);
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else if (test_set_buffer_locked(bh))
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continue;
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continue;
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get_bh(bh);
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get_bh(bh);
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if (rw == WRITE) {
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if (rw == WRITE || rw == SWRITE) {
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if (test_clear_buffer_dirty(bh)) {
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if (test_clear_buffer_dirty(bh)) {
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bh->b_end_io = end_buffer_write_sync;
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bh->b_end_io = end_buffer_write_sync;
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submit_bh(WRITE, bh);
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submit_bh(WRITE, bh);
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@ -69,6 +69,7 @@ extern int dir_notify_enable;
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#define READ 0
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#define READ 0
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#define WRITE 1
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#define WRITE 1
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#define READA 2 /* read-ahead - don't block if no resources */
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#define READA 2 /* read-ahead - don't block if no resources */
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#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */
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#define SPECIAL 4 /* For non-blockdevice requests in request queue */
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#define SPECIAL 4 /* For non-blockdevice requests in request queue */
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#define READ_SYNC (READ | (1 << BIO_RW_SYNC))
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#define READ_SYNC (READ | (1 << BIO_RW_SYNC))
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#define WRITE_SYNC (WRITE | (1 << BIO_RW_SYNC))
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#define WRITE_SYNC (WRITE | (1 << BIO_RW_SYNC))
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