From 3c9ad9bd87b03032999ddbeb44bdf7938f7dbd57 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Fri, 27 Jul 2012 15:08:09 +0100 Subject: [PATCH] dm persistent data: stop using dm_bm_unlock_move when shadowing blocks in tm Stop using dm_bm_unlock_move when shadowing blocks in the transaction manager as an optimisation and remove the function as it is then no longer used. Some code, such as the space maps, keeps using on-disk data structures from the previous transaction. It can do this because blocks won't be reallocated until the subsequent transaction. Using dm_bm_unlock_move to copy blocks sounds like a win, but it forces a synchronous read should the old block be accessed. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/persistent-data/dm-block-manager.c | 16 ---------------- drivers/md/persistent-data/dm-block-manager.h | 8 -------- drivers/md/persistent-data/dm-transaction-manager.c | 17 ++++++++++++++--- 3 files changed, 14 insertions(+), 27 deletions(-) diff --git a/drivers/md/persistent-data/dm-block-manager.c b/drivers/md/persistent-data/dm-block-manager.c index 4b5c504..ad1712e 100644 --- a/drivers/md/persistent-data/dm-block-manager.c +++ b/drivers/md/persistent-data/dm-block-manager.c @@ -584,22 +584,6 @@ int dm_bm_unlock(struct dm_block *b) } EXPORT_SYMBOL_GPL(dm_bm_unlock); -int dm_bm_unlock_move(struct dm_block *b, dm_block_t n) -{ - struct buffer_aux *aux; - - aux = dm_bufio_get_aux_data(to_buffer(b)); - - if (aux->write_locked) { - dm_bufio_mark_buffer_dirty(to_buffer(b)); - bl_up_write(&aux->lock); - } else - bl_up_read(&aux->lock); - - dm_bufio_release_move(to_buffer(b), n); - return 0; -} - int dm_bm_flush_and_unlock(struct dm_block_manager *bm, struct dm_block *superblock) { diff --git a/drivers/md/persistent-data/dm-block-manager.h b/drivers/md/persistent-data/dm-block-manager.h index 924833d..3278855 100644 --- a/drivers/md/persistent-data/dm-block-manager.h +++ b/drivers/md/persistent-data/dm-block-manager.h @@ -97,14 +97,6 @@ int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b, int dm_bm_unlock(struct dm_block *b); /* - * An optimisation; we often want to copy a block's contents to a new - * block. eg, as part of the shadowing operation. It's far better for - * bufio to do this move behind the scenes than hold 2 locks and memcpy the - * data. - */ -int dm_bm_unlock_move(struct dm_block *b, dm_block_t n); - -/* * It's a common idiom to have a superblock that should be committed last. * * @superblock should be write-locked on entry. It will be unlocked during diff --git a/drivers/md/persistent-data/dm-transaction-manager.c b/drivers/md/persistent-data/dm-transaction-manager.c index b4f0583..d247a35 100644 --- a/drivers/md/persistent-data/dm-transaction-manager.c +++ b/drivers/md/persistent-data/dm-transaction-manager.c @@ -219,13 +219,24 @@ static int __shadow_block(struct dm_transaction_manager *tm, dm_block_t orig, if (r < 0) return r; - r = dm_bm_unlock_move(orig_block, new); - if (r < 0) { + /* + * It would be tempting to use dm_bm_unlock_move here, but some + * code, such as the space maps, keeps using the old data structures + * secure in the knowledge they won't be changed until the next + * transaction. Using unlock_move would force a synchronous read + * since the old block would no longer be in the cache. + */ + r = dm_bm_write_lock_zero(tm->bm, new, v, result); + if (r) { dm_bm_unlock(orig_block); return r; } - return dm_bm_write_lock(tm->bm, new, v, result); + memcpy(dm_block_data(*result), dm_block_data(orig_block), + dm_bm_block_size(tm->bm)); + + dm_bm_unlock(orig_block); + return r; } int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig, -- 2.7.4