From: Dan Williams Date: Fri, 27 Jun 2008 22:31:50 +0000 (+1000) Subject: md: kill STRIPE_OP_MOD_DMA in raid5 offload X-Git-Tag: v2.6.27-rc1~957^2~39 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b203886edbcaac3ca427cf4dbcb50b18bdb346fd;p=linux-2.6 md: kill STRIPE_OP_MOD_DMA in raid5 offload From: Dan Williams This micro-optimization allowed the raid code to skip a re-read of the parity block after checking parity. It took advantage of the fact that xor-offload-engines have their own internal result buffer and can check parity without writing to memory. Remove it for the following reasons: 1/ It is a layering violation for MD to need to manage the DMA and non-DMA paths within async_xor_zero_sum 2/ Bad precedent to toggle the 'ops' flags outside the lock 3/ Hard to realize a performance gain as reads will not need an updated parity block and writes will dirty it anyways. Signed-off-by: Dan Williams Signed-off-by: Neil Brown --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 8c4e6149da..60e61d2464 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -837,15 +837,10 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx, static void ops_complete_check(void *stripe_head_ref) { struct stripe_head *sh = stripe_head_ref; - int pd_idx = sh->pd_idx; pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector); - if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) && - sh->ops.zero_sum_result == 0) - set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags); - set_bit(STRIPE_OP_CHECK, &sh->ops.complete); set_bit(STRIPE_HANDLE, &sh->state); release_stripe(sh); @@ -873,11 +868,6 @@ static void ops_run_check(struct stripe_head *sh) tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &sh->ops.zero_sum_result, 0, NULL, NULL, NULL); - if (tx) - set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending); - else - clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending); - atomic_inc(&sh->count); tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx, ops_complete_check, sh); diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h index f0827d31ae..4ecae31a3d 100644 --- a/include/linux/raid/raid5.h +++ b/include/linux/raid/raid5.h @@ -267,10 +267,8 @@ struct r6_state { /* modifiers to the base operations * STRIPE_OP_MOD_REPAIR_PD - compute the parity block and write it back - * STRIPE_OP_MOD_DMA_CHECK - parity is not corrupted by the check */ #define STRIPE_OP_MOD_REPAIR_PD 7 -#define STRIPE_OP_MOD_DMA_CHECK 8 /* * Plugging: