md: replace R5_WantPrexor with R5_WantDrain, add 'prexor' reconstruct_states

From: Dan Williams <dan.j.williams@intel.com>

Currently ops_run_biodrain and other locations have extra logic to determine
which blocks are processed in the prexor and non-prexor cases.  This can be
eliminated if handle_write_operations5 flags the blocks to be processed in all
cases via R5_Wantdrain.  The presence of the prexor operation is tracked in
sh->reconstruct_state.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>

1 files changed, 29 insertions, 60 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b9159367491a..c71246061c0e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -637,7 +637,7 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
         for (i = disks; i--; ) {
                 struct r5dev *dev = &sh->dev[i];
                 /* Only process blocks that are known to be uptodate */
-                if (dev->towrite && test_bit(R5_Wantprexor, &dev->flags))
+                if (test_bit(R5_Wantdrain, &dev->flags))
                         xor_srcs[count++] = dev->page;
         }
 
@@ -649,16 +649,10 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 }
 
 static struct dma_async_tx_descriptor *
-ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
-                 unsigned long ops_request)
+ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 {
         int disks = sh->disks;
-        int pd_idx = sh->pd_idx, i;
-
-        /* check if prexor is active which means only process blocks
-         * that are part of a read-modify-write (Wantprexor)
-         */
-        int prexor = test_bit(STRIPE_OP_PREXOR, &ops_request);
+        int i;
 
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
@@ -666,20 +660,8 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
         for (i = disks; i--; ) {
                 struct r5dev *dev = &sh->dev[i];
                 struct bio *chosen;
-                int towrite;
 
-                towrite = 0;
-                if (prexor) { /* rmw */
-                        if (dev->towrite &&
-                            test_bit(R5_Wantprexor, &dev->flags))
-                                towrite = 1;
-                } else { /* rcw */
-                        if (i != pd_idx && dev->towrite &&
-                                test_bit(R5_LOCKED, &dev->flags))
-                                towrite = 1;
-                }
-
-                if (towrite) {
+                if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
                         struct bio *wbi;
 
                         spin_lock(&sh->lock);
@@ -704,18 +686,6 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
 static void ops_complete_postxor(void *stripe_head_ref)
 {
         struct stripe_head *sh = stripe_head_ref;
-
-        pr_debug("%s: stripe %llu\n", __func__,
-                (unsigned long long)sh->sector);
-
-        sh->reconstruct_state = reconstruct_state_result;
-        set_bit(STRIPE_HANDLE, &sh->state);
-        release_stripe(sh);
-}
-
-static void ops_complete_write(void *stripe_head_ref)
-{
-        struct stripe_head *sh = stripe_head_ref;
         int disks = sh->disks, i, pd_idx = sh->pd_idx;
 
         pr_debug("%s: stripe %llu\n", __func__,
@@ -727,14 +697,21 @@ static void ops_complete_write(void *stripe_head_ref)
                         set_bit(R5_UPTODATE, &dev->flags);
         }
 
-        sh->reconstruct_state = reconstruct_state_drain_result;
+        if (sh->reconstruct_state == reconstruct_state_drain_run)
+                sh->reconstruct_state = reconstruct_state_drain_result;
+        else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
+                sh->reconstruct_state = reconstruct_state_prexor_drain_result;
+        else {
+                BUG_ON(sh->reconstruct_state != reconstruct_state_run);
+                sh->reconstruct_state = reconstruct_state_result;
+        }
+
         set_bit(STRIPE_HANDLE, &sh->state);
         release_stripe(sh);
 }
 
 static void
-ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
-                unsigned long ops_request)
+ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 {
         /* kernel stack size limits the total number of disks */
         int disks = sh->disks;
@@ -742,9 +719,8 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
 
         int count = 0, pd_idx = sh->pd_idx, i;
         struct page *xor_dest;
-        int prexor = test_bit(STRIPE_OP_PREXOR, &ops_request);
+        int prexor = 0;
         unsigned long flags;
-        dma_async_tx_callback callback;
 
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
@@ -752,7 +728,8 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
         /* check if prexor is active which means only process blocks
          * that are part of a read-modify-write (written)
          */
-        if (prexor) {
+        if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+                prexor = 1;
                 xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
                 for (i = disks; i--; ) {
                         struct r5dev *dev = &sh->dev[i];
@@ -768,10 +745,6 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
                 }
         }
 
-        /* check whether this postxor is part of a write */
-        callback = test_bit(STRIPE_OP_BIODRAIN, &ops_request) ?
-                ops_complete_write : ops_complete_postxor;
-
         /* 1/ if we prexor'd then the dest is reused as a source
          * 2/ if we did not prexor then we are redoing the parity
          * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
@@ -785,10 +758,10 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
         if (unlikely(count == 1)) {
                 flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
                 tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
-                        flags, tx, callback, sh);
+                        flags, tx, ops_complete_postxor, sh);
         } else
                 tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
-                        flags, tx, callback, sh);
+                        flags, tx, ops_complete_postxor, sh);
 }
 
 static void ops_complete_check(void *stripe_head_ref)
@@ -847,12 +820,12 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
                 tx = ops_run_prexor(sh, tx);
 
         if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
-                tx = ops_run_biodrain(sh, tx, ops_request);
+                tx = ops_run_biodrain(sh, tx);
                 overlap_clear++;
         }
 
         if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
-                ops_run_postxor(sh, tx, ops_request);
+                ops_run_postxor(sh, tx);
 
         if (test_bit(STRIPE_OP_CHECK, &ops_request))
                 ops_run_check(sh);
@@ -1669,6 +1642,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
 
                         if (dev->towrite) {
                                 set_bit(R5_LOCKED, &dev->flags);
+                                set_bit(R5_Wantdrain, &dev->flags);
                                 if (!expand)
                                         clear_bit(R5_UPTODATE, &dev->flags);
                                 s->locked++;
@@ -1681,7 +1655,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
                 BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
                         test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
 
-                sh->reconstruct_state = reconstruct_state_drain_run;
+                sh->reconstruct_state = reconstruct_state_prexor_drain_run;
                 set_bit(STRIPE_OP_PREXOR, &s->ops_request);
                 set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
                 set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
@@ -1691,15 +1665,10 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
                         if (i == pd_idx)
                                 continue;
 
-                        /* For a read-modify write there may be blocks that are
-                         * locked for reading while others are ready to be
-                         * written so we distinguish these blocks by the
-                         * R5_Wantprexor bit
-                         */
                         if (dev->towrite &&
                             (test_bit(R5_UPTODATE, &dev->flags) ||
-                            test_bit(R5_Wantcompute, &dev->flags))) {
-                                set_bit(R5_Wantprexor, &dev->flags);
+                             test_bit(R5_Wantcompute, &dev->flags))) {
+                                set_bit(R5_Wantdrain, &dev->flags);
                                 set_bit(R5_LOCKED, &dev->flags);
                                 clear_bit(R5_UPTODATE, &dev->flags);
                                 s->locked++;
@@ -2660,11 +2629,11 @@ static void handle_stripe5(struct stripe_head *sh)
          * completed
          */
         prexor = 0;
-        if (sh->reconstruct_state == reconstruct_state_drain_result) {
+        if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
+                prexor = 1;
+        if (sh->reconstruct_state == reconstruct_state_drain_result ||
+            sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
                 sh->reconstruct_state = reconstruct_state_idle;
-                for (i = disks; i--; )
-                        prexor += test_and_clear_bit(R5_Wantprexor,
-                                                     &sh->dev[i].flags);
 
                 /* All the 'written' buffers and the parity block are ready to
                  * be written back to disk