md: rewrite handle_stripe_dirtying6 in asynchronous way

Rewrite handle_stripe_dirtying6 function to work asynchronously.

Signed-off-by Yuri Tikhonov <[email protected]>

Signed-off-by Ilya Yanok <[email protected]>

---
 drivers/md/raid5.c |  113 ++++++++++++++--------------------------------------
 1 files changed, 30 insertions(+), 83 deletions(-)

drivers/md/raid5.c +17 -12

index e08ed4f..f0b47bd 100644
@@ -2485,99 +2485,46 @@ static void handle_stripe_dirtying6(raid5_conf_t *conf,
               struct stripe_head *sh, struct stripe_head_state *s,
               struct r6_state *r6s, int disks)
 {
-       int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
+       int rcw = 0, pd_idx = sh->pd_idx, i;
       int qd_idx = r6s->qd_idx;
+
+       set_bit(STRIPE_HANDLE, &sh->state);
       for (i = disks; i--; ) {
               struct r5dev *dev = &sh->dev[i];
-               /* Would I have to read this buffer for reconstruct_write */
-               if (!test_bit(R5_OVERWRITE, &dev->flags)
-                   && i != pd_idx && i != qd_idx
-                   && (!test_bit(R5_LOCKED, &dev->flags)
-                           ) &&
-                   !test_bit(R5_UPTODATE, &dev->flags)) {
-                       if (test_bit(R5_Insync, &dev->flags)) rcw++;
-                       else {
-                               pr_debug("raid6: must_compute: "
-                                       "disk %d flags=%#lx\n", i, dev->flags);
-                               must_compute++;
+               /* check if we haven't enough data */
+               if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+                   i != pd_idx && i != qd_idx &&
+                   !test_bit(R5_LOCKED, &dev->flags) &&
+                   !(test_bit(R5_UPTODATE, &dev->flags) ||
+                     test_bit(R5_Wantcompute, &dev->flags))) {
+                       rcw++;
+                       if (!test_bit(R5_Insync, &dev->flags))
+                               continue; /* it's a failed drive */
+
+                       if (
+                         test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+                               pr_debug("Read_old stripe %llu "
+                                       "block %d for Reconstruct\n",

Rewrite handle_stripe_dirtying6 function to work asynchronously.

Signed-off-by Yuri Tikhonov <[email protected]>

Signed-off-by Ilya Yanok <[email protected]>

---
 drivers/md/raid5.c |  113 ++++++++++++++--------------------------------------
 1 files changed, 30 insertions(+), 83 deletions(-)

drivers/md/raid5.c +17 -12

index e08ed4f..f0b47bd 100644
@@ -2485,99 +2485,46 @@ static void handle_stripe_dirtying6(raid5_conf_t *conf,
               struct stripe_head *sh, struct stripe_head_state *s,
               struct r6_state *r6s, int disks)
 {
-       int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
+       int rcw = 0, pd_idx = sh->pd_idx, i;
       int qd_idx = r6s->qd_idx;
+
+       set_bit(STRIPE_HANDLE, &sh->state);
       for (i = disks; i--; ) {
               struct r5dev *dev = &sh->dev[i];
-               /* Would I have to read this buffer for reconstruct_write */
-               if (!test_bit(R5_OVERWRITE, &dev->flags)
-                   && i != pd_idx && i != qd_idx
-                   && (!test_bit(R5_LOCKED, &dev->flags)
-                           ) &&
-                   !test_bit(R5_UPTODATE, &dev->flags)) {
-                       if (test_bit(R5_Insync, &dev->flags)) rcw++;
-                       else {
-                               pr_debug("raid6: must_compute: "
-                                       "disk %d flags=%#lx\n", i, dev->flags);
-                               must_compute++;
+               /* check if we haven't enough data */
+               if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+                   i != pd_idx && i != qd_idx &&
+                   !test_bit(R5_LOCKED, &dev->flags) &&
+                   !(test_bit(R5_UPTODATE, &dev->flags) ||
+                     test_bit(R5_Wantcompute, &dev->flags))) {
+                       rcw++;
+                       if (!test_bit(R5_Insync, &dev->flags))
+                               continue; /* it's a failed drive */
+
+                       if (
+                         test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+                               pr_debug("Read_old stripe %llu "
+                                       "block %d for Reconstruct\n",

Rewrite handle_stripe_dirtying6 function to work asynchronously.

Signed-off-by Yuri Tikhonov <[email protected]>

Signed-off-by Ilya Yanok <[email protected]>

---
 drivers/md/raid5.c |  113 ++++++++++++++--------------------------------------
 1 files changed, 30 insertions(+), 83 deletions(-)

drivers/md/raid5.c +17 -12

index e08ed4f..f0b47bd 100644
@@ -2485,99 +2485,46 @@ static void handle_stripe_dirtying6(raid5_conf_t *conf,
               struct stripe_head *sh, struct stripe_head_state *s,
               struct r6_state *r6s, int disks)
 {
-       int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
+       int rcw = 0, pd_idx = sh->pd_idx, i;
       int qd_idx = r6s->qd_idx;
+
+       set_bit(STRIPE_HANDLE, &sh->state);
       for (i = disks; i--; ) {
               struct r5dev *dev = &sh->dev[i];
-               /* Would I have to read this buffer for reconstruct_write */
-               if (!test_bit(R5_OVERWRITE, &dev->flags)
-                   && i != pd_idx && i != qd_idx
-                   && (!test_bit(R5_LOCKED, &dev->flags)
-                           ) &&
-                   !test_bit(R5_UPTODATE, &dev->flags)) {
-                       if (test_bit(R5_Insync, &dev->flags)) rcw++;
-                       else {
-                               pr_debug("raid6: must_compute: "
-                                       "disk %d flags=%#lx\n", i, dev->flags);
-                               must_compute++;
+               /* check if we haven't enough data */
+               if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+                   i != pd_idx && i != qd_idx &&
+                   !test_bit(R5_LOCKED, &dev->flags) &&
+                   !(test_bit(R5_UPTODATE, &dev->flags) ||
+                     test_bit(R5_Wantcompute, &dev->flags))) {
+                       rcw++;
+                       if (!test_bit(R5_Insync, &dev->flags))
+                               continue; /* it's a failed drive */
+
+                       if (
+                         test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+                               pr_debug("Read_old stripe %llu "
+                                       "block %d for Reconstruct\n",

On Mon, Dec 8, 2008 at 2:57 PM, Yuri Tikhonov <[email protected]> wrote:
What's the reasoning behind changing the logic here, i.e. removing must_compute and such? I'd feel more comfortable seeing copy and paste where possible with cleanups separated out into their own patch.

Rewrite handle_stripe_dirtying6 function to work asynchronously.

Quoted 4 lines · Dan Williams

On Mon, Dec 8, 2008 at 2:57 PM, Yuri Tikhonov <[email protected]> wrote:
What's the reasoning behind changing the logic here, i.e. removing must_compute and such? I'd feel more comfortable seeing copy and paste where possible with cleanups separated out into their own patch.

Ok, I now see why this change was made. Please make this changelog more descriptive than "Rewrite handle_stripe_dirtying6 function to work asynchronously."

Quoted 5 lines · Dan Williams

On Mon, Dec 8, 2008 at 2:57 PM, Yuri Tikhonov <[email protected]> wrote:
What's the reasoning behind changing the logic here, i.e. removing must_compute and such? I'd feel more comfortable seeing copy and paste where possible with cleanups separated out into their own patch.

Ok, I now see why this change was made. Please make this changelog more descriptive than "Rewrite handle_stripe_dirtying6 function to work asynchronously."

Ack, could you please make the changelog more descriptive? and or add some of your benchmark results?

Quoted 3 lines

Ok, I now see why this change was made. Please make this changelog more descriptive than "Rewrite handle_stripe_dirtying6 function to work asynchronously."

Sure, how about the following:

"

md: rewrite handle_stripe_dirtying6 in asynchronous way

Processing stripe dirtying in asynchronous way requires some changes
to the handle_stripe_dirtying6() algorithm.

In the synchronous implementation of the stripe dirtying we processed
dirtying of a degraded stripe (with partially changed strip(s) located on the failed drive(s)) inside one handle_stripe_dirtying6() call:
- we computed the missed strips from the old parities, and thus got the fully up-to-date stripe, then
- we did reconstruction using the new data to write.

In the asynchronous case of handle_stripe_dirtying6() we don't
process anything right inside this function (since we under the lock), but only schedule the necessary operations with flags. Thus, if handle_stripe_dirtying6() is performed on the top of a degraded array we should schedule the reconstruction operation when the failed strips are marked (by previously called fetch_block6()) as to be computed (with the R5_Wantcompute flag), and all the other strips of the stripe are UPTODATE. The schedule_reconstruction() function will set the STRIPE_OP_POSTXOR flag [for new parity calculation], which is then handled in raid_run_ops() after the STRIPE_OP_COMPUTE_BLK one [which causes computing of the data missed].

"