[md PATCH 06/34] md/raid5: Remove use of sh->lock in sync_request

This is the start of a series of patches to remove sh->lock.

sync_request takes sh->lock before setting STRIPE_SYNCING to ensure
there is no race with testing it in handle_stripe[56].

Instead, use a new flag STRIPE_SYNC_REQUESTED and test it early
in handle_stripe[56] (after getting the same lock) and perform the
same set/clear operations if it was set.

Signed-off-by: NeilBrown
---

drivers/md/raid5.c | 13 +++++++++----
drivers/md/raid5.h | 33 ++++++++++++++++++---------------
2 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 7148064..f2f2ab3 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3022,6 +3022,10 @@ static void handle_stripe5(struct stripe_head *sh)
sh->reconstruct_state);

spin_lock(&sh->lock);
+ if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
+ set_bit(STRIPE_SYNCING, &sh->state);
+ clear_bit(STRIPE_INSYNC, &sh->state);
+ }
clear_bit(STRIPE_HANDLE, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);

@@ -3313,6 +3317,10 @@ static void handle_stripe6(struct stripe_head *sh)
memset(&s, 0, sizeof(s));

spin_lock(&sh->lock);
+ if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
+ set_bit(STRIPE_SYNCING, &sh->state);
+ clear_bit(STRIPE_INSYNC, &sh->state);
+ }
clear_bit(STRIPE_HANDLE, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);

@@ -4373,10 +4381,7 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski

bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);

- spin_lock(&sh->lock);
- set_bit(STRIPE_SYNCING, &sh->state);
- clear_bit(STRIPE_INSYNC, &sh->state);
- spin_unlock(&sh->lock);
+ set_bit(STRIPE_SYNC_REQUESTED, &sh->state);

handle_stripe(sh);
release_stripe(sh);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 3ca77a2..a330011 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -289,21 +289,24 @@ struct r6_state {
/*
* Stripe state
*/
-#define STRIPE_HANDLE 2
-#define STRIPE_SYNCING 3
-#define STRIPE_INSYNC 4
-#define STRIPE_PREREAD_ACTIVE 5
-#define STRIPE_DELAYED 6
-#define STRIPE_DEGRADED 7
-#define STRIPE_BIT_DELAY 8
-#define STRIPE_EXPANDING 9
-#define STRIPE_EXPAND_SOURCE 10
-#define STRIPE_EXPAND_READY 11
-#define STRIPE_IO_STARTED 12 /* do not count towards 'bypass_count' */
-#define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */
-#define STRIPE_BIOFILL_RUN 14
-#define STRIPE_COMPUTE_RUN 15
-#define STRIPE_OPS_REQ_PENDING 16
+enum {
+ STRIPE_HANDLE,
+ STRIPE_SYNC_REQUESTED,
+ STRIPE_SYNCING,
+ STRIPE_INSYNC,
+ STRIPE_PREREAD_ACTIVE,
+ STRIPE_DELAYED,
+ STRIPE_DEGRADED,
+ STRIPE_BIT_DELAY,
+ STRIPE_EXPANDING,
+ STRIPE_EXPAND_SOURCE,
+ STRIPE_EXPAND_READY,
+ STRIPE_IO_STARTED, /* do not count towards 'bypass_count' */
+ STRIPE_FULL_WRITE, /* all blocks are set to be overwritten */
+ STRIPE_BIOFILL_RUN,
+ STRIPE_COMPUTE_RUN,
+ STRIPE_OPS_REQ_PENDING,
+};

/*
* Operation request flags


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