Re: [PATCH v3 5/5] md/raid10: convert resync_lock to use seqlock
From: Guoqing Jiang <hidden>
Date: 2022-09-18 11:36:43
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On 9/16/22 7:34 PM, Yu Kuai wrote:
quoted hunk ↗ jump to hunk
From: Yu Kuai <redacted> Currently, wait_barrier() will hold 'resync_lock' to read 'conf->barrier', and io can't be dispatched until 'barrier' is dropped. Since holding the 'barrier' is not common, convert 'resync_lock' to use seqlock so that holding lock can be avoided in fast path. Signed-off-by: Yu Kuai <redacted> --- drivers/md/raid10.c | 87 ++++++++++++++++++++++++++++++--------------- drivers/md/raid10.h | 2 +- 2 files changed, 59 insertions(+), 30 deletions(-)diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 9a28abd19709..2daa7d57034c 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c@@ -79,6 +79,21 @@ static void end_reshape(struct r10conf *conf); #include "raid1-10.c" +#define NULL_CMD +#define cmd_before(conf, cmd) \ + do { \ + write_sequnlock_irq(&(conf)->resync_lock); \ + cmd; \ + } while (0) +#define cmd_after(conf) write_seqlock_irq(&(conf)->resync_lock)
The two is not paired well given only cmd_before needs the 'cmd'.
+ +#define wait_event_barrier_cmd(conf, cond, cmd) \ + wait_event_cmd((conf)->wait_barrier, cond, cmd_before(conf, cmd), \ + cmd_after(conf)) + +#define wait_event_barrier(conf, cond) \ + wait_event_barrier_cmd(conf, cond, NULL_CMD)
What is the issue without define NULL_CMD? Thanks, Guoqing