md/raid1-10: limit the number of plugged bio

bio can be added to plug infinitely, and following writeback test can
trigger huge amount of plugged bio:

Test script:
modprobe brd rd_nr=4 rd_size=10485760
mdadm -CR /dev/md0 -l10 -n4 /dev/ram[0123] --assume-clean --bitmap=internal
echo 0 > /proc/sys/vm/dirty_background_ratio
fio -filename=/dev/md0 -ioengine=libaio -rw=write -bs=4k -numjobs=1 -iodepth=128 -name=test

Test result:
Monitor /sys/block/md0/inflight will found that inflight keep increasing
until fio finish writing, after running for about 2 minutes:

[root@fedora ~]# cat /sys/block/md0/inflight
       0  4474191

Fix the problem by limiting the number of plugged bio based on the number
of copies for original bio.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230529131106.2123367-8-yukuai1@huaweicloud.com

diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
index c62bcb17c67bb1f31b7e0264581ea921392ef56e..169ebe296f2d0cdb433a83676bbcdcd5100494c4 100644 (file)
--- a/drivers/md/raid1-10.c
+++ b/drivers/md/raid1-10.c
@@ -21,6 +21,7 @@
 #define IO_MADE_GOOD ((struct bio *)2)
 
 #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
+#define MAX_PLUG_BIO 32
 
 /* for managing resync I/O pages */
 struct resync_pages {
@@ -31,6 +32,7 @@ struct resync_pages {
 struct raid1_plug_cb {
        struct blk_plug_cb      cb;
        struct bio_list         pending;
+       unsigned int            count;
 };
 
 static void rbio_pool_free(void *rbio, void *data)
@@ -129,7 +131,7 @@ static inline void raid1_submit_write(struct bio *bio)
 }
 
 static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
-                                     blk_plug_cb_fn unplug)
+                                     blk_plug_cb_fn unplug, int copies)
 {
        struct raid1_plug_cb *plug = NULL;
        struct blk_plug_cb *cb;
@@ -149,6 +151,11 @@ static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
 
        plug = container_of(cb, struct raid1_plug_cb, cb);
        bio_list_add(&plug->pending, bio);
+       if (++plug->count / MAX_PLUG_BIO >= copies) {
+               list_del(&cb->list);
+               cb->callback(cb, false);
+       }
+
 
        return true;
 }

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 334ed76d3c5abfa463e0659f9a65e12881567265..dd25832eb04527072a25b1bf098a3873a203db6d 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1565,7 +1565,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
                                              r1_bio->sector);
                /* flush_pending_writes() needs access to the rdev so...*/
                mbio->bi_bdev = (void *)rdev;
-               if (!raid1_add_bio_to_plug(mddev, mbio, raid1_unplug)) {
+               if (!raid1_add_bio_to_plug(mddev, mbio, raid1_unplug, disks)) {
                        spin_lock_irqsave(&conf->device_lock, flags);
                        bio_list_add(&conf->pending_bio_list, mbio);
                        spin_unlock_irqrestore(&conf->device_lock, flags);

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index f890f549086bac19a5502414c8e99743733df3a8..d0de8c9fb3cfbd2d784574a1c8b9ff080fd6357e 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1314,7 +1314,7 @@ static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
 
        atomic_inc(&r10_bio->remaining);
 
-       if (!raid1_add_bio_to_plug(mddev, mbio, raid10_unplug)) {
+       if (!raid1_add_bio_to_plug(mddev, mbio, raid10_unplug, conf->copies)) {
                spin_lock_irqsave(&conf->device_lock, flags);
                bio_list_add(&conf->pending_bio_list, mbio);
                spin_unlock_irqrestore(&conf->device_lock, flags);