md/raid5: fix 'out of memory' during raid cache recovery

This fixes the case when md array assembly fails because of raid cache recovery
unable to allocate a stripe, despite attempts to replay stripes and increase
cache size. This happens because stripes released by r5c_recovery_replay_stripes
and raid5_set_cache_size don't become available for allocation immediately.
Released stripes first are placed on conf->released_stripes list and require
md thread to merge them on conf->inactive_list before they can be allocated.

Patch allows final allocation attempt during cache recovery to wait for
new stripes to become availabe for allocation.

Cc: linux-raid@vger.kernel.org
Cc: Shaohua Li <shli@kernel.org>
Cc: linux-stable <stable@vger.kernel.org> # 4.10+
Fixes: b4c625c67362 ("md/r5cache: r5cache recovery: part 1")
Signed-off-by: Alexei Naberezhnov <anaberezhnov@fb.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index ec3a5ef7fee0b8c099e729d49ad4a0665eddad82..cbbe6b6535be89fefec626bf759ddfedae9cb07e 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1935,12 +1935,14 @@ out:
 }
 
 static struct stripe_head *
-r5c_recovery_alloc_stripe(struct r5conf *conf,
-                         sector_t stripe_sect)
+r5c_recovery_alloc_stripe(
+               struct r5conf *conf,
+               sector_t stripe_sect,
+               int noblock)
 {
        struct stripe_head *sh;
 
-       sh = raid5_get_active_stripe(conf, stripe_sect, 0, 1, 0);
+       sh = raid5_get_active_stripe(conf, stripe_sect, 0, noblock, 0);
        if (!sh)
                return NULL;  /* no more stripe available */
 
@@ -2150,7 +2152,7 @@ r5c_recovery_analyze_meta_block(struct r5l_log *log,
                                                stripe_sect);
 
                if (!sh) {
-                       sh = r5c_recovery_alloc_stripe(conf, stripe_sect);
+                       sh = r5c_recovery_alloc_stripe(conf, stripe_sect, 1);
                        /*
                         * cannot get stripe from raid5_get_active_stripe
                         * try replay some stripes
@@ -2159,20 +2161,29 @@ r5c_recovery_analyze_meta_block(struct r5l_log *log,
                                r5c_recovery_replay_stripes(
                                        cached_stripe_list, ctx);
                                sh = r5c_recovery_alloc_stripe(
-                                       conf, stripe_sect);
+                                       conf, stripe_sect, 1);
                        }
                        if (!sh) {
+                               int new_size = conf->min_nr_stripes * 2;
                                pr_debug("md/raid:%s: Increasing stripe cache size to %d to recovery data on journal.\n",
                                        mdname(mddev),
-                                       conf->min_nr_stripes * 2);
-                               raid5_set_cache_size(mddev,
-                                                    conf->min_nr_stripes * 2);
-                               sh = r5c_recovery_alloc_stripe(conf,
-                                                              stripe_sect);
+                                       new_size);
+                               ret = raid5_set_cache_size(mddev, new_size);
+                               if (conf->min_nr_stripes <= new_size / 2) {
+                                       pr_err("md/raid:%s: Cannot increase cache size, ret=%d, new_size=%d, min_nr_stripes=%d, max_nr_stripes=%d\n",
+                                               mdname(mddev),
+                                               ret,
+                                               new_size,
+                                               conf->min_nr_stripes,
+                                               conf->max_nr_stripes);
+                                       return -ENOMEM;
+                               }
+                               sh = r5c_recovery_alloc_stripe(
+                                       conf, stripe_sect, 0);
                        }
                        if (!sh) {
                                pr_err("md/raid:%s: Cannot get enough stripes due to memory pressure. Recovery failed.\n",
-                                      mdname(mddev));
+                                       mdname(mddev));
                                return -ENOMEM;
                        }
                        list_add_tail(&sh->lru, cached_stripe_list);

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 4990f0319f6cf729165a2c55a73aaf7e9bf3f567..cecea901ab8c5f666a7eb7ea4c345323efcbff1a 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6369,6 +6369,7 @@ raid5_show_stripe_cache_size(struct mddev *mddev, char *page)
 int
 raid5_set_cache_size(struct mddev *mddev, int size)
 {
+       int result = 0;
        struct r5conf *conf = mddev->private;
 
        if (size <= 16 || size > 32768)
@@ -6385,11 +6386,14 @@ raid5_set_cache_size(struct mddev *mddev, int size)
 
        mutex_lock(&conf->cache_size_mutex);
        while (size > conf->max_nr_stripes)
-               if (!grow_one_stripe(conf, GFP_KERNEL))
+               if (!grow_one_stripe(conf, GFP_KERNEL)) {
+                       conf->min_nr_stripes = conf->max_nr_stripes;
+                       result = -ENOMEM;
                        break;
+               }
        mutex_unlock(&conf->cache_size_mutex);
 
-       return 0;
+       return result;
 }
 EXPORT_SYMBOL(raid5_set_cache_size);