From d95901433436aeb921eac58bfd8a2aa77f110384 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 2 Feb 2015 17:08:03 +1100 Subject: md/bitmap: fix a might_sleep() warning. commit 8eb23b9f35aae413140d3fda766a98092c21e9b0 sched: Debug nested sleeps causes false-positive warnings in RAID5 code. This annotation removes them and adds a comment explaining why there is no real problem. Reported-by: Fengguang Wu Signed-off-by: NeilBrown --- drivers/md/bitmap.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'drivers/md/bitmap.c') diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index da3604e73e8a..1695ee5f3ffc 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -72,6 +72,19 @@ __acquires(bitmap->lock) /* this page has not been allocated yet */ spin_unlock_irq(&bitmap->lock); + /* It is possible that this is being called inside a + * prepare_to_wait/finish_wait loop from raid5c:make_request(). + * In general it is not permitted to sleep in that context as it + * can cause the loop to spin freely. + * That doesn't apply here as we can only reach this point + * once with any loop. + * When this function completes, either bp[page].map or + * bp[page].hijacked. In either case, this function will + * abort before getting to this point again. So there is + * no risk of a free-spin, and so it is safe to assert + * that sleeping here is allowed. + */ + sched_annotate_sleep(); mappage = kzalloc(PAGE_SIZE, GFP_NOIO); spin_lock_irq(&bitmap->lock); -- cgit v1.2.3 From 978a7a47cae79ae7a7b5a1e80bfcaef6ee700312 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 15 Dec 2014 12:56:58 +1100 Subject: md/bitmap: protect clearing of ->bitmap by mddev->lock This makes it safe to inspect the struct while holding only the spinlock. Signed-off-by: NeilBrown --- drivers/md/bitmap.c | 2 ++ drivers/md/md.h | 1 + 2 files changed, 3 insertions(+) (limited to 'drivers/md/bitmap.c') diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index 1695ee5f3ffc..3424b1915fc4 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -1619,7 +1619,9 @@ void bitmap_destroy(struct mddev *mddev) return; mutex_lock(&mddev->bitmap_info.mutex); + spin_lock(&mddev->lock); mddev->bitmap = NULL; /* disconnect from the md device */ + spin_unlock(&mddev->lock); mutex_unlock(&mddev->bitmap_info.mutex); if (mddev->thread) mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT; diff --git a/drivers/md/md.h b/drivers/md/md.h index e41559dccdc9..8770308a8052 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -392,6 +392,7 @@ struct mddev { * clearing MD_CHANGE_* * in_sync - and related safemode and MD_CHANGE changes * pers (also protected by reconfig_mutex and pending IO). + * clearing ->bitmap */ spinlock_t lock; wait_queue_head_t sb_wait; /* for waiting on superblock updates */ -- cgit v1.2.3 From b7b17c9b67e5984210c83d50d2c8117d3bd50ea0 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 15 Dec 2014 12:56:59 +1100 Subject: md: remove mddev_lock() from md_attr_show() Most attributes can be read safely without any locking. A race might lead to a slightly out-dated value, but nothing wrong. We already have locking in some places where needed. All that remains is can_clear_show(), behind_writes_used_show() and action_show() which are easily fixed. Signed-off-by: NeilBrown --- drivers/md/bitmap.c | 13 ++++++++++--- drivers/md/md.c | 23 ++++++++++------------- 2 files changed, 20 insertions(+), 16 deletions(-) (limited to 'drivers/md/bitmap.c') diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index 3424b1915fc4..3a5767968ba0 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -2211,11 +2211,13 @@ __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store); static ssize_t can_clear_show(struct mddev *mddev, char *page) { int len; + spin_lock(&mddev->lock); if (mddev->bitmap) len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ? "false" : "true")); else len = sprintf(page, "\n"); + spin_unlock(&mddev->lock); return len; } @@ -2240,10 +2242,15 @@ __ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store); static ssize_t behind_writes_used_show(struct mddev *mddev, char *page) { + ssize_t ret; + spin_lock(&mddev->lock); if (mddev->bitmap == NULL) - return sprintf(page, "0\n"); - return sprintf(page, "%lu\n", - mddev->bitmap->behind_writes_used); + ret = sprintf(page, "0\n"); + else + ret = sprintf(page, "%lu\n", + mddev->bitmap->behind_writes_used); + spin_unlock(&mddev->lock); + return ret; } static ssize_t diff --git a/drivers/md/md.c b/drivers/md/md.c index eb0c3b576d7d..dbbe5e6df24c 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4042,20 +4042,21 @@ static ssize_t action_show(struct mddev *mddev, char *page) { char *type = "idle"; - if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) + unsigned long recovery = mddev->recovery; + if (test_bit(MD_RECOVERY_FROZEN, &recovery)) type = "frozen"; - else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) || - (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) { - if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) + else if (test_bit(MD_RECOVERY_RUNNING, &recovery) || + (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &recovery))) { + if (test_bit(MD_RECOVERY_RESHAPE, &recovery)) type = "reshape"; - else if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) { - if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) + else if (test_bit(MD_RECOVERY_SYNC, &recovery)) { + if (!test_bit(MD_RECOVERY_REQUESTED, &recovery)) type = "resync"; - else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)) + else if (test_bit(MD_RECOVERY_CHECK, &recovery)) type = "check"; else type = "repair"; - } else if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery)) + } else if (test_bit(MD_RECOVERY_RECOVER, &recovery)) type = "recover"; } return sprintf(page, "%s\n", type); @@ -4572,11 +4573,7 @@ md_attr_show(struct kobject *kobj, struct attribute *attr, char *page) mddev_get(mddev); spin_unlock(&all_mddevs_lock); - rv = mddev_lock(mddev); - if (!rv) { - rv = entry->show(mddev, page); - mddev_unlock(mddev); - } + rv = entry->show(mddev, page); mddev_put(mddev); return rv; } -- cgit v1.2.3