md: make reconfig_mutex optional for writes to md sysfs files.

Rather than using mddev_lock() to take the reconfig_mutex
when writing to any md sysfs file, we only take mddev_lock()
in the particular _store() functions that require it.
Admittedly this is most, but it isn't all.

This also allows us to remove special-case handling for new_dev_store
(in md_attr_store).

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index ea839d8..c8d2bac 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3256,26 +3256,32 @@ static ssize_t
 level_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char clevel[16];
-       ssize_t rv = len;
+       ssize_t rv;
+       size_t slen = len;
        struct md_personality *pers, *oldpers;
        long level;
        void *priv, *oldpriv;
        struct md_rdev *rdev;
 
+       if (slen == 0 || slen >= sizeof(clevel))
+               return -EINVAL;
+
+       rv = mddev_lock(mddev);
+       if (rv)
+               return rv;
+
        if (mddev->pers == NULL) {
-               if (len == 0)
-                       return 0;
-               if (len >= sizeof(mddev->clevel))
-                       return -ENOSPC;
-               strncpy(mddev->clevel, buf, len);
-               if (mddev->clevel[len-1] == '\n')
-                       len--;
-               mddev->clevel[len] = 0;
+               strncpy(mddev->clevel, buf, slen);
+               if (mddev->clevel[slen-1] == '\n')
+                       slen--;
+               mddev->clevel[slen] = 0;
                mddev->level = LEVEL_NONE;
-               return rv;
+               rv = len;
+               goto out_unlock;
        }
+       rv = -EROFS;
        if (mddev->ro)
-               return  -EROFS;
+               goto out_unlock;
 
        /* request to change the personality.  Need to ensure:
         *  - array is not engaged in resync/recovery/reshape
@@ -3283,25 +3289,25 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
         *  - new personality will access other array.
         */
 
+       rv = -EBUSY;
        if (mddev->sync_thread ||
            test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
            mddev->reshape_position != MaxSector ||
            mddev->sysfs_active)
-               return -EBUSY;
+               goto out_unlock;
 
+       rv = -EINVAL;
        if (!mddev->pers->quiesce) {
                printk(KERN_WARNING "md: %s: %s does not support online personality change\n",
                       mdname(mddev), mddev->pers->name);
-               return -EINVAL;
+               goto out_unlock;
        }
 
        /* Now find the new personality */
-       if (len == 0 || len >= sizeof(clevel))
-               return -EINVAL;
-       strncpy(clevel, buf, len);
-       if (clevel[len-1] == '\n')
-               len--;
-       clevel[len] = 0;
+       strncpy(clevel, buf, slen);
+       if (clevel[slen-1] == '\n')
+               slen--;
+       clevel[slen] = 0;
        if (kstrtol(clevel, 10, &level))
                level = LEVEL_NONE;
 
@@ -3312,20 +3318,23 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
        if (!pers || !try_module_get(pers->owner)) {
                spin_unlock(&pers_lock);
                printk(KERN_WARNING "md: personality %s not loaded\n", clevel);
-               return -EINVAL;
+               rv = -EINVAL;
+               goto out_unlock;
        }
        spin_unlock(&pers_lock);
 
        if (pers == mddev->pers) {
                /* Nothing to do! */
                module_put(pers->owner);
-               return rv;
+               rv = len;
+               goto out_unlock;
        }
        if (!pers->takeover) {
                module_put(pers->owner);
                printk(KERN_WARNING "md: %s: %s does not support personality takeover\n",
                       mdname(mddev), clevel);
-               return -EINVAL;
+               rv = -EINVAL;
+               goto out_unlock;
        }
 
        rdev_for_each(rdev, mddev)
@@ -3345,7 +3354,8 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
                module_put(pers->owner);
                printk(KERN_WARNING "md: %s: %s would not accept array\n",
                       mdname(mddev), clevel);
-               return PTR_ERR(priv);
+               rv = PTR_ERR(priv);
+               goto out_unlock;
        }
 
        /* Looks like we have a winner */
@@ -3438,6 +3448,9 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
                md_update_sb(mddev, 1);
        sysfs_notify(&mddev->kobj, NULL, "level");
        md_new_event(mddev);
+       rv = len;
+out_unlock:
+       mddev_unlock(mddev);
        return rv;
 }
 
@@ -3460,28 +3473,32 @@ layout_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char *e;
        unsigned long n = simple_strtoul(buf, &e, 10);
+       int err;
 
        if (!*buf || (*e && *e != '\n'))
                return -EINVAL;
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
 
        if (mddev->pers) {
-               int err;
                if (mddev->pers->check_reshape == NULL)
-                       return -EBUSY;
-               if (mddev->ro)
-                       return -EROFS;
-               mddev->new_layout = n;
-               err = mddev->pers->check_reshape(mddev);
-               if (err) {
-                       mddev->new_layout = mddev->layout;
-                       return err;
+                       err = -EBUSY;
+               else if (mddev->ro)
+                       err = -EROFS;
+               else {
+                       mddev->new_layout = n;
+                       err = mddev->pers->check_reshape(mddev);
+                       if (err)
+                               mddev->new_layout = mddev->layout;
                }
        } else {
                mddev->new_layout = n;
                if (mddev->reshape_position == MaxSector)
                        mddev->layout = n;
        }
-       return len;
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_layout =
 __ATTR(layout, S_IRUGO|S_IWUSR, layout_show, layout_store);
@@ -3504,32 +3521,39 @@ static ssize_t
 raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char *e;
-       int rv = 0;
+       int err;
        unsigned long n = simple_strtoul(buf, &e, 10);
 
        if (!*buf || (*e && *e != '\n'))
                return -EINVAL;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (mddev->pers)
-               rv = update_raid_disks(mddev, n);
+               err = update_raid_disks(mddev, n);
        else if (mddev->reshape_position != MaxSector) {
                struct md_rdev *rdev;
                int olddisks = mddev->raid_disks - mddev->delta_disks;
 
+               err = -EINVAL;
                rdev_for_each(rdev, mddev) {
                        if (olddisks < n &&
                            rdev->data_offset < rdev->new_data_offset)
-                               return -EINVAL;
+                               goto out_unlock;
                        if (olddisks > n &&
                            rdev->data_offset > rdev->new_data_offset)
-                               return -EINVAL;
+                               goto out_unlock;
                }
+               err = 0;
                mddev->delta_disks = n - olddisks;
                mddev->raid_disks = n;
                mddev->reshape_backwards = (mddev->delta_disks < 0);
        } else
                mddev->raid_disks = n;
-       return rv ? rv : len;
+out_unlock:
+       mddev_unlock(mddev);
+       return err ? err : len;
 }
 static struct md_sysfs_entry md_raid_disks =
 __ATTR(raid_disks, S_IRUGO|S_IWUSR, raid_disks_show, raid_disks_store);
@@ -3548,30 +3572,34 @@ chunk_size_show(struct mddev *mddev, char *page)
 static ssize_t
 chunk_size_store(struct mddev *mddev, const char *buf, size_t len)
 {
+       int err;
        char *e;
        unsigned long n = simple_strtoul(buf, &e, 10);
 
        if (!*buf || (*e && *e != '\n'))
                return -EINVAL;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (mddev->pers) {
-               int err;
                if (mddev->pers->check_reshape == NULL)
-                       return -EBUSY;
-               if (mddev->ro)
-                       return -EROFS;
-               mddev->new_chunk_sectors = n >> 9;
-               err = mddev->pers->check_reshape(mddev);
-               if (err) {
-                       mddev->new_chunk_sectors = mddev->chunk_sectors;
-                       return err;
+                       err = -EBUSY;
+               else if (mddev->ro)
+                       err = -EROFS;
+               else {
+                       mddev->new_chunk_sectors = n >> 9;
+                       err = mddev->pers->check_reshape(mddev);
+                       if (err)
+                               mddev->new_chunk_sectors = mddev->chunk_sectors;
                }
        } else {
                mddev->new_chunk_sectors = n >> 9;
                if (mddev->reshape_position == MaxSector)
                        mddev->chunk_sectors = n >> 9;
        }
-       return len;
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_chunk_size =
 __ATTR(chunk_size, S_IRUGO|S_IWUSR, chunk_size_show, chunk_size_store);
@@ -3587,20 +3615,27 @@ resync_start_show(struct mddev *mddev, char *page)
 static ssize_t
 resync_start_store(struct mddev *mddev, const char *buf, size_t len)
 {
+       int err;
        char *e;
        unsigned long long n = simple_strtoull(buf, &e, 10);
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (mddev->pers && !test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
-               return -EBUSY;
-       if (cmd_match(buf, "none"))
+               err = -EBUSY;
+       else if (cmd_match(buf, "none"))
                n = MaxSector;
        else if (!*buf || (*e && *e != '\n'))
-               return -EINVAL;
+               err = -EINVAL;
 
-       mddev->recovery_cp = n;
-       if (mddev->pers)
-               set_bit(MD_CHANGE_CLEAN, &mddev->flags);
-       return len;
+       if (!err) {
+               mddev->recovery_cp = n;
+               if (mddev->pers)
+                       set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+       }
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_resync_start =
 __ATTR(resync_start, S_IRUGO|S_IWUSR, resync_start_show, resync_start_store);
@@ -3698,8 +3733,39 @@ static int restart_array(struct mddev *mddev);
 static ssize_t
 array_state_store(struct mddev *mddev, const char *buf, size_t len)
 {
-       int err = -EINVAL;
+       int err;
        enum array_state st = match_word(buf, array_states);
+
+       if (mddev->pers && (st == active || st == clean) && mddev->ro != 1) {
+               /* don't take reconfig_mutex when toggling between
+                * clean and active
+                */
+               spin_lock(&mddev->lock);
+               if (st == active) {
+                       restart_array(mddev);
+                       clear_bit(MD_CHANGE_PENDING, &mddev->flags);
+                       wake_up(&mddev->sb_wait);
+                       err = 0;
+               } else /* st == clean */ {
+                       restart_array(mddev);
+                       if (atomic_read(&mddev->writes_pending) == 0) {
+                               if (mddev->in_sync == 0) {
+                                       mddev->in_sync = 1;
+                                       if (mddev->safemode == 1)
+                                               mddev->safemode = 0;
+                                       set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+                               }
+                               err = 0;
+                       } else
+                               err = -EBUSY;
+               }
+               spin_unlock(&mddev->lock);
+               return err;
+       }
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       err = -EINVAL;
        switch(st) {
        case bad_word:
                break;
@@ -3775,14 +3841,14 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
                /* these cannot be set */
                break;
        }
-       if (err)
-               return err;
-       else {
+
+       if (!err) {
                if (mddev->hold_active == UNTIL_IOCTL)
                        mddev->hold_active = 0;
                sysfs_notify_dirent_safe(mddev->sysfs_state);
-               return len;
        }
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_array_state =
 __ATTR(array_state, S_IRUGO|S_IWUSR, array_state_show, array_state_store);
@@ -3843,6 +3909,11 @@ new_dev_store(struct mddev *mddev, const char *buf, size_t len)
            minor != MINOR(dev))
                return -EOVERFLOW;
 
+       flush_workqueue(md_misc_wq);
+
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (mddev->persistent) {
                rdev = md_import_device(dev, mddev->major_version,
                                        mddev->minor_version);
@@ -3866,6 +3937,7 @@ new_dev_store(struct mddev *mddev, const char *buf, size_t len)
  out:
        if (err)
                export_rdev(rdev);
+       mddev_unlock(mddev);
        return err ? err : len;
 }
 
@@ -3877,7 +3949,11 @@ bitmap_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char *end;
        unsigned long chunk, end_chunk;
+       int err;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (!mddev->bitmap)
                goto out;
        /* buf should be <chunk> <chunk> ... or <chunk>-<chunk> ... (range) */
@@ -3895,6 +3971,7 @@ bitmap_store(struct mddev *mddev, const char *buf, size_t len)
        }
        bitmap_unplug(mddev->bitmap); /* flush the bits to disk */
 out:
+       mddev_unlock(mddev);
        return len;
 }
 
@@ -3922,6 +3999,9 @@ size_store(struct mddev *mddev, const char *buf, size_t len)
 
        if (err < 0)
                return err;
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        if (mddev->pers) {
                err = update_size(mddev, sectors);
                md_update_sb(mddev, 1);
@@ -3932,6 +4012,7 @@ size_store(struct mddev *mddev, const char *buf, size_t len)
                else
                        err = -ENOSPC;
        }
+       mddev_unlock(mddev);
        return err ? err : len;
 }
 
@@ -3961,21 +4042,28 @@ metadata_store(struct mddev *mddev, const char *buf, size_t len)
 {
        int major, minor;
        char *e;
+       int err;
        /* Changing the details of 'external' metadata is
         * always permitted.  Otherwise there must be
         * no devices attached to the array.
         */
+
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       err = -EBUSY;
        if (mddev->external && strncmp(buf, "external:", 9) == 0)
                ;
        else if (!list_empty(&mddev->disks))
-               return -EBUSY;
+               goto out_unlock;
 
+       err = 0;
        if (cmd_match(buf, "none")) {
                mddev->persistent = 0;
                mddev->external = 0;
                mddev->major_version = 0;
                mddev->minor_version = 90;
-               return len;
+               goto out_unlock;
        }
        if (strncmp(buf, "external:", 9) == 0) {
                size_t namelen = len-9;
@@ -3989,22 +4077,27 @@ metadata_store(struct mddev *mddev, const char *buf, size_t len)
                mddev->external = 1;
                mddev->major_version = 0;
                mddev->minor_version = 90;
-               return len;
+               goto out_unlock;
        }
        major = simple_strtoul(buf, &e, 10);
+       err = -EINVAL;
        if (e==buf || *e != '.')
-               return -EINVAL;
+               goto out_unlock;
        buf = e+1;
        minor = simple_strtoul(buf, &e, 10);
        if (e==buf || (*e && *e != '\n') )
-               return -EINVAL;
+               goto out_unlock;
+       err = -ENOENT;
        if (major >= ARRAY_SIZE(super_types) || super_types[major].name == NULL)
-               return -ENOENT;
+               goto out_unlock;
        mddev->major_version = major;
        mddev->minor_version = minor;
        mddev->persistent = 1;
        mddev->external = 0;
-       return len;
+       err = 0;
+out_unlock:
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry md_metadata =
@@ -4049,7 +4142,10 @@ action_store(struct mddev *mddev, const char *page, size_t len)
                flush_workqueue(md_misc_wq);
                if (mddev->sync_thread) {
                        set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-                       md_reap_sync_thread(mddev);
+                       if (mddev_lock(mddev) == 0) {
+                               md_reap_sync_thread(mddev);
+                               mddev_unlock(mddev);
+                       }
                }
        } else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
                   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
@@ -4063,7 +4159,11 @@ action_store(struct mddev *mddev, const char *page, size_t len)
                int err;
                if (mddev->pers->start_reshape == NULL)
                        return -EINVAL;
-               err = mddev->pers->start_reshape(mddev);
+               err = mddev_lock(mddev);
+               if (!err) {
+                       err = mddev->pers->start_reshape(mddev);
+                       mddev_unlock(mddev);
+               }
                if (err)
                        return err;
                sysfs_notify(&mddev->kobj, NULL, "degraded");
@@ -4346,14 +4446,20 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
-       unsigned long long old = mddev->suspend_lo;
+       unsigned long long old;
+       int err;
 
-       if (mddev->pers == NULL ||
-           mddev->pers->quiesce == NULL)
-               return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       err = -EINVAL;
+       if (mddev->pers == NULL ||
+           mddev->pers->quiesce == NULL)
+               goto unlock;
+       old = mddev->suspend_lo;
        mddev->suspend_lo = new;
        if (new >= old)
                /* Shrinking suspended region */
@@ -4363,7 +4469,10 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
                mddev->pers->quiesce(mddev, 1);
                mddev->pers->quiesce(mddev, 0);
        }
-       return len;
+       err = 0;
+unlock:
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_suspend_lo =
 __ATTR(suspend_lo, S_IRUGO|S_IWUSR, suspend_lo_show, suspend_lo_store);
@@ -4379,14 +4488,20 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
 {
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
-       unsigned long long old = mddev->suspend_hi;
+       unsigned long long old;
+       int err;
 
-       if (mddev->pers == NULL ||
-           mddev->pers->quiesce == NULL)
-               return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       err = -EINVAL;
+       if (mddev->pers == NULL ||
+           mddev->pers->quiesce == NULL)
+               goto unlock;
+       old = mddev->suspend_hi;
        mddev->suspend_hi = new;
        if (new <= old)
                /* Shrinking suspended region */
@@ -4396,7 +4511,10 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
                mddev->pers->quiesce(mddev, 1);
                mddev->pers->quiesce(mddev, 0);
        }
-       return len;
+       err = 0;
+unlock:
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 static struct md_sysfs_entry md_suspend_hi =
 __ATTR(suspend_hi, S_IRUGO|S_IWUSR, suspend_hi_show, suspend_hi_store);
@@ -4416,11 +4534,17 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
 {
        struct md_rdev *rdev;
        char *e;
+       int err;
        unsigned long long new = simple_strtoull(buf, &e, 10);
-       if (mddev->pers)
-               return -EBUSY;
+
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       err = -EBUSY;
+       if (mddev->pers)
+               goto unlock;
        mddev->reshape_position = new;
        mddev->delta_disks = 0;
        mddev->reshape_backwards = 0;
@@ -4429,7 +4553,10 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
        mddev->new_chunk_sectors = mddev->chunk_sectors;
        rdev_for_each(rdev, mddev)
                rdev->new_data_offset = rdev->data_offset;
-       return len;
+       err = 0;
+unlock:
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry md_reshape_position =
@@ -4447,6 +4574,8 @@ static ssize_t
 reshape_direction_store(struct mddev *mddev, const char *buf, size_t len)
 {
        int backwards = 0;
+       int err;
+
        if (cmd_match(buf, "forwards"))
                backwards = 0;
        else if (cmd_match(buf, "backwards"))
@@ -4456,16 +4585,19 @@ reshape_direction_store(struct mddev *mddev, const char *buf, size_t len)
        if (mddev->reshape_backwards == backwards)
                return len;
 
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
        /* check if we are allowed to change */
        if (mddev->delta_disks)
-               return -EBUSY;
-
-       if (mddev->persistent &&
+               err = -EBUSY;
+       else if (mddev->persistent &&
            mddev->major_version == 0)
-               return -EINVAL;
-
-       mddev->reshape_backwards = backwards;
-       return len;
+               err =  -EINVAL;
+       else
+               mddev->reshape_backwards = backwards;
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry md_reshape_direction =
@@ -4486,6 +4618,11 @@ static ssize_t
 array_size_store(struct mddev *mddev, const char *buf, size_t len)
 {
        sector_t sectors;
+       int err;
+
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
 
        if (strncmp(buf, "default", 7) == 0) {
                if (mddev->pers)
@@ -4496,19 +4633,22 @@ array_size_store(struct mddev *mddev, const char *buf, size_t len)
                mddev->external_size = 0;
        } else {
                if (strict_blocks_to_sectors(buf, &sectors) < 0)
-                       return -EINVAL;
-               if (mddev->pers && mddev->pers->size(mddev, 0, 0) < sectors)
-                       return -E2BIG;
-
-               mddev->external_size = 1;
+                       err = -EINVAL;
+               else if (mddev->pers && mddev->pers->size(mddev, 0, 0) < sectors)
+                       err = -E2BIG;
+               else
+                       mddev->external_size = 1;
        }
 
-       mddev->array_sectors = sectors;
-       if (mddev->pers) {
-               set_capacity(mddev->gendisk, mddev->array_sectors);
-               revalidate_disk(mddev->gendisk);
+       if (!err) {
+               mddev->array_sectors = sectors;
+               if (mddev->pers) {
+                       set_capacity(mddev->gendisk, mddev->array_sectors);
+                       revalidate_disk(mddev->gendisk);
+               }
        }
-       return len;
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry md_array_size =
@@ -4596,13 +4736,7 @@ md_attr_store(struct kobject *kobj, struct attribute *attr,
        }
        mddev_get(mddev);
        spin_unlock(&all_mddevs_lock);
-       if (entry->store == new_dev_store)
-               flush_workqueue(md_misc_wq);
-       rv = mddev_lock(mddev);
-       if (!rv) {
-               rv = entry->store(mddev, page, length);
-               mddev_unlock(mddev);
-       }
+       rv = entry->store(mddev, page, length);
        mddev_put(mddev);
        return rv;
 }

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d5b8017..aa76865 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5400,21 +5400,25 @@ EXPORT_SYMBOL(raid5_set_cache_size);
 static ssize_t
 raid5_store_stripe_cache_size(struct mddev *mddev, const char *page, size_t len)
 {
-       struct r5conf *conf = mddev->private;
+       struct r5conf *conf;
        unsigned long new;
        int err;
 
        if (len >= PAGE_SIZE)
                return -EINVAL;
-       if (!conf)
-               return -ENODEV;
-
        if (kstrtoul(page, 10, &new))
                return -EINVAL;
-       err = raid5_set_cache_size(mddev, new);
+       err = mddev_lock(mddev);
        if (err)
                return err;
-       return len;
+       conf = mddev->private;
+       if (!conf)
+               err = -ENODEV;
+       else
+               err = raid5_set_cache_size(mddev, new);
+       mddev_unlock(mddev);
+
+       return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5438,19 +5442,27 @@ raid5_show_preread_threshold(struct mddev *mddev, char *page)
 static ssize_t
 raid5_store_preread_threshold(struct mddev *mddev, const char *page, size_t len)
 {
-       struct r5conf *conf = mddev->private;
+       struct r5conf *conf;
        unsigned long new;
+       int err;
+
        if (len >= PAGE_SIZE)
                return -EINVAL;
-       if (!conf)
-               return -ENODEV;
-
        if (kstrtoul(page, 10, &new))
                return -EINVAL;
-       if (new > conf->max_nr_stripes)
-               return -EINVAL;
-       conf->bypass_threshold = new;
-       return len;
+
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       conf = mddev->private;
+       if (!conf)
+               err = -ENODEV;
+       else if (new > conf->max_nr_stripes)
+               err = -EINVAL;
+       else
+               conf->bypass_threshold = new;
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5475,29 +5487,35 @@ raid5_show_skip_copy(struct mddev *mddev, char *page)
 static ssize_t
 raid5_store_skip_copy(struct mddev *mddev, const char *page, size_t len)
 {
-       struct r5conf *conf = mddev->private;
+       struct r5conf *conf;
        unsigned long new;
+       int err;
+
        if (len >= PAGE_SIZE)
                return -EINVAL;
-       if (!conf)
-               return -ENODEV;
-
        if (kstrtoul(page, 10, &new))
                return -EINVAL;
        new = !!new;
-       if (new == conf->skip_copy)
-               return len;
 
-       mddev_suspend(mddev);
-       conf->skip_copy = new;
-       if (new)
-               mddev->queue->backing_dev_info.capabilities |=
-                                               BDI_CAP_STABLE_WRITES;
-       else
-               mddev->queue->backing_dev_info.capabilities &=
-                                               ~BDI_CAP_STABLE_WRITES;
-       mddev_resume(mddev);
-       return len;
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       conf = mddev->private;
+       if (!conf)
+               err = -ENODEV;
+       else if (new != conf->skip_copy) {
+               mddev_suspend(mddev);
+               conf->skip_copy = new;
+               if (new)
+                       mddev->queue->backing_dev_info.capabilities |=
+                               BDI_CAP_STABLE_WRITES;
+               else
+                       mddev->queue->backing_dev_info.capabilities &=
+                               ~BDI_CAP_STABLE_WRITES;
+               mddev_resume(mddev);
+       }
+       mddev_unlock(mddev);
+       return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5538,7 +5556,7 @@ static int alloc_thread_groups(struct r5conf *conf, int cnt,
 static ssize_t
 raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 {
-       struct r5conf *conf = mddev->private;
+       struct r5conf *conf;
        unsigned long new;
        int err;
        struct r5worker_group *new_groups, *old_groups;
@@ -5546,41 +5564,41 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 
        if (len >= PAGE_SIZE)
                return -EINVAL;
-       if (!conf)
-               return -ENODEV;
-
        if (kstrtoul(page, 10, &new))
                return -EINVAL;
 
-       if (new == conf->worker_cnt_per_group)
-               return len;
-
-       mddev_suspend(mddev);
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+       conf = mddev->private;
+       if (!conf)
+               err = -ENODEV;
+       else if (new != conf->worker_cnt_per_group) {
+               mddev_suspend(mddev);
 
-       old_groups = conf->worker_groups;
-       if (old_groups)
-               flush_workqueue(raid5_wq);
+               old_groups = conf->worker_groups;
+               if (old_groups)
+                       flush_workqueue(raid5_wq);
 
-       err = alloc_thread_groups(conf, new,
-                                 &group_cnt, &worker_cnt_per_group,
-                                 &new_groups);
-       if (!err) {
-               spin_lock_irq(&conf->device_lock);
-               conf->group_cnt = group_cnt;
-               conf->worker_cnt_per_group = worker_cnt_per_group;
-               conf->worker_groups = new_groups;
-               spin_unlock_irq(&conf->device_lock);
+               err = alloc_thread_groups(conf, new,
+                                         &group_cnt, &worker_cnt_per_group,
+                                         &new_groups);
+               if (!err) {
+                       spin_lock_irq(&conf->device_lock);
+                       conf->group_cnt = group_cnt;
+                       conf->worker_cnt_per_group = worker_cnt_per_group;
+                       conf->worker_groups = new_groups;
+                       spin_unlock_irq(&conf->device_lock);
 
-               if (old_groups)
-                       kfree(old_groups[0].workers);
-               kfree(old_groups);
+                       if (old_groups)
+                               kfree(old_groups[0].workers);
+                       kfree(old_groups);
+               }
+               mddev_resume(mddev);
        }
+       mddev_unlock(mddev);
 
-       mddev_resume(mddev);
-
-       if (err)
-               return err;
-       return len;
+       return err ?: len;
 }
 
 static struct md_sysfs_entry