block: move q->sysfs_lock and queue-freeze under show/store method

In preparation to further simplify and group sysfs attributes which
don't require locking or require some form of locking other than q->
limits_lock, move acquire/release of q->sysfs_lock and queue freeze/
unfreeze under each attributes' respective show/store method.

While we are at it, also remove ->load_module() as it's used to load
the module before queue is freezed. Now as we moved queue-freeze under
->store(), we could load module directly from the attributes' store
method before we actually start freezing the queue. Currently, the
->load_module() is only used by "scheduler" attribute, so we now load
the relevant elevator module before we start freezing the queue in
elv_iosched_store().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304102551.2533767-3-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index eba5121690af16451cd12db8684589180cc5daed..4700ee168ed5ebc33335b700082a85d7856d5f53 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -28,8 +28,6 @@ struct queue_sysfs_entry {
        ssize_t (*store)(struct gendisk *disk, const char *page, size_t count);
        int (*store_limit)(struct gendisk *disk, const char *page,
                        size_t count, struct queue_limits *lim);
-
-       void (*load_module)(struct gendisk *disk, const char *page, size_t count);
 };
 
 static ssize_t
@@ -55,7 +53,12 @@ queue_var_store(unsigned long *var, const char *page, size_t count)
 
 static ssize_t queue_requests_show(struct gendisk *disk, char *page)
 {
-       return queue_var_show(disk->queue->nr_requests, page);
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       ret = queue_var_show(disk->queue->nr_requests, page);
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t
@@ -63,27 +66,38 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count)
 {
        unsigned long nr;
        int ret, err;
+       unsigned int memflags;
+       struct request_queue *q = disk->queue;
 
-       if (!queue_is_mq(disk->queue))
+       if (!queue_is_mq(q))
                return -EINVAL;
 
        ret = queue_var_store(&nr, page, count);
        if (ret < 0)
                return ret;
 
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
        if (nr < BLKDEV_MIN_RQ)
                nr = BLKDEV_MIN_RQ;
 
        err = blk_mq_update_nr_requests(disk->queue, nr);
        if (err)
-               return err;
-
+               ret = err;
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
        return ret;
 }
 
 static ssize_t queue_ra_show(struct gendisk *disk, char *page)
 {
-       return queue_var_show(disk->bdi->ra_pages << (PAGE_SHIFT - 10), page);
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       ret = queue_var_show(disk->bdi->ra_pages << (PAGE_SHIFT - 10), page);
+       mutex_unlock(&disk->queue->sysfs_lock);
+
+       return ret;
 }
 
 static ssize_t
@@ -91,11 +105,19 @@ queue_ra_store(struct gendisk *disk, const char *page, size_t count)
 {
        unsigned long ra_kb;
        ssize_t ret;
+       unsigned int memflags;
+       struct request_queue *q = disk->queue;
 
        ret = queue_var_store(&ra_kb, page, count);
        if (ret < 0)
                return ret;
+
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
        disk->bdi->ra_pages = ra_kb >> (PAGE_SHIFT - 10);
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
+
        return ret;
 }
 
@@ -150,7 +172,12 @@ QUEUE_SYSFS_LIMIT_SHOW_SECTORS_TO_KB(max_hw_sectors)
 #define QUEUE_SYSFS_SHOW_CONST(_name, _val)                            \
 static ssize_t queue_##_name##_show(struct gendisk *disk, char *page)  \
 {                                                                      \
-       return sysfs_emit(page, "%d\n", _val);                          \
+       ssize_t ret;                                                    \
+                                                                       \
+       mutex_lock(&disk->queue->sysfs_lock);                           \
+       ret = sysfs_emit(page, "%d\n", _val);                           \
+       mutex_unlock(&disk->queue->sysfs_lock);                         \
+       return ret;                                                     \
 }
 
 /* deprecated fields */
@@ -239,10 +266,17 @@ QUEUE_SYSFS_FEATURE_SHOW(dax, BLK_FEAT_DAX);
 
 static ssize_t queue_poll_show(struct gendisk *disk, char *page)
 {
-       if (queue_is_mq(disk->queue))
-               return sysfs_emit(page, "%u\n", blk_mq_can_poll(disk->queue));
-       return sysfs_emit(page, "%u\n",
-               !!(disk->queue->limits.features & BLK_FEAT_POLL));
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       if (queue_is_mq(disk->queue)) {
+               ret = sysfs_emit(page, "%u\n", blk_mq_can_poll(disk->queue));
+       } else {
+               ret = sysfs_emit(page, "%u\n",
+                       !!(disk->queue->limits.features & BLK_FEAT_POLL));
+       }
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t queue_zoned_show(struct gendisk *disk, char *page)
@@ -254,7 +288,12 @@ static ssize_t queue_zoned_show(struct gendisk *disk, char *page)
 
 static ssize_t queue_nr_zones_show(struct gendisk *disk, char *page)
 {
-       return queue_var_show(disk_nr_zones(disk), page);
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       ret = queue_var_show(disk_nr_zones(disk), page);
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t queue_iostats_passthrough_show(struct gendisk *disk, char *page)
@@ -281,35 +320,51 @@ static int queue_iostats_passthrough_store(struct gendisk *disk,
 
 static ssize_t queue_nomerges_show(struct gendisk *disk, char *page)
 {
-       return queue_var_show((blk_queue_nomerges(disk->queue) << 1) |
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       ret = queue_var_show((blk_queue_nomerges(disk->queue) << 1) |
                               blk_queue_noxmerges(disk->queue), page);
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t queue_nomerges_store(struct gendisk *disk, const char *page,
                                    size_t count)
 {
        unsigned long nm;
+       unsigned int memflags;
+       struct request_queue *q = disk->queue;
        ssize_t ret = queue_var_store(&nm, page, count);
 
        if (ret < 0)
                return ret;
 
-       blk_queue_flag_clear(QUEUE_FLAG_NOMERGES, disk->queue);
-       blk_queue_flag_clear(QUEUE_FLAG_NOXMERGES, disk->queue);
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
+       blk_queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
+       blk_queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
        if (nm == 2)
-               blk_queue_flag_set(QUEUE_FLAG_NOMERGES, disk->queue);
+               blk_queue_flag_set(QUEUE_FLAG_NOMERGES, q);
        else if (nm)
-               blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, disk->queue);
+               blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
 
        return ret;
 }
 
 static ssize_t queue_rq_affinity_show(struct gendisk *disk, char *page)
 {
-       bool set = test_bit(QUEUE_FLAG_SAME_COMP, &disk->queue->queue_flags);
-       bool force = test_bit(QUEUE_FLAG_SAME_FORCE, &disk->queue->queue_flags);
+       ssize_t ret;
+       bool set, force;
 
-       return queue_var_show(set << force, page);
+       mutex_lock(&disk->queue->sysfs_lock);
+       set = test_bit(QUEUE_FLAG_SAME_COMP, &disk->queue->queue_flags);
+       force = test_bit(QUEUE_FLAG_SAME_FORCE, &disk->queue->queue_flags);
+       ret = queue_var_show(set << force, page);
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t
@@ -319,11 +374,14 @@ queue_rq_affinity_store(struct gendisk *disk, const char *page, size_t count)
 #ifdef CONFIG_SMP
        struct request_queue *q = disk->queue;
        unsigned long val;
+       unsigned int memflags;
 
        ret = queue_var_store(&val, page, count);
        if (ret < 0)
                return ret;
 
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
        if (val == 2) {
                blk_queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
                blk_queue_flag_set(QUEUE_FLAG_SAME_FORCE, q);
@@ -334,6 +392,8 @@ queue_rq_affinity_store(struct gendisk *disk, const char *page, size_t count)
                blk_queue_flag_clear(QUEUE_FLAG_SAME_COMP, q);
                blk_queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
        }
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
 #endif
        return ret;
 }
@@ -347,29 +407,52 @@ static ssize_t queue_poll_delay_store(struct gendisk *disk, const char *page,
 static ssize_t queue_poll_store(struct gendisk *disk, const char *page,
                                size_t count)
 {
-       if (!(disk->queue->limits.features & BLK_FEAT_POLL))
-               return -EINVAL;
+       unsigned int memflags;
+       ssize_t ret = count;
+       struct request_queue *q = disk->queue;
+
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
+       if (!(q->limits.features & BLK_FEAT_POLL)) {
+               ret = -EINVAL;
+               goto out;
+       }
        pr_info_ratelimited("writes to the poll attribute are ignored.\n");
        pr_info_ratelimited("please use driver specific parameters instead.\n");
-       return count;
+out:
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
+
+       return ret;
 }
 
 static ssize_t queue_io_timeout_show(struct gendisk *disk, char *page)
 {
-       return sysfs_emit(page, "%u\n", jiffies_to_msecs(disk->queue->rq_timeout));
+       ssize_t ret;
+
+       mutex_lock(&disk->queue->sysfs_lock);
+       ret = sysfs_emit(page, "%u\n",
+                       jiffies_to_msecs(disk->queue->rq_timeout));
+       mutex_unlock(&disk->queue->sysfs_lock);
+       return ret;
 }
 
 static ssize_t queue_io_timeout_store(struct gendisk *disk, const char *page,
                                  size_t count)
 {
-       unsigned int val;
+       unsigned int val, memflags;
        int err;
+       struct request_queue *q = disk->queue;
 
        err = kstrtou32(page, 10, &val);
        if (err || val == 0)
                return -EINVAL;
 
-       blk_queue_rq_timeout(disk->queue, msecs_to_jiffies(val));
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
+       blk_queue_rq_timeout(q, msecs_to_jiffies(val));
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
 
        return count;
 }
@@ -428,14 +511,6 @@ static struct queue_sysfs_entry _prefix##_entry = {        \
        .store_limit    = _prefix##_store,                      \
 }
 
-#define QUEUE_RW_LOAD_MODULE_ENTRY(_prefix, _name)             \
-static struct queue_sysfs_entry _prefix##_entry = {            \
-       .attr           = { .name = _name, .mode = 0644 },      \
-       .show           = _prefix##_show,                       \
-       .load_module    = _prefix##_load_module,                \
-       .store          = _prefix##_store,                      \
-}
-
 QUEUE_RW_ENTRY(queue_requests, "nr_requests");
 QUEUE_RW_ENTRY(queue_ra, "read_ahead_kb");
 QUEUE_LIM_RW_ENTRY(queue_max_sectors, "max_sectors_kb");
@@ -443,7 +518,7 @@ QUEUE_LIM_RO_ENTRY(queue_max_hw_sectors, "max_hw_sectors_kb");
 QUEUE_LIM_RO_ENTRY(queue_max_segments, "max_segments");
 QUEUE_LIM_RO_ENTRY(queue_max_integrity_segments, "max_integrity_segments");
 QUEUE_LIM_RO_ENTRY(queue_max_segment_size, "max_segment_size");
-QUEUE_RW_LOAD_MODULE_ENTRY(elv_iosched, "scheduler");
+QUEUE_RW_ENTRY(elv_iosched, "scheduler");
 
 QUEUE_LIM_RO_ENTRY(queue_logical_block_size, "logical_block_size");
 QUEUE_LIM_RO_ENTRY(queue_physical_block_size, "physical_block_size");
@@ -512,14 +587,24 @@ static ssize_t queue_var_store64(s64 *var, const char *page)
 
 static ssize_t queue_wb_lat_show(struct gendisk *disk, char *page)
 {
-       if (!wbt_rq_qos(disk->queue))
-               return -EINVAL;
+       ssize_t ret;
+       struct request_queue *q = disk->queue;
 
-       if (wbt_disabled(disk->queue))
-               return sysfs_emit(page, "0\n");
+       mutex_lock(&q->sysfs_lock);
+       if (!wbt_rq_qos(q)) {
+               ret = -EINVAL;
+               goto out;
+       }
 
-       return sysfs_emit(page, "%llu\n",
-               div_u64(wbt_get_min_lat(disk->queue), 1000));
+       if (wbt_disabled(q)) {
+               ret = sysfs_emit(page, "0\n");
+               goto out;
+       }
+
+       ret = sysfs_emit(page, "%llu\n", div_u64(wbt_get_min_lat(q), 1000));
+out:
+       mutex_unlock(&q->sysfs_lock);
+       return ret;
 }
 
 static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
@@ -529,6 +614,7 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
        struct rq_qos *rqos;
        ssize_t ret;
        s64 val;
+       unsigned int memflags;
 
        ret = queue_var_store64(&val, page);
        if (ret < 0)
@@ -536,20 +622,24 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
        if (val < -1)
                return -EINVAL;
 
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
+
        rqos = wbt_rq_qos(q);
        if (!rqos) {
                ret = wbt_init(disk);
                if (ret)
-                       return ret;
+                       goto out;
        }
 
+       ret = count;
        if (val == -1)
                val = wbt_default_latency_nsec(q);
        else if (val >= 0)
                val *= 1000ULL;
 
        if (wbt_get_min_lat(q) == val)
-               return count;
+               goto out;
 
        /*
         * Ensure that the queue is idled, in case the latency update
@@ -561,8 +651,11 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
        wbt_set_min_lat(q, val);
 
        blk_mq_unquiesce_queue(q);
+out:
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
 
-       return count;
+       return ret;
 }
 
 QUEUE_RW_ENTRY(queue_wb_lat, "wbt_lat_usec");
@@ -684,22 +777,20 @@ queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 {
        struct queue_sysfs_entry *entry = to_queue(attr);
        struct gendisk *disk = container_of(kobj, struct gendisk, queue_kobj);
-       ssize_t res;
 
        if (!entry->show && !entry->show_limit)
                return -EIO;
 
        if (entry->show_limit) {
+               ssize_t res;
+
                mutex_lock(&disk->queue->limits_lock);
                res = entry->show_limit(disk, page);
                mutex_unlock(&disk->queue->limits_lock);
                return res;
        }
 
-       mutex_lock(&disk->queue->sysfs_lock);
-       res = entry->show(disk, page);
-       mutex_unlock(&disk->queue->sysfs_lock);
-       return res;
+       return entry->show(disk, page);
 }
 
 static ssize_t
@@ -709,21 +800,13 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
        struct queue_sysfs_entry *entry = to_queue(attr);
        struct gendisk *disk = container_of(kobj, struct gendisk, queue_kobj);
        struct request_queue *q = disk->queue;
-       unsigned int memflags;
-       ssize_t res;
 
        if (!entry->store_limit && !entry->store)
                return -EIO;
 
-       /*
-        * If the attribute needs to load a module, do it before freezing the
-        * queue to ensure that the module file can be read when the request
-        * queue is the one for the device storing the module file.
-        */
-       if (entry->load_module)
-               entry->load_module(disk, page, length);
-
        if (entry->store_limit) {
+               ssize_t res;
+
                struct queue_limits lim = queue_limits_start_update(q);
 
                res = entry->store_limit(disk, page, length, &lim);
@@ -738,12 +821,7 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
                return length;
        }
 
-       mutex_lock(&q->sysfs_lock);
-       memflags = blk_mq_freeze_queue(q);
-       res = entry->store(disk, page, length);
-       blk_mq_unfreeze_queue(q, memflags);
-       mutex_unlock(&q->sysfs_lock);
-       return res;
+       return entry->store(disk, page, length);
 }
 
 static const struct sysfs_ops queue_sysfs_ops = {

diff --git a/block/elevator.c b/block/elevator.c
index cd2ce492160100e90326ae1dceac6013e624f5d5..041f1d983bc7647e80152188d88f9173f78763c5 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -723,11 +723,24 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
 {
        char elevator_name[ELV_NAME_MAX];
        int ret;
+       unsigned int memflags;
+       struct request_queue *q = disk->queue;
 
+       /*
+        * If the attribute needs to load a module, do it before freezing the
+        * queue to ensure that the module file can be read when the request
+        * queue is the one for the device storing the module file.
+        */
+       elv_iosched_load_module(disk, buf, count);
        strscpy(elevator_name, buf, sizeof(elevator_name));
-       ret = elevator_change(disk->queue, strstrip(elevator_name));
+
+       mutex_lock(&q->sysfs_lock);
+       memflags = blk_mq_freeze_queue(q);
+       ret = elevator_change(q, strstrip(elevator_name));
        if (!ret)
-               return count;
+               ret = count;
+       blk_mq_unfreeze_queue(q, memflags);
+       mutex_unlock(&q->sysfs_lock);
        return ret;
 }
 
@@ -738,6 +751,7 @@ ssize_t elv_iosched_show(struct gendisk *disk, char *name)
        struct elevator_type *cur = NULL, *e;
        int len = 0;
 
+       mutex_lock(&q->sysfs_lock);
        if (!q->elevator) {
                len += sprintf(name+len, "[none] ");
        } else {
@@ -755,6 +769,8 @@ ssize_t elv_iosched_show(struct gendisk *disk, char *name)
        spin_unlock(&elv_list_lock);
 
        len += sprintf(name+len, "\n");
+       mutex_unlock(&q->sysfs_lock);
+
        return len;
 }