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block: acquire q->limits_lock while reading sysfs attributes

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There're few sysfs attributes(RW) whose store method is protected
with q->limits_lock, however the corresponding show method of these
attributes run holding q->sysfs_lock and that doesn't make sense
as ideally the show method of these attributes should also run
holding q->limits_lock instead of q->sysfs_lock. Hence update the
show method of these sysfs attributes so that reading of these
attributes acquire q->limits_lock instead of q->sysfs_lock.

Similarly, there're few sysfs attributes(RO) whose show method is
currently protected with q->sysfs_lock however updates to these
attributes could occur using atomic limit update APIs such as queue_
limits_start_update() and queue_limits_commit_update() which run
holding q->limits_lock. So that means that reading these attributes
holding q->sysfs_lock doesn't make sense. Hence update the show method
of these sysfs attributes(RO) such that they run with holding q->
limits_lock instead of q->sysfs_lock.

We have defined a new macro QUEUE_LIM_RO_ENTRY() which uses new ->show_
limit() method and it runs holding q->limits_lock. All existing sysfs
attributes(RO) which needs protection using q->limits_lock while
reading have been now updated to use this new macro for initialization.

Also, the existing QUEUE_LIM_RW_ENTRY() is updated to use new ->show_
limit() method for reading attributes instead of existing ->show()
method. As ->show_limit() runs holding q->limits_lock, the existing
sysfs attributes(RW) requiring protection are now inherently protected
using q->limits_lock instead of q->sysfs_lock.

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/20250304102551.2533767-2-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Nilay Shroff 2025-03-04 15:52:30 +05:30 committed by Jens Axboe
parent d301f164c3
commit 6e51a1279c
1 changed files with 65 additions and 37 deletions
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102
block/blk-sysfs.c
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@ -23,9 +23,12 @@
struct queue_sysfs_entry {
struct attribute attr;
ssize_t (*show)(struct gendisk *disk, char *page);
ssize_t (*show_limit)(struct gendisk *disk, char *page);
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);
};
@ -412,10 +415,16 @@ static struct queue_sysfs_entry _prefix##_entry = { \
.store = _prefix##_store, \
};
#define QUEUE_LIM_RO_ENTRY(_prefix, _name) \
static struct queue_sysfs_entry _prefix##_entry = { \
.attr = { .name = _name, .mode = 0444 }, \
.show_limit = _prefix##_show, \
}
#define QUEUE_LIM_RW_ENTRY(_prefix, _name) \
static struct queue_sysfs_entry _prefix##_entry = { \
.attr = { .name = _name, .mode = 0644 }, \
.show = _prefix##_show, \
.show_limit = _prefix##_show, \
.store_limit = _prefix##_store, \
}
@ -430,39 +439,39 @@ static struct queue_sysfs_entry _prefix##_entry = { \
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");
QUEUE_RO_ENTRY(queue_max_hw_sectors, "max_hw_sectors_kb");
QUEUE_RO_ENTRY(queue_max_segments, "max_segments");
QUEUE_RO_ENTRY(queue_max_integrity_segments, "max_integrity_segments");
QUEUE_RO_ENTRY(queue_max_segment_size, "max_segment_size");
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_RO_ENTRY(queue_logical_block_size, "logical_block_size");
QUEUE_RO_ENTRY(queue_physical_block_size, "physical_block_size");
QUEUE_RO_ENTRY(queue_chunk_sectors, "chunk_sectors");
QUEUE_RO_ENTRY(queue_io_min, "minimum_io_size");
QUEUE_RO_ENTRY(queue_io_opt, "optimal_io_size");
QUEUE_LIM_RO_ENTRY(queue_logical_block_size, "logical_block_size");
QUEUE_LIM_RO_ENTRY(queue_physical_block_size, "physical_block_size");
QUEUE_LIM_RO_ENTRY(queue_chunk_sectors, "chunk_sectors");
QUEUE_LIM_RO_ENTRY(queue_io_min, "minimum_io_size");
QUEUE_LIM_RO_ENTRY(queue_io_opt, "optimal_io_size");
QUEUE_RO_ENTRY(queue_max_discard_segments, "max_discard_segments");
QUEUE_RO_ENTRY(queue_discard_granularity, "discard_granularity");
QUEUE_RO_ENTRY(queue_max_hw_discard_sectors, "discard_max_hw_bytes");
QUEUE_LIM_RO_ENTRY(queue_max_discard_segments, "max_discard_segments");
QUEUE_LIM_RO_ENTRY(queue_discard_granularity, "discard_granularity");
QUEUE_LIM_RO_ENTRY(queue_max_hw_discard_sectors, "discard_max_hw_bytes");
QUEUE_LIM_RW_ENTRY(queue_max_discard_sectors, "discard_max_bytes");
QUEUE_RO_ENTRY(queue_discard_zeroes_data, "discard_zeroes_data");
QUEUE_RO_ENTRY(queue_atomic_write_max_sectors, "atomic_write_max_bytes");
QUEUE_RO_ENTRY(queue_atomic_write_boundary_sectors,
QUEUE_LIM_RO_ENTRY(queue_atomic_write_max_sectors, "atomic_write_max_bytes");
QUEUE_LIM_RO_ENTRY(queue_atomic_write_boundary_sectors,
"atomic_write_boundary_bytes");
QUEUE_RO_ENTRY(queue_atomic_write_unit_max, "atomic_write_unit_max_bytes");
QUEUE_RO_ENTRY(queue_atomic_write_unit_min, "atomic_write_unit_min_bytes");
QUEUE_LIM_RO_ENTRY(queue_atomic_write_unit_max, "atomic_write_unit_max_bytes");
QUEUE_LIM_RO_ENTRY(queue_atomic_write_unit_min, "atomic_write_unit_min_bytes");
QUEUE_RO_ENTRY(queue_write_same_max, "write_same_max_bytes");
QUEUE_RO_ENTRY(queue_max_write_zeroes_sectors, "write_zeroes_max_bytes");
QUEUE_RO_ENTRY(queue_max_zone_append_sectors, "zone_append_max_bytes");
QUEUE_RO_ENTRY(queue_zone_write_granularity, "zone_write_granularity");
QUEUE_LIM_RO_ENTRY(queue_max_write_zeroes_sectors, "write_zeroes_max_bytes");
QUEUE_LIM_RO_ENTRY(queue_max_zone_append_sectors, "zone_append_max_bytes");
QUEUE_LIM_RO_ENTRY(queue_zone_write_granularity, "zone_write_granularity");
QUEUE_RO_ENTRY(queue_zoned, "zoned");
QUEUE_LIM_RO_ENTRY(queue_zoned, "zoned");
QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
QUEUE_LIM_RO_ENTRY(queue_max_open_zones, "max_open_zones");
QUEUE_LIM_RO_ENTRY(queue_max_active_zones, "max_active_zones");
QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
QUEUE_LIM_RW_ENTRY(queue_iostats_passthrough, "iostats_passthrough");
@ -470,16 +479,16 @@ QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
QUEUE_RW_ENTRY(queue_poll, "io_poll");
QUEUE_RW_ENTRY(queue_poll_delay, "io_poll_delay");
QUEUE_LIM_RW_ENTRY(queue_wc, "write_cache");
QUEUE_RO_ENTRY(queue_fua, "fua");
QUEUE_RO_ENTRY(queue_dax, "dax");
QUEUE_LIM_RO_ENTRY(queue_fua, "fua");
QUEUE_LIM_RO_ENTRY(queue_dax, "dax");
QUEUE_RW_ENTRY(queue_io_timeout, "io_timeout");
QUEUE_RO_ENTRY(queue_virt_boundary_mask, "virt_boundary_mask");
QUEUE_RO_ENTRY(queue_dma_alignment, "dma_alignment");
QUEUE_LIM_RO_ENTRY(queue_virt_boundary_mask, "virt_boundary_mask");
QUEUE_LIM_RO_ENTRY(queue_dma_alignment, "dma_alignment");
/* legacy alias for logical_block_size: */
static struct queue_sysfs_entry queue_hw_sector_size_entry = {
.attr = {.name = "hw_sector_size", .mode = 0444 },
.show = queue_logical_block_size_show,
.attr = {.name = "hw_sector_size", .mode = 0444 },
.show_limit = queue_logical_block_size_show,
};
QUEUE_LIM_RW_ENTRY(queue_rotational, "rotational");
@ -561,7 +570,9 @@ QUEUE_RW_ENTRY(queue_wb_lat, "wbt_lat_usec");
/* Common attributes for bio-based and request-based queues. */
static struct attribute *queue_attrs[] = {
&queue_ra_entry.attr,
/*
* Attributes which are protected with q->limits_lock.
*/
&queue_max_hw_sectors_entry.attr,
&queue_max_sectors_entry.attr,
&queue_max_segments_entry.attr,
@ -577,37 +588,46 @@ static struct attribute *queue_attrs[] = {
&queue_discard_granularity_entry.attr,
&queue_max_discard_sectors_entry.attr,
&queue_max_hw_discard_sectors_entry.attr,
&queue_discard_zeroes_data_entry.attr,
&queue_atomic_write_max_sectors_entry.attr,
&queue_atomic_write_boundary_sectors_entry.attr,
&queue_atomic_write_unit_min_entry.attr,
&queue_atomic_write_unit_max_entry.attr,
&queue_write_same_max_entry.attr,
&queue_max_write_zeroes_sectors_entry.attr,
&queue_max_zone_append_sectors_entry.attr,
&queue_zone_write_granularity_entry.attr,
&queue_rotational_entry.attr,
&queue_zoned_entry.attr,
&queue_nr_zones_entry.attr,
&queue_max_open_zones_entry.attr,
&queue_max_active_zones_entry.attr,
&queue_nomerges_entry.attr,
&queue_iostats_passthrough_entry.attr,
&queue_iostats_entry.attr,
&queue_stable_writes_entry.attr,
&queue_add_random_entry.attr,
&queue_poll_entry.attr,
&queue_wc_entry.attr,
&queue_fua_entry.attr,
&queue_dax_entry.attr,
&queue_poll_delay_entry.attr,
&queue_virt_boundary_mask_entry.attr,
&queue_dma_alignment_entry.attr,
/*
* Attributes which are protected with q->sysfs_lock.
*/
&queue_ra_entry.attr,
&queue_discard_zeroes_data_entry.attr,
&queue_write_same_max_entry.attr,
&queue_nr_zones_entry.attr,
&queue_nomerges_entry.attr,
&queue_poll_entry.attr,
&queue_poll_delay_entry.attr,
NULL,
};
/* Request-based queue attributes that are not relevant for bio-based queues. */
static struct attribute *blk_mq_queue_attrs[] = {
/*
* Attributes which are protected with q->sysfs_lock.
*/
&queue_requests_entry.attr,
&elv_iosched_entry.attr,
&queue_rq_affinity_entry.attr,
@ -666,8 +686,16 @@ queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
struct gendisk *disk = container_of(kobj, struct gendisk, queue_kobj);
ssize_t res;
if (!entry->show)
if (!entry->show && !entry->show_limit)
return -EIO;
if (entry->show_limit) {
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);