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Tue, 7 Jan 2025 07:51:15 +0000 (GMT) Message-ID: Date: Tue, 7 Jan 2025 13:21:14 +0530 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/8] block: add a store_limit operations for sysfs entries To: Ming Lei , Christoph Hellwig Cc: Jens Axboe , Damien Le Moal , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, nbd@other.debian.org, linux-scsi@vger.kernel.org, usb-storage@lists.one-eyed-alien.net References: <20250107063120.1011593-1-hch@lst.de> <20250107063120.1011593-5-hch@lst.de> Content-Language: en-US From: Nilay Shroff In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: b86AiZTCrZgm7RWtYs4Ji68WHGqpZhiQ X-Proofpoint-ORIG-GUID: b86AiZTCrZgm7RWtYs4Ji68WHGqpZhiQ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 priorityscore=1501 clxscore=1015 lowpriorityscore=0 spamscore=0 suspectscore=0 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501070061 On 1/7/25 12:55 PM, Ming Lei wrote: > On Tue, Jan 07, 2025 at 07:30:36AM +0100, Christoph Hellwig wrote: >> De-duplicate the code for updating queue limits by adding a store_limit >> method that allows having common code handle the actual queue limits >> update. >> >> Note that this is a pure refactoring patch and does not address the >> existing freeze vs limits lock order problem in the refactored code, >> which will be addressed next. >> >> Signed-off-by: Christoph Hellwig >> --- >> block/blk-sysfs.c | 128 ++++++++++++++++++++++------------------------ >> 1 file changed, 61 insertions(+), 67 deletions(-) >> >> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c >> index 767598e719ab..8d69315e986d 100644 >> --- a/block/blk-sysfs.c >> +++ b/block/blk-sysfs.c >> @@ -24,6 +24,8 @@ struct queue_sysfs_entry { >> struct attribute attr; >> ssize_t (*show)(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); >> }; >> >> @@ -153,13 +155,11 @@ QUEUE_SYSFS_SHOW_CONST(discard_zeroes_data, 0) >> QUEUE_SYSFS_SHOW_CONST(write_same_max, 0) >> QUEUE_SYSFS_SHOW_CONST(poll_delay, -1) >> >> -static ssize_t queue_max_discard_sectors_store(struct gendisk *disk, >> - const char *page, size_t count) >> +static int queue_max_discard_sectors_store(struct gendisk *disk, >> + const char *page, size_t count, struct queue_limits *lim) >> { >> unsigned long max_discard_bytes; >> - struct queue_limits lim; >> ssize_t ret; >> - int err; >> >> ret = queue_var_store(&max_discard_bytes, page, count); >> if (ret < 0) >> @@ -171,38 +171,28 @@ static ssize_t queue_max_discard_sectors_store(struct gendisk *disk, >> if ((max_discard_bytes >> SECTOR_SHIFT) > UINT_MAX) >> return -EINVAL; >> >> - lim = queue_limits_start_update(disk->queue); >> - lim.max_user_discard_sectors = max_discard_bytes >> SECTOR_SHIFT; >> - err = queue_limits_commit_update(disk->queue, &lim); >> - if (err) >> - return err; >> - return ret; >> + lim->max_user_discard_sectors = max_discard_bytes >> SECTOR_SHIFT; >> + return 0; >> } >> >> -static ssize_t >> -queue_max_sectors_store(struct gendisk *disk, const char *page, size_t count) >> +static int >> +queue_max_sectors_store(struct gendisk *disk, const char *page, size_t count, >> + struct queue_limits *lim) >> { >> unsigned long max_sectors_kb; >> - struct queue_limits lim; >> ssize_t ret; >> - int err; >> >> ret = queue_var_store(&max_sectors_kb, page, count); >> if (ret < 0) >> return ret; >> >> - lim = queue_limits_start_update(disk->queue); >> - lim.max_user_sectors = max_sectors_kb << 1; >> - err = queue_limits_commit_update(disk->queue, &lim); >> - if (err) >> - return err; >> - return ret; >> + lim->max_user_sectors = max_sectors_kb << 1; >> + return 0; >> } >> >> static ssize_t queue_feature_store(struct gendisk *disk, const char *page, >> - size_t count, blk_features_t feature) >> + size_t count, struct queue_limits *lim, blk_features_t feature) >> { >> - struct queue_limits lim; >> unsigned long val; >> ssize_t ret; >> >> @@ -210,15 +200,11 @@ static ssize_t queue_feature_store(struct gendisk *disk, const char *page, >> if (ret < 0) >> return ret; >> >> - lim = queue_limits_start_update(disk->queue); >> if (val) >> - lim.features |= feature; >> + lim->features |= feature; >> else >> - lim.features &= ~feature; >> - ret = queue_limits_commit_update(disk->queue, &lim); >> - if (ret) >> - return ret; >> - return count; >> + lim->features &= ~feature; >> + return 0; >> } >> >> #define QUEUE_SYSFS_FEATURE(_name, _feature) \ >> @@ -227,10 +213,10 @@ static ssize_t queue_##_name##_show(struct gendisk *disk, char *page) \ >> return sysfs_emit(page, "%u\n", \ >> !!(disk->queue->limits.features & _feature)); \ >> } \ >> -static ssize_t queue_##_name##_store(struct gendisk *disk, \ >> - const char *page, size_t count) \ >> +static int queue_##_name##_store(struct gendisk *disk, \ >> + const char *page, size_t count, struct queue_limits *lim) \ >> { \ >> - return queue_feature_store(disk, page, count, _feature); \ >> + return queue_feature_store(disk, page, count, lim, _feature); \ >> } >> >> QUEUE_SYSFS_FEATURE(rotational, BLK_FEAT_ROTATIONAL) >> @@ -266,10 +252,9 @@ static ssize_t queue_iostats_passthrough_show(struct gendisk *disk, char *page) >> return queue_var_show(!!blk_queue_passthrough_stat(disk->queue), page); >> } >> >> -static ssize_t queue_iostats_passthrough_store(struct gendisk *disk, >> - const char *page, size_t count) >> +static int queue_iostats_passthrough_store(struct gendisk *disk, >> + const char *page, size_t count, struct queue_limits *lim) >> { >> - struct queue_limits lim; >> unsigned long ios; >> ssize_t ret; >> >> @@ -277,18 +262,13 @@ static ssize_t queue_iostats_passthrough_store(struct gendisk *disk, >> if (ret < 0) >> return ret; >> >> - lim = queue_limits_start_update(disk->queue); >> if (ios) >> - lim.flags |= BLK_FLAG_IOSTATS_PASSTHROUGH; >> + lim->flags |= BLK_FLAG_IOSTATS_PASSTHROUGH; >> else >> - lim.flags &= ~BLK_FLAG_IOSTATS_PASSTHROUGH; >> - >> - ret = queue_limits_commit_update(disk->queue, &lim); >> - if (ret) >> - return ret; >> - >> - return count; >> + lim->flags &= ~BLK_FLAG_IOSTATS_PASSTHROUGH; >> + return 0; >> } >> + >> static ssize_t queue_nomerges_show(struct gendisk *disk, char *page) >> { >> return queue_var_show((blk_queue_nomerges(disk->queue) << 1) | >> @@ -391,12 +371,10 @@ static ssize_t queue_wc_show(struct gendisk *disk, char *page) >> return sysfs_emit(page, "write through\n"); >> } >> >> -static ssize_t queue_wc_store(struct gendisk *disk, const char *page, >> - size_t count) >> +static int queue_wc_store(struct gendisk *disk, const char *page, >> + size_t count, struct queue_limits *lim) >> { >> - struct queue_limits lim; >> bool disable; >> - int err; >> >> if (!strncmp(page, "write back", 10)) { >> disable = false; >> @@ -407,15 +385,11 @@ static ssize_t queue_wc_store(struct gendisk *disk, const char *page, >> return -EINVAL; >> } >> >> - lim = queue_limits_start_update(disk->queue); >> if (disable) >> - lim.flags |= BLK_FLAG_WRITE_CACHE_DISABLED; >> + lim->flags |= BLK_FLAG_WRITE_CACHE_DISABLED; >> else >> - lim.flags &= ~BLK_FLAG_WRITE_CACHE_DISABLED; >> - err = queue_limits_commit_update(disk->queue, &lim); >> - if (err) >> - return err; >> - return count; >> + lim->flags &= ~BLK_FLAG_WRITE_CACHE_DISABLED; >> + return 0; >> } >> >> #define QUEUE_RO_ENTRY(_prefix, _name) \ >> @@ -431,6 +405,13 @@ static struct queue_sysfs_entry _prefix##_entry = { \ >> .store = _prefix##_store, \ >> }; >> >> +#define QUEUE_LIM_RW_ENTRY(_prefix, _name) \ >> +static struct queue_sysfs_entry _prefix##_entry = { \ >> + .attr = { .name = _name, .mode = 0644 }, \ >> + .show = _prefix##_show, \ >> + .store_limit = _prefix##_store, \ >> +} >> + >> #define QUEUE_RW_LOAD_MODULE_ENTRY(_prefix, _name) \ >> static struct queue_sysfs_entry _prefix##_entry = { \ >> .attr = { .name = _name, .mode = 0644 }, \ >> @@ -441,7 +422,7 @@ static struct queue_sysfs_entry _prefix##_entry = { \ >> >> QUEUE_RW_ENTRY(queue_requests, "nr_requests"); >> QUEUE_RW_ENTRY(queue_ra, "read_ahead_kb"); >> -QUEUE_RW_ENTRY(queue_max_sectors, "max_sectors_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"); >> @@ -457,7 +438,7 @@ QUEUE_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_RW_ENTRY(queue_max_discard_sectors, "discard_max_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"); >> @@ -477,11 +458,11 @@ QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones"); >> QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones"); >> >> QUEUE_RW_ENTRY(queue_nomerges, "nomerges"); >> -QUEUE_RW_ENTRY(queue_iostats_passthrough, "iostats_passthrough"); >> +QUEUE_LIM_RW_ENTRY(queue_iostats_passthrough, "iostats_passthrough"); >> 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_RW_ENTRY(queue_wc, "write_cache"); >> +QUEUE_LIM_RW_ENTRY(queue_wc, "write_cache"); >> QUEUE_RO_ENTRY(queue_fua, "fua"); >> QUEUE_RO_ENTRY(queue_dax, "dax"); >> QUEUE_RW_ENTRY(queue_io_timeout, "io_timeout"); >> @@ -494,10 +475,10 @@ static struct queue_sysfs_entry queue_hw_sector_size_entry = { >> .show = queue_logical_block_size_show, >> }; >> >> -QUEUE_RW_ENTRY(queue_rotational, "rotational"); >> -QUEUE_RW_ENTRY(queue_iostats, "iostats"); >> -QUEUE_RW_ENTRY(queue_add_random, "add_random"); >> -QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes"); >> +QUEUE_LIM_RW_ENTRY(queue_rotational, "rotational"); >> +QUEUE_LIM_RW_ENTRY(queue_iostats, "iostats"); >> +QUEUE_LIM_RW_ENTRY(queue_add_random, "add_random"); >> +QUEUE_LIM_RW_ENTRY(queue_stable_writes, "stable_writes"); >> >> #ifdef CONFIG_BLK_WBT >> static ssize_t queue_var_store64(s64 *var, const char *page) >> @@ -695,7 +676,7 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr, >> struct request_queue *q = disk->queue; >> ssize_t res; >> >> - if (!entry->store) >> + if (!entry->store_limit && !entry->store) >> return -EIO; >> >> /* >> @@ -706,11 +687,24 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr, >> if (entry->load_module) >> entry->load_module(disk, page, length); >> >> - blk_mq_freeze_queue(q); >> mutex_lock(&q->sysfs_lock); >> - res = entry->store(disk, page, length); >> - mutex_unlock(&q->sysfs_lock); >> + blk_mq_freeze_queue(q); > > Order between freeze and ->sysfs_lock is changed, and it may cause new > lockdep warning because we may freeze queue first before acquiring > ->sysfs_lock in del_gendisk(). > On contrary, in elevator_disable() and elevator_switch() we acquire ->sysfs_lock first before freezing the queue. I think this is a mess and we need to fix ordering. We need to decide ordering rules. IMO, the correct order should be to acquire ->sysfs_lock before freezing queue. Likewise with this patch now we acquire ->limits_lock before freezing the queue. Thanks, --Nilay