Re: [PATCHv3 1/7] block: acquire q->limits_lock while reading sysfs attributes
From: Hannes Reinecke <hare@suse.de>
Date: 2025-02-25 07:38:26
On 2/24/25 14:30, Nilay Shroff wrote:
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> Signed-off-by: Nilay Shroff <redacted> --- block/blk-sysfs.c | 102 +++++++++++++++++++++++++++++----------------- 1 file changed, 65 insertions(+), 37 deletions(-)
Reviewed-by: Hannes Reinecke <hare@suse.de> Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich