blk-mq-debug: Make show() operations interruptible

Allow users to interrupt show operations instead of making a user
space process unkillable if ownership of q->sysfs_lock cannot be
obtained.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 0119ec533824e579de1c79a23dd6466743292c6b..54b2f484eab45a86808beb14135dff99b113934d 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -178,13 +178,17 @@ static int hctx_tags_show(struct seq_file *m, void *v)
 {
        struct blk_mq_hw_ctx *hctx = m->private;
        struct request_queue *q = hctx->queue;
+       int res;
 
-       mutex_lock(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->sysfs_lock);
+       if (res)
+               goto out;
        if (hctx->tags)
                blk_mq_debugfs_tags_show(m, hctx->tags);
        mutex_unlock(&q->sysfs_lock);
 
-       return 0;
+out:
+       return res;
 }
 
 static int hctx_tags_open(struct inode *inode, struct file *file)
@@ -203,12 +207,17 @@ static int hctx_tags_bitmap_show(struct seq_file *m, void *v)
 {
        struct blk_mq_hw_ctx *hctx = m->private;
        struct request_queue *q = hctx->queue;
+       int res;
 
-       mutex_lock(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->sysfs_lock);
+       if (res)
+               goto out;
        if (hctx->tags)
                sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m);
        mutex_unlock(&q->sysfs_lock);
-       return 0;
+
+out:
+       return res;
 }
 
 static int hctx_tags_bitmap_open(struct inode *inode, struct file *file)
@@ -227,13 +236,17 @@ static int hctx_sched_tags_show(struct seq_file *m, void *v)
 {
        struct blk_mq_hw_ctx *hctx = m->private;
        struct request_queue *q = hctx->queue;
+       int res;
 
-       mutex_lock(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->sysfs_lock);
+       if (res)
+               goto out;
        if (hctx->sched_tags)
                blk_mq_debugfs_tags_show(m, hctx->sched_tags);
        mutex_unlock(&q->sysfs_lock);
 
-       return 0;
+out:
+       return res;
 }
 
 static int hctx_sched_tags_open(struct inode *inode, struct file *file)
@@ -252,12 +265,17 @@ static int hctx_sched_tags_bitmap_show(struct seq_file *m, void *v)
 {
        struct blk_mq_hw_ctx *hctx = m->private;
        struct request_queue *q = hctx->queue;
+       int res;
 
-       mutex_lock(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->sysfs_lock);
+       if (res)
+               goto out;
        if (hctx->sched_tags)
                sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m);
        mutex_unlock(&q->sysfs_lock);
-       return 0;
+
+out:
+       return res;
 }
 
 static int hctx_sched_tags_bitmap_open(struct inode *inode, struct file *file)