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block: create the request_queue debugfs_dir on registration

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We were only creating the request_queue debugfs_dir only
for make_request block drivers (multiqueue), but never for
request-based block drivers. We did this as we were only
creating non-blktrace additional debugfs files on that directory
for make_request drivers. However, since blktrace *always* creates
that directory anyway, we special-case the use of that directory
on blktrace. Other than this being an eye-sore, this exposes
request-based block drivers to the same debugfs fragile
race that used to exist with make_request block drivers
where if we start adding files onto that directory we can later
run a race with a double removal of dentries on the directory
if we don't deal with this carefully on blktrace.

Instead, just simplify things by always creating the request_queue
debugfs_dir on request_queue registration. Rename the mutex also to
reflect the fact that this is used outside of the blktrace context.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Luis Chamberlain
2020-06-19 20:47:30 +00:00
committed by Jens Axboe
parent b431ef837e
commit 85e0cbbb8a
6 changed files with 39 additions and 48 deletions
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5
include/linux/blkdev.h
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@@ -528,9 +528,9 @@ struct request_queue {
unsigned int sg_timeout;
unsigned int sg_reserved_size;
int node;
struct mutex debugfs_mutex;
#ifdef CONFIG_BLK_DEV_IO_TRACE
struct blk_trace __rcu *blk_trace;
struct mutex blk_trace_mutex;
#endif
/*
* for flush operations
@@ -574,8 +574,9 @@ struct request_queue {
struct list_head tag_set_list;
struct bio_set bio_split;
#ifdef CONFIG_BLK_DEBUG_FS
struct dentry *debugfs_dir;
#ifdef CONFIG_BLK_DEBUG_FS
struct dentry *sched_debugfs_dir;
struct dentry *rqos_debugfs_dir;
#endif