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block: fix synchronization and limit check in blk_alloc_devt()

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idr allocation in blk_alloc_devt() wasn't synchronized against lookup
and removal, and its limit check was off by one - 1 << MINORBITS is
the number of minors allowed, not the maximum allowed minor.

Add locking and rename MAX_EXT_DEVT to NR_EXT_DEVT and fix limit
checking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tejun Heo 2013-02-27 17:03:56 -08:00 committed by Linus Torvalds
parent d5c7409f79
commit ce23bba842
1 changed files with 5 additions and 8 deletions
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13
block/genhd.c
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@ -26,7 +26,7 @@ static DEFINE_MUTEX(block_class_lock);
struct kobject *block_depr;
/* for extended dynamic devt allocation, currently only one major is used */
#define MAX_EXT_DEVT (1 << MINORBITS)
#define NR_EXT_DEVT (1 << MINORBITS)
/* For extended devt allocation. ext_devt_mutex prevents look up
* results from going away underneath its user.
@ -425,19 +425,16 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
return -ENOMEM;
mutex_lock(&ext_devt_mutex);
rc = idr_get_new(&ext_devt_idr, part, &idx);
if (!rc && idx >= NR_EXT_DEVT) {
idr_remove(&ext_devt_idr, idx);
rc = -EBUSY;
}
mutex_unlock(&ext_devt_mutex);
} while (rc == -EAGAIN);
if (rc)
return rc;
if (idx > MAX_EXT_DEVT) {
mutex_lock(&ext_devt_mutex);
idr_remove(&ext_devt_idr, idx);
mutex_unlock(&ext_devt_mutex);
return -EBUSY;
}
*devt = MKDEV(BLOCK_EXT_MAJOR, blk_mangle_minor(idx));
return 0;
}