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Message-ID: <4BBC55DD.2010201@kernel.org>
Date: Wed, 07 Apr 2010 18:52:29 +0900
From: Tejun Heo <tj@...nel.org>
To: Jens Axboe <jens.axboe@...cle.com>,
lkml <linux-kernel@...r.kernel.org>,
Kay Sievers <kay.sievers@...y.org>,
Matthias-Christian Ott <ott@...ix.org>
Subject: [PATCH 1/2] block: factor out bd_may_claim()
Factor out bd_may_claim() from bd_claim(), add comments and apply a
couple of cosmetic edits. This is to prepare for further updates to
claim path.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
Jens, these two patches fix a subtle problem in block device open path
where O_EXCL open attempts can interfere with an already exclusively
open device.
These definitely are not for this merge window and need to get good
amount testing in linux-next.
Thanks.
fs/block_dev.c | 65 +++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 47 insertions(+), 18 deletions(-)
Index: work/fs/block_dev.c
===================================================================
--- work.orig/fs/block_dev.c
+++ work/fs/block_dev.c
@@ -660,41 +660,70 @@ void bd_forget(struct inode *inode)
iput(bdev->bd_inode);
}
-int bd_claim(struct block_device *bdev, void *holder)
+/**
+ * bd_may_claim - test whether a block device can be claimed
+ * @bdev: block device of interest
+ * @whole: whole block device containing @bdev, may equal @bdev
+ * @holder: holder trying to claim @bdev
+ *
+ * Test whther @bdev can be claimed by @holder.
+ *
+ * CONTEXT:
+ * spin_lock(&bdev_lock).
+ *
+ * RETURNS:
+ * %true if @bdev can be claimed, %false otherwise.
+ */
+static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
+ void *holder)
{
- int res;
- spin_lock(&bdev_lock);
-
- /* first decide result */
if (bdev->bd_holder == holder)
- res = 0; /* already a holder */
+ return true; /* already a holder */
else if (bdev->bd_holder != NULL)
- res = -EBUSY; /* held by someone else */
+ return false; /* held by someone else */
else if (bdev->bd_contains == bdev)
- res = 0; /* is a whole device which isn't held */
+ return true; /* is a whole device which isn't held */
- else if (bdev->bd_contains->bd_holder == bd_claim)
- res = 0; /* is a partition of a device that is being partitioned */
- else if (bdev->bd_contains->bd_holder != NULL)
- res = -EBUSY; /* is a partition of a held device */
+ else if (whole->bd_holder == bd_claim)
+ return true; /* is a partition of a device that is being partitioned */
+ else if (whole->bd_holder != NULL)
+ return false; /* is a partition of a held device */
else
- res = 0; /* is a partition of an un-held device */
+ return true; /* is a partition of an un-held device */
+}
- /* now impose change */
- if (res==0) {
+/**
+ * bd_claim - claim a block device
+ * @bdev: block device to claim
+ * @holder: holder trying to claim @bdev
+ *
+ * Try to claim @bdev.
+ *
+ * RETURNS:
+ * 0 if successful, -EBUSY if @bdev is already claimed.
+ */
+int bd_claim(struct block_device *bdev, void *holder)
+{
+ struct block_device *whole = bdev->bd_contains;
+ int res = -EBUSY;
+
+ spin_lock(&bdev_lock);
+
+ if (bd_may_claim(bdev, whole, holder)) {
/* note that for a whole device bd_holders
* will be incremented twice, and bd_holder will
* be set to bd_claim before being set to holder
*/
- bdev->bd_contains->bd_holders ++;
- bdev->bd_contains->bd_holder = bd_claim;
+ whole->bd_holders++;
+ whole->bd_holder = bd_claim;
bdev->bd_holders++;
bdev->bd_holder = holder;
+ res = 0;
}
+
spin_unlock(&bdev_lock);
return res;
}
-
EXPORT_SYMBOL(bd_claim);
void bd_release(struct block_device *bdev)
--
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