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Subject[PATCH] Replace obscure constructs in fs/block_dev.c
Hi,

Andrew, I promised it [1], here goes. Patched against Linus' git-tree.

[1] http://lkml.org/lkml/2007/3/22/226

This patch replaces some obscure code-paths in fs/block_dev.c with more
readable versions.

Signed-off-by: Johannes Weiner <hannes-kernel@saeurebad.de>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index ea1480a..1ffbb6d 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -660,26 +660,16 @@ void bd_forget(struct inode *inode)

int bd_claim(struct block_device *bdev, void *holder)
{
- int res;
+ int res = 0;
spin_lock(&bdev_lock);

- /* first decide result */
- if (bdev->bd_holder == holder)
- res = 0; /* already a holder */
- else if (bdev->bd_holder != NULL)
- res = -EBUSY; /* held by someone else */
- else if (bdev->bd_contains == bdev)
- res = 0; /* 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
- res = 0; /* is a partition of an un-held device */
+ /* If already held by someone else or we have a
+ * partition of a held device, we do nothing. */

- /* now impose change */
- if (res==0) {
+ if (bdev->bd_holder || bdev->bd_contains->bd_holder)
+ res = -EBUSY;
+
+ if (!res) {
/* 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
@@ -874,7 +864,7 @@ static struct bd_holder *find_bd_holder(struct block_device *bdev,
*/
static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
{
- int ret;
+ int err;

if (!bo)
return -EINVAL;
@@ -882,15 +872,18 @@ static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
if (!bd_holder_grab_dirs(bdev, bo))
return -EBUSY;

- ret = add_symlink(bo->sdir, bo->sdev);
- if (ret == 0) {
- ret = add_symlink(bo->hdir, bo->hdev);
- if (ret)
- del_symlink(bo->sdir, bo->sdev);
+ err = add_symlink(bo->sdir, bo->sdev);
+ if (err)
+ return err;
+
+ err = add_symlink(bo->hdir, bo->hdev);
+ if (err) {
+ del_symlink(bo->sdir, bo->sdev);
+ return err;
}
- if (ret == 0)
- list_add_tail(&bo->list, &bdev->bd_holder_list);
- return ret;
+
+ list_add_tail(&bo->list, &bdev->bd_holder_list);
+ return 0;
}

/**
@@ -948,7 +941,7 @@ static struct bd_holder *del_bd_holder(struct block_device *bdev,
static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
struct kobject *kobj)
{
- int res;
+ int err;
struct bd_holder *bo, *found;

if (!kobj)
@@ -959,21 +952,25 @@ static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
return -ENOMEM;

mutex_lock(&bdev->bd_mutex);
- res = bd_claim(bdev, holder);
- if (res == 0) {
- found = find_bd_holder(bdev, bo);
- if (found == NULL) {
- res = add_bd_holder(bdev, bo);
- if (res)
- bd_release(bdev);
- }
- }

- if (res || found)
+ err = bd_claim(bdev, holder);
+ if (err)
+ goto out;
+
+ found = find_bd_holder(bdev, bo);
+ if (found)
+ goto out;
+
+ err = add_bd_holder(bdev, bo);
+ if (err)
+ bd_release(bdev);
+
+out:
+ if (err || found)
free_bd_holder(bo);
- mutex_unlock(&bdev->bd_mutex);

- return res;
+ mutex_unlock(&bdev->bd_mutex);
+ return err;
}

/**
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