[PATCH 27/45] block: simplify the block device claiming interface

[Christoph Hellwig <hch@xxxxxx>]

Stop passing the whole device as a separate argument given that it
can be trivially deducted and cleanup the !holder debug check.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
 drivers/block/loop.c   | 12 +++++-----
 fs/block_dev.c         | 51 +++++++++++++++---------------------------
 include/linux/blkdev.h |  6 ++---
 3 files changed, 25 insertions(+), 44 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c0df88b3300c41..d643c67be6acea 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1069,7 +1069,6 @@ static int loop_configure(struct loop_device *lo, fmode_t 
mode,
        struct file     *file;
        struct inode    *inode;
        struct address_space *mapping;
-       struct block_device *claimed_bdev = NULL;
        int             error;
        loff_t          size;
        bool            partscan;
@@ -1088,8 +1087,7 @@ static int loop_configure(struct loop_device *lo, fmode_t 
mode,
         * here to avoid changing device under exclusive owner.
         */
        if (!(mode & FMODE_EXCL)) {
-               claimed_bdev = bdev_whole(bdev);
-               error = bd_prepare_to_claim(bdev, claimed_bdev, loop_configure);
+               error = bd_prepare_to_claim(bdev, loop_configure);
                if (error)
                        goto out_putf;
        }
@@ -1176,15 +1174,15 @@ static int loop_configure(struct loop_device *lo, 
fmode_t mode,
        mutex_unlock(&loop_ctl_mutex);
        if (partscan)
                loop_reread_partitions(lo, bdev);
-       if (claimed_bdev)
-               bd_abort_claiming(bdev, claimed_bdev, loop_configure);
+       if (!(mode & FMODE_EXCL))
+               bd_abort_claiming(bdev, loop_configure);
        return 0;
 
 out_unlock:
        mutex_unlock(&loop_ctl_mutex);
 out_bdev:
-       if (claimed_bdev)
-               bd_abort_claiming(bdev, claimed_bdev, loop_configure);
+       if (!(mode & FMODE_EXCL))
+               bd_abort_claiming(bdev, loop_configure);
 out_putf:
        fput(file);
 out:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index e8d7de5fae00a9..43a0fda982c879 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -110,24 +110,20 @@ EXPORT_SYMBOL(invalidate_bdev);
 int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
                        loff_t lstart, loff_t lend)
 {
-       struct block_device *claimed_bdev = NULL;
-       int err;
-
        /*
         * If we don't hold exclusive handle for the device, upgrade to it
         * while we discard the buffer cache to avoid discarding buffers
         * under live filesystem.
         */
        if (!(mode & FMODE_EXCL)) {
-               claimed_bdev = bdev_whole(bdev);
-               err = bd_prepare_to_claim(bdev, claimed_bdev,
-                                         truncate_bdev_range);
+               int err = bd_prepare_to_claim(bdev, truncate_bdev_range);
                if (err)
                        return err;
        }
+
        truncate_inode_pages_range(bdev->bd_inode->i_mapping, lstart, lend);
-       if (claimed_bdev)
-               bd_abort_claiming(bdev, claimed_bdev, truncate_bdev_range);
+       if (!(mode & FMODE_EXCL))
+               bd_abort_claiming(bdev, truncate_bdev_range);
        return 0;
 }
 EXPORT_SYMBOL(truncate_bdev_range);
@@ -973,7 +969,6 @@ static bool bd_may_claim(struct block_device *bdev, struct 
block_device *whole,
 /**
  * bd_prepare_to_claim - claim a block device
  * @bdev: block device of interest
- * @whole: the whole device containing @bdev, may equal @bdev
  * @holder: holder trying to claim @bdev
  *
  * Claim @bdev.  This function fails if @bdev is already claimed by another
@@ -983,9 +978,12 @@ static bool bd_may_claim(struct block_device *bdev, struct 
block_device *whole,
  * RETURNS:
  * 0 if @bdev can be claimed, -EBUSY otherwise.
  */
-int bd_prepare_to_claim(struct block_device *bdev, struct block_device *whole,
-               void *holder)
+int bd_prepare_to_claim(struct block_device *bdev, void *holder)
 {
+       struct block_device *whole = bdev_whole(bdev);
+
+       if (WARN_ON_ONCE(!holder))
+               return -EINVAL;
 retry:
        spin_lock(&bdev_lock);
        /* if someone else claimed, fail */
@@ -1025,15 +1023,15 @@ static void bd_clear_claiming(struct block_device 
*whole, void *holder)
 /**
  * bd_finish_claiming - finish claiming of a block device
  * @bdev: block device of interest
- * @whole: whole block device
  * @holder: holder that has claimed @bdev
  *
  * Finish exclusive open of a block device. Mark the device as exlusively
  * open by the holder and wake up all waiters for exclusive open to finish.
  */
-static void bd_finish_claiming(struct block_device *bdev,
-               struct block_device *whole, void *holder)
+static void bd_finish_claiming(struct block_device *bdev, void *holder)
 {
+       struct block_device *whole = bdev_whole(bdev);
+
        spin_lock(&bdev_lock);
        BUG_ON(!bd_may_claim(bdev, whole, holder));
        /*
@@ -1058,11 +1056,10 @@ static void bd_finish_claiming(struct block_device 
*bdev,
  * also used when exclusive open is not actually desired and we just needed
  * to block other exclusive openers for a while.
  */
-void bd_abort_claiming(struct block_device *bdev, struct block_device *whole,
-                      void *holder)
+void bd_abort_claiming(struct block_device *bdev, void *holder)
 {
        spin_lock(&bdev_lock);
-       bd_clear_claiming(whole, holder);
+       bd_clear_claiming(bdev_whole(bdev), holder);
        spin_unlock(&bdev_lock);
 }
 EXPORT_SYMBOL(bd_abort_claiming);
@@ -1473,7 +1470,6 @@ static struct block_device 
*get_bdev_disk_and_module(dev_t dev)
  */
 struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
 {
-       struct block_device *claiming;
        bool unblock_events = true;
        struct block_device *bdev;
        struct gendisk *disk;
@@ -1496,15 +1492,9 @@ struct block_device *blkdev_get_by_dev(dev_t dev, 
fmode_t mode, void *holder)
        disk = bdev->bd_disk;
  
        if (mode & FMODE_EXCL) {
-               WARN_ON_ONCE(!holder);
-       
-               ret = -ENOMEM;
-               claiming = bdget_disk(disk, 0);
-               if (!claiming)
-                       goto put_disk;
-               ret = bd_prepare_to_claim(bdev, claiming, holder);
+               ret = bd_prepare_to_claim(bdev, holder);
                if (ret)
-                       goto put_claiming;
+                       goto put_disk;
        }
 
        disk_block_events(disk);
@@ -1514,7 +1504,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t 
mode, void *holder)
        if (ret)
                goto abort_claiming;
        if (mode & FMODE_EXCL) {
-               bd_finish_claiming(bdev, claiming, holder);
+               bd_finish_claiming(bdev, holder);
 
                /*
                 * Block event polling for write claims if requested.  Any write
@@ -1533,18 +1523,13 @@ struct block_device *blkdev_get_by_dev(dev_t dev, 
fmode_t mode, void *holder)
 
        if (unblock_events)
                disk_unblock_events(disk);
-       if (mode & FMODE_EXCL)
-               bdput(claiming);
        return bdev;
 
 abort_claiming:
        if (mode & FMODE_EXCL)
-               bd_abort_claiming(bdev, claiming, holder);
+               bd_abort_claiming(bdev, holder);
        mutex_unlock(&bdev->bd_mutex);
        disk_unblock_events(disk);
-put_claiming:
-       if (mode & FMODE_EXCL)
-               bdput(claiming);
 put_disk:
        module_put(disk->fops->owner);
        put_disk(disk);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 48e5a8393cd793..db1b11d6d07568 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1988,10 +1988,8 @@ void blkdev_show(struct seq_file *seqf, off_t offset);
 struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
                void *holder);
 struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder);
-int bd_prepare_to_claim(struct block_device *bdev, struct block_device *whole,
-               void *holder);
-void bd_abort_claiming(struct block_device *bdev, struct block_device *whole,
-               void *holder);
+int bd_prepare_to_claim(struct block_device *bdev, void *holder);
+void bd_abort_claiming(struct block_device *bdev, void *holder);
 void blkdev_put(struct block_device *bdev, fmode_t mode);
 
 struct block_device *bdev_alloc(struct gendisk *disk, u8 partno);
-- 
2.29.2