[PATCH 12/20] 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.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/block/loop.c   | 12 +++-----
 fs/block_dev.c         | 69 +++++++++++++++++++-----------------------
 include/linux/blkdev.h |  6 ++--
 3 files changed, 38 insertions(+), 49 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b42c728620c9e4..599e94a7e69259 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1071,7 +1071,6 @@ 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;
@@ -1090,8 +1089,7 @@ 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->bd_contains;
-               error = bd_prepare_to_claim(bdev, claimed_bdev, loop_configure);
+               error = bd_prepare_to_claim(bdev, loop_configure);
                if (error)
                        goto out_putf;
        }
@@ -1178,15 +1176,15 @@ 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 e94633dc6ad93b..dd52dbd266cde7 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->bd_contains;
-               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);
@@ -1047,7 +1043,6 @@ 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
@@ -1057,9 +1052,10 @@ 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->bd_contains;
+
 retry:
        spin_lock(&bdev_lock);
        /* if someone else claimed, fail */
@@ -1099,15 +1095,15 @@ 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->bd_contains;
+
        spin_lock(&bdev_lock);
        BUG_ON(!bd_may_claim(bdev, whole, holder));
        /*
@@ -1132,11 +1128,10 @@ 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->bd_contains, holder);
        spin_unlock(&bdev_lock);
 }
 EXPORT_SYMBOL(bd_abort_claiming);
@@ -1434,7 +1429,7 @@ static void put_disk_and_module(struct gendisk *disk)
 static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
                int for_part)
 {
-       struct block_device *whole = NULL, *claiming = NULL;
+       struct block_device *whole = NULL;
        struct gendisk *disk = bdev->bd_disk;
        int ret;
        bool first_open = false, unblock_events = true, need_restart;
@@ -1462,11 +1457,7 @@ static int __blkdev_get(struct block_device *bdev, 
fmode_t mode, void *holder,
 
        if (!for_part && (mode & FMODE_EXCL)) {
                WARN_ON_ONCE(!holder);
-               if (whole)
-                       claiming = whole;
-               else
-                       claiming = bdev;
-               ret = bd_prepare_to_claim(bdev, claiming, holder);
+               ret = bd_prepare_to_claim(bdev, holder);
                if (ret)
                        goto out_put_whole;
        }
@@ -1543,21 +1534,23 @@ static int __blkdev_get(struct block_device *bdev, 
fmode_t mode, void *holder,
                }
        }
        bdev->bd_openers++;
-       if (for_part)
+       if (for_part) {
                bdev->bd_part_count++;
-       if (claiming)
-               bd_finish_claiming(bdev, claiming, holder);
+       } else if (mode & FMODE_EXCL) {
+               bd_finish_claiming(bdev, holder);
 
-       /*
-        * Block event polling for write claims if requested.  Any write holder
-        * makes the write_holder state stick until all are released.  This is
-        * good enough and tracking individual writeable reference is too
-        * fragile given the way @mode is used in blkdev_get/put().
-        */
-       if (claiming && (mode & FMODE_WRITE) && !bdev->bd_write_holder &&
-           (disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
-               bdev->bd_write_holder = true;
-               unblock_events = false;
+               /*
+                * Block event polling for write claims if requested.  Any write
+                * holder makes the write_holder state stick until all are
+                * released.  This is good enough and tracking individual
+                * writeable reference is too fragile given the way @mode is
+                * used in blkdev_get/put().
+                */
+               if ((mode & FMODE_WRITE) && !bdev->bd_write_holder &&
+                   (disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
+                       bdev->bd_write_holder = true;
+                       unblock_events = false;
+               }
        }
        mutex_unlock(&bdev->bd_mutex);
 
@@ -1578,8 +1571,8 @@ static int __blkdev_get(struct block_device *bdev, 
fmode_t mode, void *holder,
                __blkdev_put(bdev->bd_contains, mode, 1);
        bdev->bd_contains = NULL;
  out_unlock_bdev:
-       if (claiming)
-               bd_abort_claiming(bdev, claiming, holder);
+       if (!for_part && (mode & FMODE_EXCL))
+               bd_abort_claiming(bdev, holder);
        mutex_unlock(&bdev->bd_mutex);
        disk_unblock_events(disk);
  out_put_whole:
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 044d9dd159d882..696b2f9c5529d8 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