[PATCH 67/78] block: simplify the block device claiming interface

Christoph Hellwig
2020-11-16T15:12:59Z

Stop passing the whole device as a separate argument given that it
can be trivially deducted.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
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 f36788d7699302..fd4df132a97590 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);
@@ -1055,7 +1051,6 @@ 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
@@ -1065,9 +1060,10 @@ 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 */
@@ -1107,15 +1103,15 @@ 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));
/*
@@ -1140,11 +1136,10 @@ 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);
@@ -1439,7 +1434,7 @@ static int bdev_get_gendisk(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;
@@ -1460,11 +1455,7 @@ 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;
}
@@ -1541,21 +1532,23 @@ 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);

@@ -1576,8 +1569,8 @@ 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);