[PATCH 02/29] block: Use bdev_open_by_dev() in blkdev_open()

Jan Kara
2023-09-27T09:34:51Z

Convert blkdev_open() to use bdev_open_by_dev(). To be able to propagate
handle from blkdev_open() to blkdev_release() we need to stop using
existence of file->private_data to determine exclusive block device
opens. Use bdev_handle->mode for this purpose since file->f_flags
isn't usable for this (O_EXCL is cleared from the flags during open).

Acked-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
block/bdev.c | 3 +++
block/fops.c | 44 +++++++++++++++++++++++++++---------------
include/linux/blkdev.h | 1 +
3 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index bdc7d739882b..4628dcb1da8a 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -844,6 +844,9 @@ struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
}
handle->bdev = bdev;
handle->holder = holder;
+ if (holder)
+ mode |= BLK_OPEN_EXCL;
+ handle->mode = mode;
return handle;
}
EXPORT_SYMBOL(bdev_open_by_dev);
diff --git a/block/fops.c b/block/fops.c
index acff3d5d22d4..91e9cf2fca24 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -542,15 +542,31 @@ static int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
return error;
}

+/**
+ * file_to_blk_mode - get block open flags from file flags
+ * @file: file whose open flags should be converted
+ *
+ * Look at file open flags and generate corresponding block open flags from
+ * them. The function works both for file just being open (e.g. during ->open
+ * callback) and for file that is already open. This is actually non-trivial
+ * (see comment in the function).
+ */
blk_mode_t file_to_blk_mode(struct file *file)
{
blk_mode_t mode = 0;
+ struct bdev_handle *handle = file->private_data;

if (file->f_mode & FMODE_READ)
mode |= BLK_OPEN_READ;
if (file->f_mode & FMODE_WRITE)
mode |= BLK_OPEN_WRITE;
- if (file->private_data)
+ /*
+ * do_dentry_open() clears O_EXCL from f_flags, use handle->mode to
+ * determine whether the open was exclusive for already open files.
+ */
+ if (handle)
+ mode |= handle->mode & BLK_OPEN_EXCL;
+ else if (file->f_flags & O_EXCL)
mode |= BLK_OPEN_EXCL;
if (file->f_flags & O_NDELAY)
mode |= BLK_OPEN_NDELAY;
@@ -568,7 +584,8 @@ blk_mode_t file_to_blk_mode(struct file *file)

static int blkdev_open(struct inode *inode, struct file *filp)
{
- struct block_device *bdev;
+ struct bdev_handle *handle;
+ blk_mode_t mode;

/*
* Preserve backwards compatibility and allow large file access
@@ -579,29 +596,24 @@ static int blkdev_open(struct inode *inode, struct file *filp)
filp->f_flags |= O_LARGEFILE;
filp->f_mode |= FMODE_BUF_RASYNC | FMODE_CAN_ODIRECT;

- /*
- * Use the file private data to store the holder for exclusive openes.
- * file_to_blk_mode relies on it being present to set BLK_OPEN_EXCL.
- */
- if (filp->f_flags & O_EXCL)
- filp->private_data = filp;
-
- bdev = blkdev_get_by_dev(inode->i_rdev, file_to_blk_mode(filp),
- filp->private_data, NULL);
- if (IS_ERR(bdev))
- return PTR_ERR(bdev);
+ mode = file_to_blk_mode(filp);
+ handle = bdev_open_by_dev(inode->i_rdev, mode,
+ mode & BLK_OPEN_EXCL ? filp : NULL, NULL);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);

- if (bdev_nowait(bdev))
+ if (bdev_nowait(handle->bdev))
filp->f_mode |= FMODE_NOWAIT;

- filp->f_mapping = bdev->bd_inode->i_mapping;
+ filp->f_mapping = handle->bdev->bd_inode->i_mapping;
filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
+ filp->private_data = handle;
return 0;
}

static int blkdev_release(struct inode *inode, struct file *filp)
{
- blkdev_put(I_BDEV(filp->f_mapping->host), filp->private_data);
+ bdev_release(filp->private_data);
return 0;
}

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 03d3adc3ff34..51fa7ffdee83 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1482,6 +1482,7 @@ extern const struct blk_holder_ops fs_holder_ops;
struct bdev_handle {
struct block_device *bdev;
void *holder;
+ blk_mode_t mode;
};

struct block_device *blkdev_get_by_dev(dev_t dev, blk_mode_t mode, void *holder,
--
2.35.3