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authorChristian Brauner <brauner@kernel.org>2024-02-08 20:47:35 +0300
committerChristian Brauner <brauner@kernel.org>2024-02-25 14:05:21 +0300
commitf3a608827d1f8de0dd12813e8d9c6803fe64e119 (patch)
tree7072a00135288537c56348d8abf4ada7cd5fac7d /block
parentbac0a9e56e1fd14b227ab57142eca6f7bc6e6115 (diff)
downloadlinux-f3a608827d1f8de0dd12813e8d9c6803fe64e119.tar.xz
bdev: open block device as files
Add two new helpers to allow opening block devices as files. This is not the final infrastructure. This still opens the block device before opening a struct a file. Until we have removed all references to struct bdev_handle we can't switch the order: * Introduce blk_to_file_flags() to translate from block specific to flags usable to pen a new file. * Introduce bdev_file_open_by_{dev,path}(). * Introduce temporary sb_bdev_handle() helper to retrieve a struct bdev_handle from a block device file and update places that directly reference struct bdev_handle to rely on it. * Don't count block device openes against the number of open files. A bdev_file_open_by_{dev,path}() file is never installed into any file descriptor table. One idea that came to mind was to use kernel_tmpfile_open() which would require us to pass a path and it would then call do_dentry_open() going through the regular fops->open::blkdev_open() path. But then we're back to the problem of routing block specific flags such as BLK_OPEN_RESTRICT_WRITES through the open path and would have to waste FMODE_* flags every time we add a new one. With this we can avoid using a flag bit and we have more leeway in how we open block devices from bdev_open_by_{dev,path}(). Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-1-adbd023e19cc@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'block')
-rw-r--r--block/bdev.c101
1 files changed, 97 insertions, 4 deletions
diff --git a/block/bdev.c b/block/bdev.c
index e9f1b12bd75c..e1149652c532 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -49,6 +49,13 @@ struct block_device *I_BDEV(struct inode *inode)
}
EXPORT_SYMBOL(I_BDEV);
+struct block_device *file_bdev(struct file *bdev_file)
+{
+ struct bdev_handle *handle = bdev_file->private_data;
+ return handle->bdev;
+}
+EXPORT_SYMBOL(file_bdev);
+
static void bdev_write_inode(struct block_device *bdev)
{
struct inode *inode = bdev->bd_inode;
@@ -368,12 +375,12 @@ static struct file_system_type bd_type = {
};
struct super_block *blockdev_superblock __ro_after_init;
+struct vfsmount *blockdev_mnt __ro_after_init;
EXPORT_SYMBOL_GPL(blockdev_superblock);
void __init bdev_cache_init(void)
{
int err;
- static struct vfsmount *bd_mnt __ro_after_init;
bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
@@ -382,10 +389,10 @@ void __init bdev_cache_init(void)
err = register_filesystem(&bd_type);
if (err)
panic("Cannot register bdev pseudo-fs");
- bd_mnt = kern_mount(&bd_type);
- if (IS_ERR(bd_mnt))
+ blockdev_mnt = kern_mount(&bd_type);
+ if (IS_ERR(blockdev_mnt))
panic("Cannot create bdev pseudo-fs");
- blockdev_superblock = bd_mnt->mnt_sb; /* For writeback */
+ blockdev_superblock = blockdev_mnt->mnt_sb; /* For writeback */
}
struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
@@ -911,6 +918,92 @@ free_handle:
}
EXPORT_SYMBOL(bdev_open_by_dev);
+/*
+ * If BLK_OPEN_WRITE_IOCTL is set then this is a historical quirk
+ * associated with the floppy driver where it has allowed ioctls if the
+ * file was opened for writing, but does not allow reads or writes.
+ * Make sure that this quirk is reflected in @f_flags.
+ *
+ * It can also happen if a block device is opened as O_RDWR | O_WRONLY.
+ */
+static unsigned blk_to_file_flags(blk_mode_t mode)
+{
+ unsigned int flags = 0;
+
+ if ((mode & (BLK_OPEN_READ | BLK_OPEN_WRITE)) ==
+ (BLK_OPEN_READ | BLK_OPEN_WRITE))
+ flags |= O_RDWR;
+ else if (mode & BLK_OPEN_WRITE_IOCTL)
+ flags |= O_RDWR | O_WRONLY;
+ else if (mode & BLK_OPEN_WRITE)
+ flags |= O_WRONLY;
+ else if (mode & BLK_OPEN_READ)
+ flags |= O_RDONLY; /* homeopathic, because O_RDONLY is 0 */
+ else
+ WARN_ON_ONCE(true);
+
+ if (mode & BLK_OPEN_NDELAY)
+ flags |= O_NDELAY;
+
+ return flags;
+}
+
+struct file *bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
+ const struct blk_holder_ops *hops)
+{
+ struct file *bdev_file;
+ struct bdev_handle *handle;
+ unsigned int flags;
+
+ handle = bdev_open_by_dev(dev, mode, holder, hops);
+ if (IS_ERR(handle))
+ return ERR_CAST(handle);
+
+ flags = blk_to_file_flags(mode);
+ bdev_file = alloc_file_pseudo_noaccount(handle->bdev->bd_inode,
+ blockdev_mnt, "", flags | O_LARGEFILE, &def_blk_fops);
+ if (IS_ERR(bdev_file)) {
+ bdev_release(handle);
+ return bdev_file;
+ }
+ ihold(handle->bdev->bd_inode);
+
+ bdev_file->f_mode |= FMODE_BUF_RASYNC | FMODE_CAN_ODIRECT;
+ if (bdev_nowait(handle->bdev))
+ bdev_file->f_mode |= FMODE_NOWAIT;
+
+ bdev_file->f_mapping = handle->bdev->bd_inode->i_mapping;
+ bdev_file->f_wb_err = filemap_sample_wb_err(bdev_file->f_mapping);
+ bdev_file->private_data = handle;
+ return bdev_file;
+}
+EXPORT_SYMBOL(bdev_file_open_by_dev);
+
+struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
+ void *holder,
+ const struct blk_holder_ops *hops)
+{
+ struct file *bdev_file;
+ dev_t dev;
+ int error;
+
+ error = lookup_bdev(path, &dev);
+ if (error)
+ return ERR_PTR(error);
+
+ bdev_file = bdev_file_open_by_dev(dev, mode, holder, hops);
+ if (!IS_ERR(bdev_file) && (mode & BLK_OPEN_WRITE)) {
+ struct bdev_handle *handle = bdev_file->private_data;
+ if (bdev_read_only(handle->bdev)) {
+ fput(bdev_file);
+ bdev_file = ERR_PTR(-EACCES);
+ }
+ }
+
+ return bdev_file;
+}
+EXPORT_SYMBOL(bdev_file_open_by_path);
+
/**
* bdev_open_by_path - open a block device by name
* @path: path to the block device to open