Commit 6b6dc836 authored by Jan Kara's avatar Jan Kara Committed by Al Viro
Browse files

vfs: Provide function to get superblock and wait for it to thaw 



In quota code we need to find a superblock corresponding to a device and wait
for superblock to be unfrozen. However this waiting has to happen without
s_umount semaphore because that is required for superblock to thaw. So provide
a function in VFS for this to keep dances with s_umount where they belong.

[AV: implementation switched to saner variant]

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 074b8517

fs/super.c

+22 −0
Original line number Diff line number Diff line
@@ -633,6 +633,28 @@ rescan: 


EXPORT_SYMBOL(get_super);



/**

 *	get_super_thawed - get thawed superblock of a device

 *	@bdev: device to get the superblock for

 *

 *	Scans the superblock list and finds the superblock of the file system

 *	mounted on the device. The superblock is returned once it is thawed

 *	(or immediately if it was not frozen). %NULL is returned if no match

 *	is found.

 */

struct super_block *get_super_thawed(struct block_device *bdev)

{

	while (1) {

		struct super_block *s = get_super(bdev);

		if (!s || s->s_frozen == SB_UNFROZEN)

			return s;

		up_read(&s->s_umount);

		vfs_check_frozen(s, SB_FREEZE_WRITE);

		put_super(s);

	}

}

EXPORT_SYMBOL(get_super_thawed);



/**

 * get_active_super - get an active reference to the superblock of a device

 * @bdev: device to get the superblock for

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -2496,6 +2496,7 @@ extern void get_filesystem(struct file_system_type *fs); 
extern void put_filesystem(struct file_system_type *fs);

extern struct file_system_type *get_fs_type(const char *name);

extern struct super_block *get_super(struct block_device *);

extern struct super_block *get_super_thawed(struct block_device *);

extern struct super_block *get_active_super(struct block_device *bdev);

extern void drop_super(struct super_block *sb);

extern void iterate_supers(void (*)(struct super_block *, void *), void *);

CRA Git | Maintained and supported by SUSTech CRA and CCSE