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Commit ba6379f7 authored by Jan Kara's avatar Jan Kara
Browse files

fs: Provide function to get superblock with exclusive s_umount 



Quota code will need a variant of get_super_thawed() that returns
superblock with s_umount held in exclusive mode to serialize quota on
and quota off operations. Provide this functionality.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 9c763584

fs/super.c

+60 −20
Original line number Diff line number Diff line
@@ -558,6 +558,13 @@ void drop_super(struct super_block *sb) 


EXPORT_SYMBOL(drop_super);



void drop_super_exclusive(struct super_block *sb)

{

	up_write(&sb->s_umount);

	put_super(sb);

}

EXPORT_SYMBOL(drop_super_exclusive);



/**

 *	iterate_supers - call function for all active superblocks

 *	@f: function to call
@@ -628,15 +635,7 @@ void iterate_supers_type(struct file_system_type *type, 


EXPORT_SYMBOL(iterate_supers_type);



/**

 *	get_super - get the 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 given. %NULL is returned if no match is found.

 */



struct super_block *get_super(struct block_device *bdev)

static struct super_block *__get_super(struct block_device *bdev, bool excl)

{

	struct super_block *sb;
@@ -651,11 +650,17 @@ struct super_block *get_super(struct block_device *bdev) 
		if (sb->s_bdev == bdev) {

			sb->s_count++;

			spin_unlock(&sb_lock);

			if (!excl)

				down_read(&sb->s_umount);

			else

				down_write(&sb->s_umount);

			/* still alive? */

			if (sb->s_root && (sb->s_flags & MS_BORN))

				return sb;

			if (!excl)

				up_read(&sb->s_umount);

			else

				up_write(&sb->s_umount);

			/* nope, got unmounted */

			spin_lock(&sb_lock);

			__put_super(sb);
@@ -666,31 +671,66 @@ struct super_block *get_super(struct block_device *bdev) 
	return NULL;

}



EXPORT_SYMBOL(get_super);



/**

 *	get_super_thawed - get thawed superblock of a device

 *	get_super - get the 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.

 *	mounted on the device given. %NULL is returned if no match is found.

 */

struct super_block *get_super_thawed(struct block_device *bdev)

struct super_block *get_super(struct block_device *bdev)

{

	return __get_super(bdev, false);

}

EXPORT_SYMBOL(get_super);



static struct super_block *__get_super_thawed(struct block_device *bdev,

					      bool excl)

{

	while (1) {

		struct super_block *s = get_super(bdev);

		struct super_block *s = __get_super(bdev, excl);

		if (!s || s->s_writers.frozen == SB_UNFROZEN)

			return s;

		if (!excl)

			up_read(&s->s_umount);

		else

			up_write(&s->s_umount);

		wait_event(s->s_writers.wait_unfrozen,

			   s->s_writers.frozen == SB_UNFROZEN);

		put_super(s);

	}

}



/**

 *	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)

{

	return __get_super_thawed(bdev, false);

}

EXPORT_SYMBOL(get_super_thawed);



/**

 *	get_super_exclusive_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) and s_umount semaphore is held

 *	in exclusive mode. %NULL is returned if no match is found.

 */

struct super_block *get_super_exclusive_thawed(struct block_device *bdev)

{

	return __get_super_thawed(bdev, true);

}

EXPORT_SYMBOL(get_super_exclusive_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

+2 −0
Original line number Diff line number Diff line
@@ -2949,8 +2949,10 @@ 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_super_exclusive_thawed(struct block_device *bdev);

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

extern void drop_super(struct super_block *sb);

extern void drop_super_exclusive(struct super_block *sb);

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

extern void iterate_supers_type(struct file_system_type *,

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