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Commit 46b15caa authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB 



FS_CGROUP_WRITEBACK indicates whether a file_system_type supports
cgroup writeback; however, different super_blocks of the same
file_system_type may or may not support cgroup writeback depending on
filesystem options.  This patch replaces FS_CGROUP_WRITEBACK with a
per-super_block flag.

super_block->s_flags carries some internal flags in the high bits but
it's exposd to userland through uapi header and running out of space
anyway.  This patch adds a new field super_block->s_iflags to carry
kernel-internal flags.  It is currently only used by the new
SB_I_CGROUPWB flag whose concatenated and abbreviated name is for
consistency with other super_block flags.

ext2_fill_super() is updated to set SB_I_CGROUPWB.

v2: Added super_block->s_iflags instead of stealing another high bit
    from sb->s_flags as suggested by Christoph and Jan.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent dd73e4b7

fs/ext2/super.c

+2 −1
Original line number Diff line number Diff line
@@ -882,6 +882,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent) 
	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |

		((EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ?

		 MS_POSIXACL : 0);

	sb->s_iflags |= SB_I_CGROUPWB;



	if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV &&

	    (EXT2_HAS_COMPAT_FEATURE(sb, ~0U) ||
@@ -1543,7 +1544,7 @@ static struct file_system_type ext2_fs_type = { 
	.name		= "ext2",

	.mount		= ext2_mount,

	.kill_sb	= kill_block_super,

	.fs_flags	= FS_REQUIRES_DEV | FS_CGROUP_WRITEBACK,

	.fs_flags	= FS_REQUIRES_DEV,

};

MODULE_ALIAS_FS("ext2");

include/linux/backing-dev.h

+1 −1
Original line number Diff line number Diff line
@@ -260,7 +260,7 @@ static inline bool inode_cgwb_enabled(struct inode *inode) 


	return bdi_cap_account_dirty(bdi) &&

		(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&

		(inode->i_sb->s_type->fs_flags & FS_CGROUP_WRITEBACK);

		(inode->i_sb->s_iflags & SB_I_CGROUPWB);

}



/**

include/linux/fs.h

+3 −1
Original line number Diff line number Diff line
@@ -1241,6 +1241,8 @@ struct mm_struct; 
#define UMOUNT_NOFOLLOW	0x00000008	/* Don't follow symlink on umount */

#define UMOUNT_UNUSED	0x80000000	/* Flag guaranteed to be unused */



/* sb->s_iflags */

#define SB_I_CGROUPWB	0x00000001	/* cgroup-aware writeback enabled */



/* Possible states of 'frozen' field */

enum {
@@ -1279,6 +1281,7 @@ struct super_block { 
	const struct quotactl_ops	*s_qcop;

	const struct export_operations *s_export_op;

	unsigned long		s_flags;

	unsigned long		s_iflags;	/* internal SB_I_* flags */

	unsigned long		s_magic;

	struct dentry		*s_root;

	struct rw_semaphore	s_umount;
@@ -1912,7 +1915,6 @@ struct file_system_type { 
#define FS_HAS_SUBTYPE		4

#define FS_USERNS_MOUNT		8	/* Can be mounted by userns root */

#define FS_USERNS_DEV_MOUNT	16 /* A userns mount does not imply MNT_NODEV */

#define FS_CGROUP_WRITEBACK	32	/* Supports cgroup-aware writeback */

#define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move() during rename() internally. */

	struct dentry *(*mount) (struct file_system_type *, int,

		       const char *, void *);