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vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB

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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: Tejun 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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-06-16 18:48:31 -04:00 committed by Jens Axboe
parent dd73e4b7df
commit 46b15caa7c
3 changed files with 6 additions and 3 deletions
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3
fs/ext2/super.c
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@ -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");

2
include/linux/backing-dev.h
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@ -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);
}
/**

4
include/linux/fs.h
View File

@ -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 *);