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Date: Tue, 12 Feb 2008 21:45:15 -0800
From: Paul Menage <menage@...gle.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org
Subject: [PATCH] Add MS_BIND_FLAGS mount flag
From: Paul Menage <menage@...gle.com>
Add a new mount() flag, MS_BIND_FLAGS.
MS_BIND_FLAGS indicates that a bind mount should take its per-mount flags
from the arguments passed to mount() rather than from the source
mountpoint.
This flag allows you to create a bind mount with the desired per-mount
flags in a single operation, rather than having to do a bind mount
followed by a remount, which is fiddly and can block for non-trivial
periods of time (on sb->s_umount?).
For recursive bind mounts, only the root of the tree being bound
inherits the per-mount flags from the mount() arguments; sub-mounts
inherit their per-mount flags from the source tree as usual.
Signed-off-by: Paul Menage <menage@...gle.com>
---
fs/namespace.c | 36 +++++++++++++++++++++++++-----------
include/linux/fs.h | 2 ++
2 files changed, 27 insertions(+), 11 deletions(-)
Index: 2.6.24-mm1-bindflags/fs/namespace.c
===================================================================
--- 2.6.24-mm1-bindflags.orig/fs/namespace.c
+++ 2.6.24-mm1-bindflags/fs/namespace.c
@@ -512,13 +512,13 @@ static struct vfsmount *skip_mnt_tree(st
}
static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
- int flag)
+ int flag, int mnt_flags)
{
struct super_block *sb = old->mnt_sb;
struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
if (mnt) {
- mnt->mnt_flags = old->mnt_flags;
+ mnt->mnt_flags = mnt_flags;
atomic_inc(&sb->s_active);
mnt->mnt_sb = sb;
mnt->mnt_root = dget(root);
@@ -1095,8 +1095,9 @@ static int lives_below_in_same_fs(struct
}
}
-struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
- int flag)
+static struct vfsmount *
+__copy_tree(struct vfsmount *mnt, struct dentry *dentry,
+ int flag, int mnt_flags)
{
struct vfsmount *res, *p, *q, *r, *s;
struct nameidata nd;
@@ -1104,7 +1105,7 @@ struct vfsmount *copy_tree(struct vfsmou
if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
return NULL;
- res = q = clone_mnt(mnt, dentry, flag);
+ res = q = clone_mnt(mnt, dentry, flag, mnt_flags);
if (!q)
goto Enomem;
q->mnt_mountpoint = mnt->mnt_mountpoint;
@@ -1126,7 +1127,7 @@ struct vfsmount *copy_tree(struct vfsmou
p = s;
nd.path.mnt = q;
nd.path.dentry = p->mnt_mountpoint;
- q = clone_mnt(p, p->mnt_root, flag);
+ q = clone_mnt(p, p->mnt_root, flag, p->mnt_flags);
if (!q)
goto Enomem;
spin_lock(&vfsmount_lock);
@@ -1146,6 +1147,11 @@ Enomem:
}
return NULL;
}
+struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
+ int flag)
+{
+ return __copy_tree(mnt, dentry, flag, mnt->mnt_flags);
+}
struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry)
{
@@ -1320,7 +1326,8 @@ static int do_change_type(struct nameida
/*
* do loopback mount.
*/
-static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
+static int do_loopback(struct nameidata *nd, char *old_name, int flags,
+ int mnt_flags)
{
struct nameidata old_nd;
struct vfsmount *mnt = NULL;
@@ -1342,10 +1349,15 @@ static int do_loopback(struct nameidata
goto out;
err = -ENOMEM;
- if (recurse)
- mnt = copy_tree(old_nd.path.mnt, old_nd.path.dentry, 0);
+ /* Use the source mount flags unless the user passed MS_BIND_FLAGS */
+ if (!(flags & MS_BIND_FLAGS))
+ mnt_flags = old_nd.path.mnt->mnt_flags;
+ if (flags & MS_REC)
+ mnt = __copy_tree(old_nd.path.mnt, old_nd.path.dentry, 0,
+ mnt_flags);
else
- mnt = clone_mnt(old_nd.path.mnt, old_nd.path.dentry, 0);
+ mnt = clone_mnt(old_nd.path.mnt, old_nd.path.dentry, 0,
+ mnt_flags);
if (!mnt)
goto out;
@@ -1874,7 +1886,9 @@ long do_mount(char *dev_name, char *dir_
retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
data_page);
else if (flags & MS_BIND)
- retval = do_loopback(&nd, dev_name, flags & MS_REC);
+ retval = do_loopback(&nd, dev_name,
+ flags & (MS_REC | MS_BIND_FLAGS),
+ mnt_flags);
else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
retval = do_change_type(&nd, flags);
else if (flags & MS_MOVE)
Index: 2.6.24-mm1-bindflags/include/linux/fs.h
===================================================================
--- 2.6.24-mm1-bindflags.orig/include/linux/fs.h
+++ 2.6.24-mm1-bindflags/include/linux/fs.h
@@ -125,6 +125,8 @@ extern int dir_notify_enable;
#define MS_RELATIME (1<<21) /* Update atime relative to mtime/ctime. */
#define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */
#define MS_I_VERSION (1<<23) /* Update inode I_version field */
+#define MS_BIND_FLAGS (1<<24) /* For MS_BIND, take mnt_flags from
+ * args, not from source mountpoint */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)
--
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