Messages in this thread Patch in this message |  | | Date | Tue, 12 Feb 2008 21:45:15 -0800 | | From | Paul Menage <> | | Subject | [PATCH] Add MS_BIND_FLAGS mount flag |
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From: Paul Menage <menage@google.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@google.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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