This allows a vfsmount to keep track of how many instances
of files open for write there are at a given time. This
will be useful if it is ever desired to change a mount
from r/w to r/o at runtime.
A mount can also potentially refuse to allow writers; this
is why mnt_want_write() has a return value. However, that
functionality will be added later in the series. For now,
always allow new writers.
Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx>
---
lxc-dave/fs/namespace.c | 1 +
lxc-dave/include/linux/mount.h | 14 ++++++++++++++
2 files changed, 15 insertions(+)
diff -puN fs/namespace.c~convert-permission-to-file-and-vfs fs/namespace.c
--- lxc/fs/namespace.c~convert-permission-to-file-and-vfs 2006-06-07 16:53:11.000000000 -0700
+++ lxc-dave/fs/namespace.c 2006-06-07 16:53:11.000000000 -0700
@@ -66,6 +66,7 @@ struct vfsmount *alloc_vfsmnt(const char
if (mnt) {
memset(mnt, 0, sizeof(struct vfsmount));
atomic_set(&mnt->mnt_count, 1);
+ /* atomic_set(&mnt->writer_count, 0); */
INIT_LIST_HEAD(&mnt->mnt_hash);
INIT_LIST_HEAD(&mnt->mnt_child);
INIT_LIST_HEAD(&mnt->mnt_mounts);
diff -puN include/linux/mount.h~convert-permission-to-file-and-vfs include/linux/mount.h
--- lxc/include/linux/mount.h~convert-permission-to-file-and-vfs 2006-06-07 16:53:11.000000000 -0700
+++ lxc-dave/include/linux/mount.h 2006-06-07 16:53:11.000000000 -0700
@@ -12,6 +12,8 @@
#define _LINUX_MOUNT_H
#ifdef __KERNEL__
+#include <linux/err.h>
+#include <linux/fs.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/spinlock.h>
@@ -38,6 +40,7 @@ struct vfsmount {
struct list_head mnt_mounts; /* list of children, anchored here */
struct list_head mnt_child; /* and going through their mnt_child */
atomic_t mnt_count;
+ atomic_t mnt_writers;
int mnt_flags;
int mnt_expiry_mark; /* true if marked for expiry */
char *mnt_devname; /* Name of device e.g. /dev/dsk/hda1 */
@@ -58,6 +61,17 @@ static inline struct vfsmount *mntget(st
return mnt;
}
+static inline int mnt_want_write(struct vfsmount *mnt)
+{
+ atomic_inc(&mnt->mnt_writers);
+ return 0;
+}
+
+static inline void mnt_drop_write(struct vfsmount *mnt)
+{
+ atomic_dec(&mnt->mnt_writers);
+}
+
extern void mntput_no_expire(struct vfsmount *mnt);
extern void mnt_pin(struct vfsmount *mnt);
extern void mnt_unpin(struct vfsmount *mnt);
diff -L convert-permission-to-file-and-vfs -puN /dev/null /dev/null
diff -L convert-permission-to-file-and-vfs.patch -puN /dev/null /dev/null
_
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