The patch titled
r/o bind mounts: honor r/w changes at do_remount() time
has been added to the -mm tree. Its filename is
ro-bind-mounts-honor-r-w-changes-at-do_remount-time.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: r/o bind mounts: honor r/w changes at do_remount() time
From: Dave Hansen <haveblue@xxxxxxxxxx>
Originally from: Herbert Poetzl <herbert@xxxxxxxxxxxx>
This is the core of the read-only bind mount patch set.
Note that this does _not_ add a "ro" option directly to the bind mount
operation. If you require such a mount, you must first do the bind, then
follow it up with a 'mount -o remount,ro' operation.
Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx>
Cc: Serge Hallyn <serue@xxxxxxxxxx>
Cc: Herbert Poetzl <herbert@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/namespace.c | 27 +++++++++++++++++++++++++--
fs/open.c | 2 +-
include/linux/mount.h | 19 +++++++++++++++++++
3 files changed, 45 insertions(+), 3 deletions(-)
diff -puN fs/namespace.c~ro-bind-mounts-honor-r-w-changes-at-do_remount-time fs/namespace.c
--- a/fs/namespace.c~ro-bind-mounts-honor-r-w-changes-at-do_remount-time
+++ a/fs/namespace.c
@@ -387,7 +387,10 @@ static int show_vfsmnt(struct seq_file *
seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
seq_putc(m, ' ');
mangle(m, mnt->mnt_sb->s_type->name);
- seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
+ if ((mnt->mnt_sb->s_flags & MS_RDONLY) || __mnt_is_readonly(mnt))
+ seq_puts(m, " ro");
+ else
+ seq_puts(m, " rw");
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_sb->s_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
@@ -956,6 +959,23 @@ out:
return err;
}
+static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
+{
+ int error = 0;
+ int readonly_request = 0;
+
+ if (ms_flags & MS_RDONLY)
+ readonly_request = 1;
+ if (readonly_request == __mnt_is_readonly(mnt))
+ return 0;
+
+ if (readonly_request)
+ error = mnt_make_readonly(mnt);
+ else
+ __mnt_make_writable(mnt);
+ return error;
+}
+
/*
* change filesystem flags. dir should be a physical root of filesystem.
* If you've mounted a non-root directory somewhere and want to do remount
@@ -977,7 +997,10 @@ static int do_remount(struct nameidata *
return -EINVAL;
down_write(&sb->s_umount);
- err = do_remount_sb(sb, flags, data, 0);
+ if (flags & MS_BIND)
+ err = change_mount_flags(nd->mnt, flags);
+ else
+ err = do_remount_sb(sb, flags, data, 0);
if (!err)
nd->mnt->mnt_flags = mnt_flags;
up_write(&sb->s_umount);
diff -puN fs/open.c~ro-bind-mounts-honor-r-w-changes-at-do_remount-time fs/open.c
--- a/fs/open.c~ro-bind-mounts-honor-r-w-changes-at-do_remount-time
+++ a/fs/open.c
@@ -546,7 +546,7 @@ asmlinkage long sys_faccessat(int dfd, c
special_file(nd.dentry->d_inode->i_mode))
goto out_path_release;
- if(IS_RDONLY(nd.dentry->d_inode))
+ if(mnt_is_readonly(nd.mnt) || IS_RDONLY(nd.dentry->d_inode))
res = -EROFS;
out_path_release:
diff -puN include/linux/mount.h~ro-bind-mounts-honor-r-w-changes-at-do_remount-time include/linux/mount.h
--- a/include/linux/mount.h~ro-bind-mounts-honor-r-w-changes-at-do_remount-time
+++ a/include/linux/mount.h
@@ -98,6 +98,25 @@ static inline int __mnt_is_readonly(stru
return (atomic_read(&mnt->mnt_writers) == 0);
}
+/*
+ * This needs to get a consistent look at mnt_writers.
+ * Without the lock, it can race against mnt_make_readonly()
+ * and mistake a temporarily decremented mnt_writers
+ * for a real read-only mount.
+ *
+ * Note: this is never suitable if you need to perform any
+ * write *operations* on the mount, only as a snapshot.
+ */
+static inline int mnt_is_readonly(struct vfsmount *mnt)
+{
+ int ret;
+
+ down_read(&mnt->mnt_sb->s_umount);
+ ret = __mnt_is_readonly(mnt);
+ up_read(&mnt->mnt_sb->s_umount);
+ return ret;
+}
+
static inline int mnt_want_write(struct vfsmount *mnt)
{
int ret = 0;
_
Patches currently in -mm which might be from haveblue@xxxxxxxxxx are
origin.patch
catch-notification-of-memory-add-event-of-acpi-via-container-driver-register-start-func-for-memory-device.patch
catch-notification-of-memory-add-event-of-acpi-via-container-driveravoid-redundant-call-add_memory.patch
pgdat-allocation-for-new-node-add-specify-node-id.patch
pgdat-allocation-for-new-node-add-get-node-id-by-acpi.patch
pgdat-allocation-for-new-node-add-generic-alloc-node_data.patch
pgdat-allocation-for-new-node-add-refresh-node_data.patch
pgdat-allocation-for-new-node-add-export-kswapd-start-func.patch
pgdat-allocation-for-new-node-add-call-pgdat-allocation.patch
node-hotplug-register-cpu-remove-node-struct.patch
acpi-dock-driver.patch
ro-bind-mounts-prepare-for-write-access-checks-collapse-if.patch
ro-bind-mounts-r-o-bind-mount-prepwork-move-open_nameis-vfs_create.patch
ro-bind-mounts-add-vfsmount-writer-count.patch
ro-bind-mounts-elevate-mnt-writers-for-callers-of-vfs_mkdir.patch
ro-bind-mounts-elevate-write-count-during-entire-ncp_ioctl.patch
ro-bind-mounts-sys_symlinkat-elevate-write-count-around-vfs_symlink.patch
ro-bind-mounts-elevate-mount-count-for-extended-attributes.patch
ro-bind-mounts-sys_linkat-elevate-write-count-around-vfs_link.patch
ro-bind-mounts-mount_is_safe-add-comment.patch
ro-bind-mounts-unix_find_other-elevate-write-count-for-touch_atime.patch
ro-bind-mounts-elevate-write-count-over-calls-to-vfs_rename.patch
ro-bind-mounts-tricky-elevate-write-count-files-are-opened.patch
ro-bind-mounts-elevate-writer-count-for-do_sys_truncate.patch
ro-bind-mounts-elevate-write-count-for-do_utimes.patch
ro-bind-mounts-elevate-write-count-for-do_sys_utime-and-touch_atime.patch
ro-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create.patch
ro-bind-mounts-elevate-mnt-writers-for-vfs_unlink-callers.patch
ro-bind-mounts-do_rmdir-elevate-write-count.patch
ro-bind-mounts-elevate-writer-count-for-custom-struct-file.patch
ro-bind-mounts-honor-r-w-changes-at-do_remount-time.patch
page-owner-tracking-leak-detector.patch
x86-e820-debugging.patch
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