From: Miklos Szeredi <mszeredi@xxxxxxx>
When the superblock is forcefully remounted read-only, as in case of
an emergency remount or filesystem errors, make sure that the mounts
belonging to the superblock are also marked read-only.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/internal.h | 1 +
fs/namespace.c | 16 ++++++++++++++++
fs/super.c | 16 ++++++++++++----
3 files changed, 29 insertions(+), 4 deletions(-)
Index: linux-2.6/fs/internal.h
===================================================================
--- linux-2.6.orig/fs/internal.h 2010-10-04 13:02:24.000000000 +0200
+++ linux-2.6/fs/internal.h 2010-10-04 15:09:49.000000000 +0200
@@ -72,6 +72,7 @@ extern struct vfsmount *copy_tree(struct
extern int sb_prepare_remount_readonly(struct super_block *);
extern void sb_cancel_remount_readonly(struct super_block *);
extern void sb_finish_remount_readonly(struct super_block *);
+extern void mark_mounts_readonly(struct super_block *);
extern void __init mnt_init(void);
Index: linux-2.6/fs/namespace.c
===================================================================
--- linux-2.6.orig/fs/namespace.c 2010-10-04 13:02:24.000000000 +0200
+++ linux-2.6/fs/namespace.c 2010-10-04 15:09:49.000000000 +0200
@@ -418,7 +418,13 @@ static int mnt_make_writable(struct vfsm
void sb_force_remount_readonly(struct super_block *sb)
{
+ struct vfsmount *mnt;
+
+ br_write_lock(vfsmount_lock);
+ list_for_each_entry(mnt, &sb->s_mounts, mnt_instance)
+ mnt->mnt_flags |= MNT_READONLY;
sb->s_flags |= MS_RDONLY;
+ br_write_unlock(vfsmount_lock);
}
EXPORT_SYMBOL(sb_force_remount_readonly);
@@ -477,6 +483,16 @@ void sb_finish_remount_readonly(struct s
wake_up_all(&sb->s_wait_remount_readonly);
}
+void mark_mounts_readonly(struct super_block *sb)
+{
+ struct vfsmount *mnt;
+
+ br_write_lock(vfsmount_lock);
+ list_for_each_entry(mnt, &sb->s_mounts, mnt_instance)
+ mnt->mnt_flags |= MNT_READONLY;
+ br_write_unlock(vfsmount_lock);
+}
+
void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
{
mnt->mnt_sb = sb;
Index: linux-2.6/fs/super.c
===================================================================
--- linux-2.6.orig/fs/super.c 2010-10-04 13:02:24.000000000 +0200
+++ linux-2.6/fs/super.c 2010-10-04 15:09:49.000000000 +0200
@@ -555,6 +555,7 @@ int do_remount_sb(struct super_block *sb
{
int retval;
int remount_ro;
+ bool old_ro;
if (sb->s_frozen != SB_UNFROZEN)
return -EBUSY;
@@ -569,12 +570,14 @@ int do_remount_sb(struct super_block *sb
shrink_dcache_sb(sb);
sync_filesystem(sb);
- remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
+ old_ro = (sb->s_flags & MS_RDONLY) != 0;
+ remount_ro = (flags & MS_RDONLY) && !old_ro;
/* If we are remounting RDONLY and current sb is read/write,
make sure there are no rw files opened */
if (remount_ro) {
if (force) {
+ mark_mounts_readonly(sb);
mark_files_ro(sb);
} else {
retval = sb_prepare_remount_readonly(sb);
@@ -596,9 +599,14 @@ int do_remount_sb(struct super_block *sb
return retval;
}
}
- if (remount_ro && !force)
- sb_finish_remount_readonly(sb);
-
+ if (remount_ro) {
+ WARN_ON(!(flags & MS_RDONLY));
+ if (!force)
+ sb_finish_remount_readonly(sb);
+ } else if ((flags & MS_RDONLY) && !old_ro) {
+ /* filesystem remounted r/o without being asked to */
+ sb_force_remount_readonly(sb);
+ }
sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
/*
--
--
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