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Subject[PATCH 02/10] ovl: minimal remount support.
As overlayfs reflects the 'readonly' mount status in write-access to
the upper filesystem, we must handle remount and either drop or take
write access when the ro status changes.

Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/overlayfs/overlayfs.c | 20 ++++++++++++++++++++
1 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/fs/overlayfs/overlayfs.c b/fs/overlayfs/overlayfs.c
index 0ddfeec..4e032e8 100644
--- a/fs/overlayfs/overlayfs.c
+++ b/fs/overlayfs/overlayfs.c
@@ -1685,8 +1685,28 @@ static void ovl_put_super(struct super_block *sb)
kfree(ufs);
}

+static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
+{
+ int flags = *flagsp;
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ /* When remounting rw or ro, we need to adjust the write access to the
+ * upper fs.
+ */
+ if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
+ /* No change to readonly status */
+ return 0;
+
+ if (flags & MS_RDONLY) {
+ mnt_drop_write(ufs->upper_mnt);
+ return 0;
+ } else
+ return mnt_want_write(ufs->upper_mnt);
+}
+
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
+ .remount_fs = ovl_remount_fs,
};

struct ovl_config {



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