Messages in this thread Patch in this message | | | Date | Sun, 5 Sep 2010 21:44:52 +1000 | From | Neil Brown <> | Subject | Re: [PATCH 0/6] overlay filesystem prototype |
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On Sun, 05 Sep 2010 19:37:10 +0900 "J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:
> > Miklos Szeredi: > > Changes since the last version: > ::: > > - get write ref on the upper layer on mount unless the overlay > > itself is mounted read-only > > I think it a good approach. > Although it may be harmless, write-ref will not be put when a user > executes, > - mount -o ro /overlay ^remount, I assume > - umount /overlay > It will be easy to fix by implementing s_op->remount().
Something like this?
(I have a few other patches queued up, but haven't tested anything properly yet).
NeilBrown
From 3a9e1d4f07c5d6fd18cc165537107dd31233ec1f Mon Sep 17 00:00:00 2001 From: NeilBrown <neilb@suse.de> Date: Sat, 4 Sep 2010 09:17:54 +1000 Subject: [PATCH] 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>
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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