Messages in this thread Patch in this message | | | Subject | [RFC][PATCH 1/2] pin kern mounts as writable | From | Dave Hansen <> | Date | Mon, 03 Aug 2009 14:59:40 -0700 |
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If we are going to continue to use mnt_clone_write() inside of init_file(), then we're going to need some kind of extra handling.
What I want to do in the next patch is add a debugging check in mnt_clone_write() to double-check that there *is* a real writer on the mount before mnt_clone_write() succeeds. To do that, we either need to check for MS_KERNMOUNT around that debug check, or we need to make sure that these kern mounts *have* a write already.
I'm choosing to make sure they always have a write.
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linux-2.6.git-dave/fs/super.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff -puN fs/super.c~pin-mnt-writable fs/super.c --- linux-2.6.git/fs/super.c~pin-mnt-writable 2009-08-03 14:47:29.000000000 -0700 +++ linux-2.6.git-dave/fs/super.c 2009-08-03 14:49:49.000000000 -0700 @@ -948,7 +948,19 @@ EXPORT_SYMBOL_GPL(do_kern_mount); struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) { - return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); + int err = 0; + struct vfsmount *mnt; + mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); + if (IS_ERR(mnt)) + return mnt; + /* + * We will never allow this mount to be r/o. Doing + * this makes it explicit and allows mnt_clone_write() + * to be used unconditionally on this mount. + */ + err = mnt_want_write(mnt); + WARN_ON(err); + return mnt; } EXPORT_SYMBOL_GPL(kern_mount_data); diff -puN include/linux/mount.h~pin-mnt-writable include/linux/mount.h _
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