[PATCH] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion

[PATCH] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion

[David Howells]

In do_mount() when the MS_* flags are being converted to MNT_* flags,
MS_RDONLY got accidentally convered to SB_RDONLY.

Undo this change.

Fixes: e462ec50cb5f ("VFS: Differentiate mount flags (MS_*) from internal superblock flags")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/namespace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index e398f32d7541..6f720ebca133 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2814,7 +2814,7 @@ long do_mount(const char *dev_name, const char __user *dir_name,
 		mnt_flags |= MNT_NODIRATIME;
 	if (flags & MS_STRICTATIME)
 		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
-	if (flags & SB_RDONLY)
+	if (flags & MS_RDONLY)
 		mnt_flags |= MNT_READONLY;
 
 	/* The default atime for remount is preservation */

Re: [PATCH] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion

[Linus Torvalds]

On Fri, Apr 20, 2018 at 5:35 AM, David Howells <dhowells@redhat.com> wrote:
> In do_mount() when the MS_* flags are being converted to MNT_* flags,
> MS_RDONLY got accidentally convered to SB_RDONLY.

Applied.

I guess they have the same value (1). How did you notice? Do you have
some patches that turn the kernel flags into a bitwise type? Or did
you just happen on it manually?

           Linus

Re: [PATCH] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion

[Andreas Dilger]

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On Apr 20, 2018, at 11:03 AM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 
> On Fri, Apr 20, 2018 at 5:35 AM, David Howells <dhowells@redhat.com> wrote:
>> In do_mount() when the MS_* flags are being converted to MNT_* flags,
>> MS_RDONLY got accidentally convered to SB_RDONLY.
> 
> Applied.
> 
> I guess they have the same value (1). How did you notice? Do you have
> some patches that turn the kernel flags into a bitwise type? Or did
> you just happen on it manually?

Making s_flags and mnt_flags differently-named enums would help make
this problem more obvious (and some compilers might complain if used
incorrectly).  That also makes it more clear what kind of flags are
being passed to do_mount(), rather than "unsigned long flags".

Even while looking at the code for this, I see that s_flags is being
used incorrectly with MS_* flags all over the place:

static inline bool sb_rdonly(const struct super_block *sb) {
	return sb->s_flags & MS_RDONLY;
}

void inode_add_lru(struct inode *inode)
{
        if (!(inode->i_state & (I_DIRTY_ALL | I_SYNC |
                                I_FREEING | I_WILL_FREE)) &&
            !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
                inode_lru_list_add(inode);
}

A quick grep showed 243 lines matching "->s_flags.*MS_".

Cheers, Andreas






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Re: [PATCH] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion

[David Howells]

Linus Torvalds <torvalds@linux-foundation.org> wrote:

> I guess they have the same value (1). How did you notice? Do you have
> some patches that turn the kernel flags into a bitwise type? Or did
> you just happen on it manually?

I happened to be looking at that bit of code.

They have the saame value for the moment, but this may not always remain so.

David