Re: [PATCH 3/5] f2fs: report readonly status in ->fsync

[Chao Yu <chao2.yu@samsung.com>]

> -----Original Message-----
> From: Marc Lehmann [mailto:schmorp@schmorp.de]
> Sent: Saturday, December 26, 2015 2:33 PM
> To: Chao Yu
> Cc: linux-f2fs-devel@lists.sourceforge.net
> Subject: Re: [f2fs-dev] [PATCH 3/5] f2fs: report readonly status in ->fsync
> 
> On Thu, Dec 24, 2015 at 06:07:25PM +0800, Chao Yu <chao2.yu@samsung.com> wrote:
> > Report readonly status of filesystem during fsync.
> 
> If this means that fsync returns EROFS when used on a file on a read-only
> filesystem., then this looks buggy - EROFS is not documented for
> fsync (only as "fd is bound to a special file which does not support
> synchronization") for this condition, and I don't think other filesystems
> do that (just tried xfs).

Yes.

> 
> It also doesn't quite make sense - fsync should only fail when the file
> couldn't be synced, but in most (probably all) cases, the file is already
> synchronised, otherwise the filesystem shouldn't be RO.

Agreed,

One situation here is if '.' or '..' in dentry page of directory inode was
missing (corrupted directory), once fsck found this kind of inode exist in
the image, it will mark inode with F2FS_INLINE_DOTS flag, after that f2fs
will try to recover it to normal one if user touch such inode in ->lookup,
so the dirty data was generated even in a readonly fs.

Actually even for above case, it would be better to avoid generating dirty
data rather than stop user fsync in a readonly fs.

Hi Jaegeuk, could you help to drop this patch?

And one more thing is how do you think of moving inline dot recovery into
fsck?

Thanks,

> 
> I only looked at the diff, so if I missed the context and my reasoning
> doesn't apply, forgive and ignore me :)
> 
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