From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mandeep Singh Baines Subject: Re: [PATCH 3/3] vfs: change sb->s_maxbytes to a loff_t Date: Mon, 10 Aug 2009 14:24:48 -0700 Message-ID: <20090810212447.GC10147@google.com> References: <1249906663-7572-1-git-send-email-jlayton@redhat.com> <1249906663-7572-4-git-send-email-jlayton@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hch@infradead.org, rlove@google.com, viro@zeniv.linux.org.uk, hannes@cmpxchg.org To: Jeff Layton Return-path: Received: from smtp-out.google.com ([216.239.33.17]:57989 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753138AbZHJVY7 (ORCPT ); Mon, 10 Aug 2009 17:24:59 -0400 Content-Disposition: inline In-Reply-To: <1249906663-7572-4-git-send-email-jlayton@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Jeff Layton (jlayton@redhat.com) wrote: > sb->s_maxbytes is supposed to indicate the maximum size of a file that > can exist on the filesystem. It's declared as an unsigned long long. > > Even if a filesystem has no inherent limit that prevents it from using > every bit in that unsigned long long, it's still problematic to set it > to anything larger than MAX_LFS_FILESIZE. There are places in the kernel > that cast s_maxbytes to a signed value. If it's set too large then this > cast makes it a negative number and generally breaks the comparison. > > Change s_maxbytes to be loff_t instead. That should help eliminate the > temptation to set it too large by making it a signed value. > > Also, add a warning for couple of releases to help catch filesystems > that set s_maxbytes too large. Eventually we can either convert this to > a BUG() or just remove it and in the hope that no one will get it wrong > now that it's a signed value. > > Signed-off-by: Jeff Layton > --- > fs/super.c | 10 ++++++++++ > include/linux/fs.h | 2 +- > 2 files changed, 11 insertions(+), 1 deletions(-) > > diff --git a/fs/super.c b/fs/super.c > index 2761d3e..660d437 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -889,6 +889,16 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void > if (error) > goto out_sb; > > + /* > + * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE > + * but s_maxbytes was an unsigned long long for many releases. Throw > + * this warning for a little while to try and catch filesystems that > + * violate this rule. This warning should be either removed or > + * converted to a BUG() in 2.6.34. > + */ > + WARN((mnt->mnt_sb->s_maxbytes < 0), "WARNING: %s set sb->s_maxbytes to " > + "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes); > + Minor nit. "WARNING:" is redundant. I believe WARN() will already print "WARNING: at :". > mnt->mnt_mountpoint = mnt->mnt_root; > mnt->mnt_parent = mnt; > up_write(&mnt->mnt_sb->s_umount); > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 67888a9..bfe3c08 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1316,7 +1316,7 @@ struct super_block { > unsigned long s_blocksize; > unsigned char s_blocksize_bits; > unsigned char s_dirt; > - unsigned long long s_maxbytes; /* Max file size */ > + loff_t s_maxbytes; /* Max file size */ Looks good to me. Thanks! > struct file_system_type *s_type; > const struct super_operations *s_op; > struct dquot_operations *dq_op; > -- > 1.6.0.6 >