linux-ext4 - Re: [PATCH 03/12] filemap: update ki_pos in generic_perform

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 Aug 2023 14:56:15 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Matthew Wilcox <willy@...radead.org>, Jens Axboe <axboe@...nel.dk>,
        Xiubo Li <xiubli@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>,
        Christian Brauner <brauner@...nel.org>,
        Theodore Ts'o <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Damien Le Moal <dlemoal@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-block@...r.kernel.org, ceph-devel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-xfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH 03/12] filemap: update ki_pos in generic_perform_write

On Mon, Aug 28, 2023 at 02:32:59PM +0200, Christoph Hellwig wrote:
> On Sun, Aug 27, 2023 at 10:45:18PM +0100, Al Viro wrote:
> > IOW, I suspect that the right thing to do would be something along the lines
> > of
> 
> The idea looks sensible to me, but we'll also need to do it for the
> filemap_write_and_wait_range failure case.

Huh?  That's precisely where this patch is doing that...  That function
in mainline is
        if (unlikely(buffered_written < 0)) {
                if (direct_written)
                        return direct_written;
                return buffered_written;
        }

        /*
         * We need to ensure that the page cache pages are written to disk and
         * invalidated to preserve the expected O_DIRECT semantics.
         */
        err = filemap_write_and_wait_range(mapping, pos, end);
        if (err < 0) {
                /*
                 * We don't know how much we wrote, so just return the number of
                 * bytes which were direct-written
                 */
                if (direct_written)
                        return direct_written;
                return err;
        }
        invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
        return direct_written + buffered_written;

The first failure exit does not need any work - the caller had not bumped
->ki_pos; the second one (after that 'if (err < 0) {' line) does and that's
where the patch upthread adds iocb->ki_pos -= buffered_written.

Or am I completely misparsing what you've written?