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From:   Sarthak Kukreti <sarthakkukreti@chromium.org>
Date:   Wed, 19 Apr 2023 18:48:42 -0700
Message-ID: <CAG9=OMMqm6AsdxbGBJJs7DRH-AUtQj8ocC+UJmvVTMMKdVQDnw@mail.gmail.com>
Subject: Re: [PATCH v5 1/5] block: Don't invalidate pagecache for invalid
 falloc modes
To:     "Darrick J. Wong" <djwong@kernel.org>
Cc:     dm-devel@redhat.com, linux-block@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Brian Foster <bfoster@redhat.com>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Bart Van Assche <bvanassche@google.com>,
        Daniil Lunev <dlunev@google.com>
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Sorry I tried to be too concise :) Updated with a fixed up patch!

Best
Sarhtak

On Wed, Apr 19, 2023 at 6:22=E2=80=AFPM Darrick J. Wong <djwong@kernel.org>=
 wrote:
>
> On Wed, Apr 19, 2023 at 05:48:46PM -0700, Sarthak Kukreti wrote:
> > Only call truncate_bdev_range() if the fallocate mode is
> > supported. This fixes a bug where data in the pagecache
> > could be invalidated if the fallocate() was called on the
> > block device with an invalid mode.
> >
> > Fixes: 25f4c41415e5 ("block: implement (some of) fallocate for block de=
vices")
> > Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
> > ---
> >  block/fops.c | 18 ++++++++++--------
> >  1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/block/fops.c b/block/fops.c
> > index d2e6be4e3d1c..2fd7e8b9ab48 100644
> > --- a/block/fops.c
> > +++ b/block/fops.c
> > @@ -648,25 +648,27 @@ static long blkdev_fallocate(struct file *file, i=
nt mode, loff_t start,
> >
> >       filemap_invalidate_lock(inode->i_mapping);
> >
> > -     /* Invalidate the page cache, including dirty pages. */
> > -     error =3D truncate_bdev_range(bdev, file->f_mode, start, end);
> > -     if (error)
> > -             goto fail;
> > -
> > +     /*
> > +      * Invalidate the page cache, including dirty pages, for valid
> > +      * de-allocate mode calls to fallocate().
> > +      */
> >       switch (mode) {
> >       case FALLOC_FL_ZERO_RANGE:
> >       case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
> > -             error =3D blkdev_issue_zeroout(bdev, start >> SECTOR_SHIF=
T,
> > +             error =3D truncate_bdev_range(bdev, file->f_mode, start, =
end) ||
> > +                     blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
>
> I'm pretty sure we're supposed to preserve the error codes returned by
> both functions.
>
>         error =3D truncate_bdev_range(...);
>         if (!error)
>                 error =3D blkdev_issue_zeroout(...);
>
> --D
>
> >                                            len >> SECTOR_SHIFT, GFP_KER=
NEL,
> >                                            BLKDEV_ZERO_NOUNMAP);
> >               break;
> >       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
> > -             error =3D blkdev_issue_zeroout(bdev, start >> SECTOR_SHIF=
T,
> > +             error =3D truncate_bdev_range(bdev, file->f_mode, start, =
end) ||
> > +                     blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> >                                            len >> SECTOR_SHIFT, GFP_KER=
NEL,
> >                                            BLKDEV_ZERO_NOFALLBACK);
> >               break;
> >       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HI=
DE_STALE:
> > -             error =3D blkdev_issue_discard(bdev, start >> SECTOR_SHIF=
T,
> > +             error =3D truncate_bdev_range(bdev, file->f_mode, start, =
end) ||
> > +                     blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
> >                                            len >> SECTOR_SHIFT, GFP_KER=
NEL);
> >               break;
> >       default:
> > --
> > 2.40.0.634.g4ca3ef3211-goog
> >