linux-ext4 - Re: [PATCH v5 1/5] block: Don't invalidate pagecache for invalid falloc modes

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Message-ID: <CAG9=OMMqm6AsdxbGBJJs7DRH-AUtQj8ocC+UJmvVTMMKdVQDnw@mail.gmail.com>
Date:   Wed, 19 Apr 2023 18:48:42 -0700
From:   Sarthak Kukreti <sarthakkukreti@...omium.org>
To:     "Darrick J. Wong" <djwong@...nel.org>
Cc:     dm-devel@...hat.com, linux-block@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Brian Foster <bfoster@...hat.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Bart Van Assche <bvanassche@...gle.com>,
        Daniil Lunev <dlunev@...gle.com>
Subject: Re: [PATCH v5 1/5] block: Don't invalidate pagecache for invalid
 falloc modes

Sorry I tried to be too concise :) Updated with a fixed up patch!

Best
Sarhtak

On Wed, Apr 19, 2023 at 6:22 PM Darrick J. Wong <djwong@...nel.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 devices")
> > Signed-off-by: Sarthak Kukreti <sarthakkukreti@...omium.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, int mode, loff_t start,
> >
> >       filemap_invalidate_lock(inode->i_mapping);
> >
> > -     /* Invalidate the page cache, including dirty pages. */
> > -     error = 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 = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> > +             error = 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 = truncate_bdev_range(...);
>         if (!error)
>                 error = blkdev_issue_zeroout(...);
>
> --D
>
> >                                            len >> SECTOR_SHIFT, GFP_KERNEL,
> >                                            BLKDEV_ZERO_NOUNMAP);
> >               break;
> >       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
> > -             error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> > +             error = truncate_bdev_range(bdev, file->f_mode, start, end) ||
> > +                     blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> >                                            len >> SECTOR_SHIFT, GFP_KERNEL,
> >                                            BLKDEV_ZERO_NOFALLBACK);
> >               break;
> >       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
> > -             error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
> > +             error = truncate_bdev_range(bdev, file->f_mode, start, end) ||
> > +                     blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
> >                                            len >> SECTOR_SHIFT, GFP_KERNEL);
> >               break;
> >       default:
> > --
> > 2.40.0.634.g4ca3ef3211-goog
> >