On Mar 09, 2021 / 17:28, Kanchan Joshi wrote:
> On Tue, Mar 9, 2021 at 4:36 PM Damien Le Moal <Damien.LeMoal@xxxxxxx> wrote:
> >
> > On 2021/03/09 14:49, Kanchan Joshi wrote:
> > > On Mon, Mar 8, 2021 at 2:11 PM Shin'ichiro Kawasaki
> > > <shinichiro.kawasaki@xxxxxxx> wrote:
> > >>
> > >> When zone reset ioctl and data read race for a same zone on zoned block
> > >> devices, the data read leaves stale page cache even though the zone
> > >> reset ioctl zero clears all the zone data on the device. To avoid
> > >> non-zero data read from the stale page cache after zone reset, discard
> > >> page cache of reset target zones. In same manner as fallocate, call the
> > >> function truncate_bdev_range() in blkdev_zone_mgmt_ioctl() before and
> > >> after zone reset to ensure the page cache discarded.
> > >>
> > >> This patch can be applied back to the stable kernel version v5.10.y.
> > >> Rework is needed for older stable kernels.
> > >>
> > >> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> > >> Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
> > >> Cc: <stable@xxxxxxxxxxxxxxx> # 5.10+
> > >> ---
> > >> block/blk-zoned.c | 30 ++++++++++++++++++++++++++++--
> > >> 1 file changed, 28 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> > >> index 833978c02e60..990a36be2927 100644
> > >> --- a/block/blk-zoned.c
> > >> +++ b/block/blk-zoned.c
> > >> @@ -329,6 +329,9 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> > >> struct request_queue *q;
> > >> struct blk_zone_range zrange;
> > >> enum req_opf op;
> > >> + sector_t capacity;
> > >> + loff_t start, end;
> > >> + int ret;
> > >>
> > >> if (!argp)
> > >> return -EINVAL;
> > >> @@ -349,9 +352,22 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> > >> if (copy_from_user(&zrange, argp, sizeof(struct blk_zone_range)))
> > >> return -EFAULT;
> > >>
> > >> + capacity = get_capacity(bdev->bd_disk);
> > >> + if (zrange.sector + zrange.nr_sectors <= zrange.sector ||
> > >> + zrange.sector + zrange.nr_sectors > capacity)
> > >> + /* Out of range */
> > >> + return -EINVAL;
> > >> +
> > >> + start = zrange.sector << SECTOR_SHIFT;
> > >> + end = ((zrange.sector + zrange.nr_sectors) << SECTOR_SHIFT) - 1;
> > >
> > > How about doing all this calculation only when it is applicable i.e.
> > > only for reset-zone case, and not for other cases (open/close/finish
> > > zone).
> > >
> > > Also apart from "out of range" (which is covered here), there are few
> > > more cases when blkdev_zone_mgmt() may fail it (not covered here).
> > > Perhaps the whole pre and post truncate part can fit better inside
> > > blkdev_zone_mgmt itself.
> >
> > No, I do not think so. That would add overhead for in-kernel users of zone reset
> > for no good reason since these would typically take care of cached pages
> > themselves (e.g. FS) and would not trigger page caching using the bdev inode anyway.
>
> Agreed. In that case moving the pre-truncate processing from
> common-path to under BLKRESETZONE will suffice.
> With that refactoring in place, it looks good.
>
> Reviewed-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
Thanks. Will reflect your comment and the other comment by Damien for v2.
--
Best Regards,
Shin'ichiro Kawasaki
