Messages in this thread | | | Subject | Re: [PATCH] loop: properly observe rotational flag of underlying device | From | Holger Hoffstätte <> | Date | Tue, 26 Mar 2019 17:55:17 +0100 |
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Ping! Jens, can we please let this finally land in 5.2?
thanks, Holger
On 2/12/19 11:54 PM, Benjamin Gordon wrote: > From: Holger Hoffstätte <holger.hoffstaette@googlemail.com> > > The loop driver always declares the rotational flag of its device as > rotational, even when the device of the mapped file is nonrotational, > as is the case with SSDs or on tmpfs. This can confuse filesystem tools > which are SSD-aware; in my case I frequently forget to tell mkfs.btrfs > that my loop device on tmpfs is nonrotational, and that I really don't > need any automatic metadata redundancy. > > The attached patch fixes this by introspecting the rotational flag of the > mapped file's underlying block device, if it exists. If the mapped file's > filesystem has no associated block device - as is the case on e.g. tmpfs - > we assume nonrotational storage. If there is a better way to identify such > non-devices I'd love to hear them. > > Cc: Jens Axboe <axboe@kernel.dk> > Cc: linux-block@vger.kernel.org > Cc: holger@applied-asynchrony.com > Signed-off-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com> > Signed-off-by: Gwendal Grignou <gwendal@chromium.org> > Signed-off-by: Benjamin Gordon <bmgordon@chromium.org> > Reviewed-by: Guenter Roeck <groeck@chromium.org> > --- > This is a resend of Holger's original patch from > https://lkml.org/lkml/2015/11/11/288 with the _unlocked functions > updated. We keep running into the same problem on Chrome OS that this > originally solved; any chance it can go in? > > drivers/block/loop.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index cf5538942834..6c0fc0d49dc0 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -900,6 +900,24 @@ static int loop_prepare_queue(struct loop_device *lo) > return 0; > } > > +static void loop_update_rotational(struct loop_device *lo) > +{ > + struct file *file = lo->lo_backing_file; > + struct inode *file_inode = file->f_mapping->host; > + struct block_device *file_bdev = file_inode->i_sb->s_bdev; > + struct request_queue *q = lo->lo_queue; > + bool nonrot = true; > + > + /* not all filesystems (e.g. tmpfs) have a sb->s_bdev */ > + if (file_bdev) > + nonrot = blk_queue_nonrot(bdev_get_queue(file_bdev)); > + > + if (nonrot) > + blk_queue_flag_set(QUEUE_FLAG_NONROT, q); > + else > + blk_queue_flag_clear(QUEUE_FLAG_NONROT, q); > +} > + > static int loop_set_fd(struct loop_device *lo, fmode_t mode, > struct block_device *bdev, unsigned int arg) > { > @@ -963,6 +981,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, > if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync) > blk_queue_write_cache(lo->lo_queue, true, false); > > + loop_update_rotational(lo); > loop_update_dio(lo); > set_capacity(lo->lo_disk, size); > bd_set_size(bdev, size << 9); >
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