Hi,
I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
-LVM2/device mapper doesn't support write barriers
-DRBD uses blkdev_issue_flush() to flush its metadata to disk.
On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
it really does receive an EIO. Promptly, DRBD gives the
error message "drbd0: local disk flush failed with status -5".
The physical disk (in LVM speak) is a RAID1 on a 3ware 9650SE-2LP
controller; the driver 3w-9xxx supports barriers and after moving my D
RBD device from the LV to a single partition on the same RAID1, the
error messages from DRBD vanished.
I've posted a lengty summary of my findings to
http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
... where Lars Ellenberg from DRBD basically responded in
http://lists.linbit.com/pipermail/drbd-user/2008-February/008666.html
... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
2.6.24.2 aparently does return EIO for blkdev_issue_flush.
So simply the question: how should a top-layer driver check wether a lower
device does support barriers? md-raid does check this way differently than
e.g. XFS does, while DRBD also adds a third way to check this.
Or is this "merely" a bug in drivers/md/dm.c?
Anders
--
1&1 Internet AG System Architect
Brauerstrasse 48 v://49.721.91374.50
D-76135 Karlsruhe f://49.721.91374.225
Amtsgericht Montabaur HRB 6484
Vorstand: Henning Ahlert, Ralph Dommermuth, Matthias Ehrlich, Andreas Gauger,
Thomas Gottschlich, Matthias Greve, Robert Hoffmann, Markus Huhn, Achim Weiss
Aufsichtsratsvorsitzender: Michael Scheeren
On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> Hi,
>
> I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
>
> -LVM2/device mapper doesn't support write barriers
> -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
> On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> it really does receive an EIO. Promptly, DRBD gives the
> error message "drbd0: local disk flush failed with status -5".
>
> The physical disk (in LVM speak) is a RAID1 on a 3ware 9650SE-2LP
> controller; the driver 3w-9xxx supports barriers and after moving my D
> RBD device from the LV to a single partition on the same RAID1, the
> error messages from DRBD vanished.
>
> I've posted a lengty summary of my findings to
>
> http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
>
> ... where Lars Ellenberg from DRBD basically responded in
>
> http://lists.linbit.com/pipermail/drbd-user/2008-February/008666.html
>
> ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
>
> So simply the question: how should a top-layer driver check wether a lower
> device does support barriers? md-raid does check this way differently than
> e.g. XFS does, while DRBD also adds a third way to check this.
> Or is this "merely" a bug in drivers/md/dm.c?
>
(cc dm-devel)
I'd say it's a DM bug. Probably a hard-to-fix one though.
On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > -LVM2/device mapper doesn't support write barriers
That's right.
> > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
Which won't work if device-mapper is underneath.
> > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > it really does receive an EIO. Promptly, DRBD gives the
> > error message "drbd0: local disk flush failed with status -5".
> > I've posted a lengty summary of my findings to
> > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> I'd say it's a DM bug.
The dm code is unchanged, but look at the limited endio handling in
ll_rw_blk.c:
static void bio_end_empty_barrier(struct bio *bio, int err)
{
if (err)
clear_bit(BIO_UPTODATE, &bio->bi_flags);
complete(bio->bi_private);
}
int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
{
...
wait_for_completion(&wait);
if (error_sector)
*error_sector = bio->bi_sector;
ret = 0;
if (!bio_flagged(bio, BIO_UPTODATE))
ret = -EIO;
Alasdair
--
[email protected]
On Tue, Feb 26 2008, Alasdair G Kergon wrote:
> On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > > -LVM2/device mapper doesn't support write barriers
>
> That's right.
>
> > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
>
> Which won't work if device-mapper is underneath.
>
> > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > > it really does receive an EIO. Promptly, DRBD gives the
> > > error message "drbd0: local disk flush failed with status -5".
> > > I've posted a lengty summary of my findings to
> > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> > I'd say it's a DM bug.
>
> The dm code is unchanged, but look at the limited endio handling in
> ll_rw_blk.c:
>
> static void bio_end_empty_barrier(struct bio *bio, int err)
> {
> if (err)
> clear_bit(BIO_UPTODATE, &bio->bi_flags);
>
> complete(bio->bi_private);
> }
>
> int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> {
> ...
> wait_for_completion(&wait);
> if (error_sector)
> *error_sector = bio->bi_sector;
> ret = 0;
> if (!bio_flagged(bio, BIO_UPTODATE))
> ret = -EIO;
You are right, the return value got broken there. Does this make it
return -EOPNOTSUPP properly for you?
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 6901eed..55c5f1f 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -259,8 +259,11 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
static void bio_end_empty_barrier(struct bio *bio, int err)
{
- if (err)
+ if (err) {
+ if (err == -EOPNOTSUPP)
+ set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
clear_bit(BIO_UPTODATE, &bio->bi_flags);
+ }
complete(bio->bi_private);
}
@@ -309,7 +312,9 @@ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
*error_sector = bio->bi_sector;
ret = 0;
- if (!bio_flagged(bio, BIO_UPTODATE))
+ if (bio_flagged(bio, BIO_EOPNOTSUPP))
+ ret = -EOPNOTSUPP;
+ else if (!bio_flagged(bio, BIO_UPTODATE))
ret = -EIO;
bio_put(bio);
--
Jens Axboe
On Tue, Feb 26 2008 Jens Axboe wrote:
> On Tue, Feb 26 2008, Alasdair G Kergon wrote:
> > On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> > > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > > > -LVM2/device mapper doesn't support write barriers
> >
> > That's right.
> >
> > > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
> >
> > Which won't work if device-mapper is underneath.
> >
> > > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > > > it really does receive an EIO. Promptly, DRBD gives the
> > > > error message "drbd0: local disk flush failed with status -5".
> > > > I've posted a lengty summary of my findings to
> > > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> > > I'd say it's a DM bug.
> >
> > The dm code is unchanged, but look at the limited endio handling in
> > ll_rw_blk.c:
> >
> > static void bio_end_empty_barrier(struct bio *bio, int err)
> > {
> > if (err)
> > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> >
> > complete(bio->bi_private);
> > }
> >
> > int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> > {
> > ...
> > wait_for_completion(&wait);
> > if (error_sector)
> > *error_sector = bio->bi_sector;
> > ret = 0;
> > if (!bio_flagged(bio, BIO_UPTODATE))
> > ret = -EIO;
>
> You are right, the return value got broken there. Does this make it
> return -EOPNOTSUPP properly for you?
No, it doesn't.
I've applied your patch manually, as 2.6.24.2. doesn't have a "blk-barrier.c":
---cut
--- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11
06:51:11.000000000 +0100
+++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:02:28.514641620
+0100
@@ -2667,8 +2667,11 @@
static void bio_end_empty_barrier(struct bio *bio, int err)
{
- if (err)
+ if (err) {
+ if (err == -EOPNOTSUPP)
+ set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
clear_bit(BIO_UPTODATE, &bio->bi_flags);
+ }
complete(bio->bi_private);
}
---cut
... and the resulting kernel shows exactly the same behaviour than before:
[ 752.301388] drbd0: Writing meta data super block now.
[ 752.349713] drbd0: local disk flush failed with status -5
[ 752.416256] drbd0: local disk flush failed with status -5
[ 753.419254] drbd0: local disk flush failed with status -5
[ 753.925726] drbd0: local disk flush failed with status -5
[ 754.551176] drbd0: local disk flush failed with status -5
[ 754.806052] drbd0: local disk flush failed with status -5
[ 755.327988] drbd0: local disk flush failed with status -5
[ 755.781863] drbd0: local disk flush failed with status -5
[ 756.266694] drbd0: local disk flush failed with status -5
Anders
> diff --git a/block/blk-barrier.c b/block/blk-barrier.c
> index 6901eed..55c5f1f 100644
> --- a/block/blk-barrier.c
> +++ b/block/blk-barrier.c
> @@ -259,8 +259,11 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
>
> static void bio_end_empty_barrier(struct bio *bio, int err)
> {
> - if (err)
> + if (err) {
> + if (err == -EOPNOTSUPP)
> + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
> clear_bit(BIO_UPTODATE, &bio->bi_flags);
> + }
>
> complete(bio->bi_private);
> }
> @@ -309,7 +312,9 @@ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> *error_sector = bio->bi_sector;
>
> ret = 0;
> - if (!bio_flagged(bio, BIO_UPTODATE))
> + if (bio_flagged(bio, BIO_EOPNOTSUPP))
> + ret = -EOPNOTSUPP;
> + else if (!bio_flagged(bio, BIO_UPTODATE))
> ret = -EIO;
>
> bio_put(bio);
>
> --
> Jens Axboe
>
--
1&1 Internet AG "Use the --force, Luke"
Brauerstrasse 48 v://49.721.91374.50
D-76135 Karlsruhe f://49.721.91374.225
Amtsgericht Montabaur HRB 6484
Vorstand: Henning Ahlert, Ralph Dommermuth, Matthias Ehrlich, Andreas Gauger,
Thomas Gottschlich, Matthias Greve, Robert Hoffmann, Markus Huhn, Achim Weiss
Aufsichtsratsvorsitzender: Michael Scheeren
On Tue, Feb 26 2008, Anders Henke wrote:
> On Tue, Feb 26 2008 Jens Axboe wrote:
> > On Tue, Feb 26 2008, Alasdair G Kergon wrote:
> > > On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> > > > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > > > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > > > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > > > > -LVM2/device mapper doesn't support write barriers
> > >
> > > That's right.
> > >
> > > > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
> > >
> > > Which won't work if device-mapper is underneath.
> > >
> > > > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > > > > it really does receive an EIO. Promptly, DRBD gives the
> > > > > error message "drbd0: local disk flush failed with status -5".
> > > > > I've posted a lengty summary of my findings to
> > > > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > > > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > > > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> > > > I'd say it's a DM bug.
> > >
> > > The dm code is unchanged, but look at the limited endio handling in
> > > ll_rw_blk.c:
> > >
> > > static void bio_end_empty_barrier(struct bio *bio, int err)
> > > {
> > > if (err)
> > > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > >
> > > complete(bio->bi_private);
> > > }
> > >
> > > int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> > > {
> > > ...
> > > wait_for_completion(&wait);
> > > if (error_sector)
> > > *error_sector = bio->bi_sector;
> > > ret = 0;
> > > if (!bio_flagged(bio, BIO_UPTODATE))
> > > ret = -EIO;
> >
> > You are right, the return value got broken there. Does this make it
> > return -EOPNOTSUPP properly for you?
>
>
> No, it doesn't.
>
>
>
> I've applied your patch manually, as 2.6.24.2. doesn't have a "blk-barrier.c":
>
> ---cut
> --- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11
> 06:51:11.000000000 +0100
> +++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:02:28.514641620
> +0100
> @@ -2667,8 +2667,11 @@
>
> static void bio_end_empty_barrier(struct bio *bio, int err)
> {
> - if (err)
> + if (err) {
> + if (err == -EOPNOTSUPP)
> + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
> clear_bit(BIO_UPTODATE, &bio->bi_flags);
> + }
>
> complete(bio->bi_private);
> }
> ---cut
>
> ... and the resulting kernel shows exactly the same behaviour than before:
Not surprising, as you missed half of the patch:
> > @@ -309,7 +312,9 @@ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> > *error_sector = bio->bi_sector;
> >
> > ret = 0;
> > - if (!bio_flagged(bio, BIO_UPTODATE))
> > + if (bio_flagged(bio, BIO_EOPNOTSUPP))
> > + ret = -EOPNOTSUPP;
> > + else if (!bio_flagged(bio, BIO_UPTODATE))
> > ret = -EIO;
> >
> > bio_put(bio);
--
Jens Axboe
On Tue, Feb 26 2008 schrieb Jens Axboe:
> On Tue, Feb 26 2008, Anders Henke wrote:
> > On Tue, Feb 26 2008 Jens Axboe wrote:
> > > On Tue, Feb 26 2008, Alasdair G Kergon wrote:
> > > > On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> > > > > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > > > > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > > > > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > > > > > -LVM2/device mapper doesn't support write barriers
> > > >
> > > > That's right.
> > > >
> > > > > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
> > > >
> > > > Which won't work if device-mapper is underneath.
> > > >
> > > > > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > > > > > it really does receive an EIO. Promptly, DRBD gives the
> > > > > > error message "drbd0: local disk flush failed with status -5".
> > > > > > I've posted a lengty summary of my findings to
> > > > > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > > > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > > > > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > > > > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> > > > > I'd say it's a DM bug.
> > > >
> > > > The dm code is unchanged, but look at the limited endio handling in
> > > > ll_rw_blk.c:
> > > >
> > > > static void bio_end_empty_barrier(struct bio *bio, int err)
> > > > {
> > > > if (err)
> > > > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > > >
> > > > complete(bio->bi_private);
> > > > }
> > > >
> > > > int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> > > > {
> > > > ...
> > > > wait_for_completion(&wait);
> > > > if (error_sector)
> > > > *error_sector = bio->bi_sector;
> > > > ret = 0;
> > > > if (!bio_flagged(bio, BIO_UPTODATE))
> > > > ret = -EIO;
> > >
> > > You are right, the return value got broken there. Does this make it
> > > return -EOPNOTSUPP properly for you?
> >
> >
> > No, it doesn't.
> >
> >
> >
> > I've applied your patch manually, as 2.6.24.2. doesn't have a "blk-barrier.c":
> >
> > ---cut
> > --- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11
> > 06:51:11.000000000 +0100
> > +++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:02:28.514641620
> > +0100
> > @@ -2667,8 +2667,11 @@
> >
> > static void bio_end_empty_barrier(struct bio *bio, int err)
> > {
> > - if (err)
> > + if (err) {
> > + if (err == -EOPNOTSUPP)
> > + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
> > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > + }
> >
> > complete(bio->bi_private);
> > }
> > ---cut
> >
> > ... and the resulting kernel shows exactly the same behaviour than before:
>
> Not surprising, as you missed half of the patch:
Ouch. Thank you for pointing this out.
I've been spending too much time of the day with things who have a negative
impact on my concentration and I shouldn't manually patch kernels at
this time of the day.
Yes, it's useless to set a bit, but never check it (like in my version of
your patch).
After adding the second part of your patch, the resulting kernel works as
intended:
[ 234.946192] drbd0: conn( WFSyncUUID -> SyncTarget )
[ 234.956176] drbd0: Began resync as SyncTarget (will sync 19542404 KB
[4885601
bits set]).
[ 234.972567] drbd0: Writing meta data super block now.
[ 235.018203] drbd0: local disk flush failed with status -95
DRBD sees the EOPNOTSUPP, logs this message only once and doesn't try
any further barrier requests (as intended).
Just for the records, the 2.6.24.2-ready version of your patch:
---cut
--- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11 06:51:11.000000000 +0
100
+++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:58:05.552467940 +0100
@@ -2667,8 +2667,11 @@
static void bio_end_empty_barrier(struct bio *bio, int err)
{
- if (err)
+ if (err) {
+ if (err == -EOPNOTSUPP)
+ set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
clear_bit(BIO_UPTODATE, &bio->bi_flags);
+ }
complete(bio->bi_private);
}
@@ -2717,7 +2720,9 @@
*error_sector = bio->bi_sector;
ret = 0;
- if (!bio_flagged(bio, BIO_UPTODATE))
+ if (bio_flagged(bio, BIO_EOPNOTSUPP))
+ ret = -EOPNOTSUPP;
+ else if (!bio_flagged(bio, BIO_UPTODATE))
ret = -EIO;
bio_put(bio);
---cut
Anders
--
1&1 Internet AG better sleep(28800)
Brauerstrasse 48 v://49.721.91374.50
D-76135 Karlsruhe f://49.721.91374.225
Amtsgericht Montabaur HRB 6484
Vorstand: Henning Ahlert, Ralph Dommermuth, Matthias Ehrlich, Andreas Gauger,
Thomas Gottschlich, Matthias Greve, Robert Hoffmann, Markus Huhn, Achim Weiss
Aufsichtsratsvorsitzender: Michael Scheeren
On Tue, Feb 26 2008, Anders Henke wrote:
> On Tue, Feb 26 2008 schrieb Jens Axboe:
> > On Tue, Feb 26 2008, Anders Henke wrote:
> > > On Tue, Feb 26 2008 Jens Axboe wrote:
> > > > On Tue, Feb 26 2008, Alasdair G Kergon wrote:
> > > > > On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote:
> > > > > > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <[email protected]> wrote:
> > > > > > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
> > > > > > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV).
> > > > > > > -LVM2/device mapper doesn't support write barriers
> > > > >
> > > > > That's right.
> > > > >
> > > > > > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
> > > > >
> > > > > Which won't work if device-mapper is underneath.
> > > > >
> > > > > > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
> > > > > > > it really does receive an EIO. Promptly, DRBD gives the
> > > > > > > error message "drbd0: local disk flush failed with status -5".
> > > > > > > I've posted a lengty summary of my findings to
> > > > > > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > > > > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
> > > > > > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
> > > > > > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush.
> > > > > > I'd say it's a DM bug.
> > > > >
> > > > > The dm code is unchanged, but look at the limited endio handling in
> > > > > ll_rw_blk.c:
> > > > >
> > > > > static void bio_end_empty_barrier(struct bio *bio, int err)
> > > > > {
> > > > > if (err)
> > > > > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > > > >
> > > > > complete(bio->bi_private);
> > > > > }
> > > > >
> > > > > int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
> > > > > {
> > > > > ...
> > > > > wait_for_completion(&wait);
> > > > > if (error_sector)
> > > > > *error_sector = bio->bi_sector;
> > > > > ret = 0;
> > > > > if (!bio_flagged(bio, BIO_UPTODATE))
> > > > > ret = -EIO;
> > > >
> > > > You are right, the return value got broken there. Does this make it
> > > > return -EOPNOTSUPP properly for you?
> > >
> > >
> > > No, it doesn't.
> > >
> > >
> > >
> > > I've applied your patch manually, as 2.6.24.2. doesn't have a "blk-barrier.c":
> > >
> > > ---cut
> > > --- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11
> > > 06:51:11.000000000 +0100
> > > +++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:02:28.514641620
> > > +0100
> > > @@ -2667,8 +2667,11 @@
> > >
> > > static void bio_end_empty_barrier(struct bio *bio, int err)
> > > {
> > > - if (err)
> > > + if (err) {
> > > + if (err == -EOPNOTSUPP)
> > > + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
> > > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > > + }
> > >
> > > complete(bio->bi_private);
> > > }
> > > ---cut
> > >
> > > ... and the resulting kernel shows exactly the same behaviour than before:
> >
> > Not surprising, as you missed half of the patch:
>
> Ouch. Thank you for pointing this out.
>
> I've been spending too much time of the day with things who have a negative
> impact on my concentration and I shouldn't manually patch kernels at
> this time of the day.
>
> Yes, it's useless to set a bit, but never check it (like in my version of
> your patch).
>
> After adding the second part of your patch, the resulting kernel works as
> intended:
>
> [ 234.946192] drbd0: conn( WFSyncUUID -> SyncTarget )
> [ 234.956176] drbd0: Began resync as SyncTarget (will sync 19542404 KB
> [4885601
> bits set]).
> [ 234.972567] drbd0: Writing meta data super block now.
> [ 235.018203] drbd0: local disk flush failed with status -95
>
> DRBD sees the EOPNOTSUPP, logs this message only once and doesn't try
> any further barrier requests (as intended).
OK good, that's what I expected :-)
I'll queue the patch for 2.6.25, the 2.6.24 should go to stable. Send me
a properly formatted patch and I'll make sure it goes that way.
Thanks for testing!
--
Jens Axboe
On Feb 26 2008, Jens Axboe wrote:
> > [ 234.946192] drbd0: conn( WFSyncUUID -> SyncTarget )
> > [ 234.956176] drbd0: Began resync as SyncTarget (will sync 19542404 KB
> > [4885601
> > bits set]).
> > [ 234.972567] drbd0: Writing meta data super block now.
> > [ 235.018203] drbd0: local disk flush failed with status -95
> >
> > DRBD sees the EOPNOTSUPP, logs this message only once and doesn't try
> > any further barrier requests (as intended).
>
> OK good, that's what I expected :-)
>
> I'll queue the patch for 2.6.25, the 2.6.24 should go to stable. Send me
> a properly formatted patch and I'll make sure it goes that way.
>
> Thanks for testing!
'diff -up''d patch is attached.
Anders
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