<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/drivers/block, branch v3.10.63</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>sunvdc: don't call VD_OP_GET_VTOC</title>
<updated>2014-11-21T17:22:52+00:00</updated>
<author>
<name>Dwight Engen</name>
<email>dwight.engen@oracle.com</email>
</author>
<published>2014-10-30T19:55:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=df6329d2eb252866542b9efaef34b2e0d777e649'/>
<id>df6329d2eb252866542b9efaef34b2e0d777e649</id>
<content type='text'>
[ Upstream commit 85b0c6e62c48bb9179fd5b3e954f362fb346cbd5 ]

The VD_OP_GET_VTOC operation will succeed only if the vdisk backend has a
VTOC label, otherwise it will fail. In particular, it will return error
48 (ENOTSUP) if the disk has an EFI label. VTOC disk labels are already
handled by directly reading the disk in block/partitions/sun.c (enabled by
CONFIG_SUN_PARTITION which defaults to y on SPARC). Since port-&gt;label is
unused in the driver, remove the call and the field.

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 85b0c6e62c48bb9179fd5b3e954f362fb346cbd5 ]

The VD_OP_GET_VTOC operation will succeed only if the vdisk backend has a
VTOC label, otherwise it will fail. In particular, it will return error
48 (ENOTSUP) if the disk has an EFI label. VTOC disk labels are already
handled by directly reading the disk in block/partitions/sun.c (enabled by
CONFIG_SUN_PARTITION which defaults to y on SPARC). Since port-&gt;label is
unused in the driver, remove the call and the field.

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>vio: fix reuse of vio_dring slot</title>
<updated>2014-11-21T17:22:52+00:00</updated>
<author>
<name>Dwight Engen</name>
<email>dwight.engen@oracle.com</email>
</author>
<published>2014-09-19T13:43:02+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=891b60578feb65bdc55b69948ce98fea7ca88b1f'/>
<id>891b60578feb65bdc55b69948ce98fea7ca88b1f</id>
<content type='text'>
[ Upstream commit d0aedcd4f14a22e23b313f42b7e6e6ebfc0fbc31 ]

vio_dring_avail() will allow use of every dring entry, but when the last
entry is allocated then dr-&gt;prod == dr-&gt;cons which is indistinguishable from
the ring empty condition. This causes the next allocation to reuse an entry.
When this happens in sunvdc, the server side vds driver begins nack'ing the
messages and ends up resetting the ldc channel. This problem does not effect
sunvnet since it checks for &lt; 2.

The fix here is to just never allocate the very last dring slot so that full
and empty are not the same condition. The request start path was changed to
check for the ring being full a bit earlier, and to stop the blk_queue if
there is no space left. The blk_queue will be restarted once the ring is
only half full again. The number of ring entries was increased to 512 which
matches the sunvnet and Solaris vdc drivers, and greatly reduces the
frequency of hitting the ring full condition and the associated blk_queue
stop/starting. The checks in sunvent were adjusted to account for
vio_dring_avail() returning 1 less.

Orabug: 19441666
OraBZ: 14983

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit d0aedcd4f14a22e23b313f42b7e6e6ebfc0fbc31 ]

vio_dring_avail() will allow use of every dring entry, but when the last
entry is allocated then dr-&gt;prod == dr-&gt;cons which is indistinguishable from
the ring empty condition. This causes the next allocation to reuse an entry.
When this happens in sunvdc, the server side vds driver begins nack'ing the
messages and ends up resetting the ldc channel. This problem does not effect
sunvnet since it checks for &lt; 2.

The fix here is to just never allocate the very last dring slot so that full
and empty are not the same condition. The request start path was changed to
check for the ring being full a bit earlier, and to stop the blk_queue if
there is no space left. The blk_queue will be restarted once the ring is
only half full again. The number of ring entries was increased to 512 which
matches the sunvnet and Solaris vdc drivers, and greatly reduces the
frequency of hitting the ring full condition and the associated blk_queue
stop/starting. The checks in sunvent were adjusted to account for
vio_dring_avail() returning 1 less.

Orabug: 19441666
OraBZ: 14983

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sunvdc: limit each sg segment to a page</title>
<updated>2014-11-21T17:22:52+00:00</updated>
<author>
<name>Dwight Engen</name>
<email>dwight.engen@oracle.com</email>
</author>
<published>2014-09-19T13:42:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5cf61378accedc6acd5923f3b00bc945be1a9d29'/>
<id>5cf61378accedc6acd5923f3b00bc945be1a9d29</id>
<content type='text'>
[ Upstream commit 5eed69ffd248c9f68f56c710caf07db134aef28b ]

ldc_map_sg() could fail its check that the number of pages referred to
by the sg scatterlist was &lt;= the number of cookies.

This fixes the issue by doing a similar thing to the xen-blkfront driver,
ensuring that the scatterlist will only ever contain a segment count &lt;=
port-&gt;ring_cookies, and each segment will be page aligned, and &lt;= page
size. This ensures that the scatterlist is always mappable.

Orabug: 19347817
OraBZ: 15945

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 5eed69ffd248c9f68f56c710caf07db134aef28b ]

ldc_map_sg() could fail its check that the number of pages referred to
by the sg scatterlist was &lt;= the number of cookies.

This fixes the issue by doing a similar thing to the xen-blkfront driver,
ensuring that the scatterlist will only ever contain a segment count &lt;=
port-&gt;ring_cookies, and each segment will be page aligned, and &lt;= page
size. This ensures that the scatterlist is always mappable.

Orabug: 19347817
OraBZ: 15945

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sunvdc: compute vdisk geometry from capacity</title>
<updated>2014-11-21T17:22:52+00:00</updated>
<author>
<name>Allen Pais</name>
<email>allen.pais@oracle.com</email>
</author>
<published>2014-09-19T13:42:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=9e23c21149bfdc57aa9d9a35821994dfb0253c40'/>
<id>9e23c21149bfdc57aa9d9a35821994dfb0253c40</id>
<content type='text'>
[ Upstream commit de5b73f08468b4fc5e2f6d1505f650262622f78b ]

The LDom diskserver doesn't return reliable geometry data. In addition,
the types for all fields in the vio_disk_geom are u16, which were being
truncated in the cast into the u8's of the Linux struct hd_geometry.

Modify vdc_getgeo() to compute the geometry from the disk's capacity in a
manner consistent with xen-blkfront::blkif_getgeo().

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit de5b73f08468b4fc5e2f6d1505f650262622f78b ]

The LDom diskserver doesn't return reliable geometry data. In addition,
the types for all fields in the vio_disk_geom are u16, which were being
truncated in the cast into the u8's of the Linux struct hd_geometry.

Modify vdc_getgeo() to compute the geometry from the disk's capacity in a
manner consistent with xen-blkfront::blkif_getgeo().

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sunvdc: add cdrom and v1.1 protocol support</title>
<updated>2014-11-21T17:22:52+00:00</updated>
<author>
<name>Allen Pais</name>
<email>allen.pais@oracle.com</email>
</author>
<published>2014-09-19T13:42:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e4da88a6dab26f68c5f0e493178f9ef2c23f0d08'/>
<id>e4da88a6dab26f68c5f0e493178f9ef2c23f0d08</id>
<content type='text'>
[ Upstream commit 9bce21828d54a95143f1b74619705c2dd8e88b92 ]

Interpret the media type from v1.1 protocol to support CDROM/DVD.

For v1.0 protocol, a disk's size continues to be calculated from the
geometry returned by the vdisk server. The geometry returned by the server
can be less than the actual number of sectors available in the backing
image/device due to the rounding in the division used to compute the
geometry in the vdisk server.

In v1.1 protocol a disk's actual size in sectors is returned during the
handshake. Use this size when v1.1 protocol is negotiated. Since this size
will always be larger than the former geometry computed size, disks created
under v1.0 will be forwards compatible to v1.1, but not vice versa.

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 9bce21828d54a95143f1b74619705c2dd8e88b92 ]

Interpret the media type from v1.1 protocol to support CDROM/DVD.

For v1.0 protocol, a disk's size continues to be calculated from the
geometry returned by the vdisk server. The geometry returned by the server
can be less than the actual number of sectors available in the backing
image/device due to the rounding in the division used to compute the
geometry in the vdisk server.

In v1.1 protocol a disk's actual size in sectors is returned during the
handshake. Use this size when v1.1 protocol is negotiated. Since this size
will always be larger than the former geometry computed size, disks created
under v1.0 will be forwards compatible to v1.1, but not vice versa.

Signed-off-by: Dwight Engen &lt;dwight.engen@oracle.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: Fix error recovery in rbd_obj_read_sync()</title>
<updated>2014-11-14T16:48:00+00:00</updated>
<author>
<name>Jan Kara</name>
<email>jack@suse.cz</email>
</author>
<published>2014-10-22T07:17:24+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=f693fddf24d1808a835b15c72c04d30c2df1e6e7'/>
<id>f693fddf24d1808a835b15c72c04d30c2df1e6e7</id>
<content type='text'>
commit a8d4205623ae965e36c68629db306ca0695a2771 upstream.

When we fail to allocate page vector in rbd_obj_read_sync() we just
basically ignore the problem and continue which will result in an oops
later. Fix the problem by returning proper error.

CC: Yehuda Sadeh &lt;yehuda@inktank.com&gt;
CC: Sage Weil &lt;sage@inktank.com&gt;
CC: ceph-devel@vger.kernel.org
Coverity-id: 1226882
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit a8d4205623ae965e36c68629db306ca0695a2771 upstream.

When we fail to allocate page vector in rbd_obj_read_sync() we just
basically ignore the problem and continue which will result in an oops
later. Fix the problem by returning proper error.

CC: Yehuda Sadeh &lt;yehuda@inktank.com&gt;
CC: Sage Weil &lt;sage@inktank.com&gt;
CC: ceph-devel@vger.kernel.org
Coverity-id: 1226882
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>drbd: compute the end before rb_insert_augmented()</title>
<updated>2014-11-14T16:47:55+00:00</updated>
<author>
<name>Lai Jiangshan</name>
<email>laijs@cn.fujitsu.com</email>
</author>
<published>2014-09-18T14:49:41+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=29772e3e199f2c13cd5f00694e633fb80bbb0415'/>
<id>29772e3e199f2c13cd5f00694e633fb80bbb0415</id>
<content type='text'>
commit 82cfb90bc99d7b7e0ec62d0505b9d4f06805d5db upstream.

Commit 98683650 "Merge branch 'drbd-8.4_ed6' into
for-3.8-drivers-drbd-8.4_ed6" switches to the new augment API, but the
new API requires that the tree is augmented before rb_insert_augmented()
is called, which is missing.

So we add the augment-code to drbd_insert_interval() when it travels the
tree up to down before rb_insert_augmented().  See the example in
include/linux/interval_tree_generic.h or Documentation/rbtree.txt.

drbd_insert_interval() may cancel the insertion when traveling, in this
case, the just added augment-code does nothing before cancel since the
@this node is already in the subtrees in this case.

CC: Michel Lespinasse &lt;walken@google.com&gt;
Signed-off-by: Lai Jiangshan &lt;laijs@cn.fujitsu.com&gt;
Signed-off-by: Andreas Gruenbacher &lt;agruen@linbit.com&gt;
Signed-off-by: Philipp Reisner &lt;philipp.reisner@linbit.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 82cfb90bc99d7b7e0ec62d0505b9d4f06805d5db upstream.

Commit 98683650 "Merge branch 'drbd-8.4_ed6' into
for-3.8-drivers-drbd-8.4_ed6" switches to the new augment API, but the
new API requires that the tree is augmented before rb_insert_augmented()
is called, which is missing.

So we add the augment-code to drbd_insert_interval() when it travels the
tree up to down before rb_insert_augmented().  See the example in
include/linux/interval_tree_generic.h or Documentation/rbtree.txt.

drbd_insert_interval() may cancel the insertion when traveling, in this
case, the just added augment-code does nothing before cancel since the
@this node is already in the subtrees in this case.

CC: Michel Lespinasse &lt;walken@google.com&gt;
Signed-off-by: Lai Jiangshan &lt;laijs@cn.fujitsu.com&gt;
Signed-off-by: Andreas Gruenbacher &lt;agruen@linbit.com&gt;
Signed-off-by: Philipp Reisner &lt;philipp.reisner@linbit.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>drbd: fix regression 'out of mem, failed to invoke fence-peer helper'</title>
<updated>2014-10-09T19:18:43+00:00</updated>
<author>
<name>Lars Ellenberg</name>
<email>lars.ellenberg@linbit.com</email>
</author>
<published>2014-07-09T19:18:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6353c97aa7c7dd6b0c3fe717eeacb39e3873259e'/>
<id>6353c97aa7c7dd6b0c3fe717eeacb39e3873259e</id>
<content type='text'>
commit bbc1c5e8ad6dfebf9d13b8a4ccdf66c92913eac9 upstream.

Since linux kernel 3.13, kthread_run() internally uses
wait_for_completion_killable().  We sometimes may use kthread_run()
while we still have a signal pending, which we used to kick our threads
out of potentially blocking network functions, causing kthread_run() to
mistake that as a new fatal signal and fail.

Fix: flush_signals() before kthread_run().

Signed-off-by: Philipp Reisner &lt;philipp.reisner@linbit.com&gt;
Signed-off-by: Lars Ellenberg &lt;lars.ellenberg@linbit.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit bbc1c5e8ad6dfebf9d13b8a4ccdf66c92913eac9 upstream.

Since linux kernel 3.13, kthread_run() internally uses
wait_for_completion_killable().  We sometimes may use kthread_run()
while we still have a signal pending, which we used to kick our threads
out of potentially blocking network functions, causing kthread_run() to
mistake that as a new fatal signal and fail.

Fix: flush_signals() before kthread_run().

Signed-off-by: Philipp Reisner &lt;philipp.reisner@linbit.com&gt;
Signed-off-by: Lars Ellenberg &lt;lars.ellenberg@linbit.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: handle parent_overlap on writes correctly</title>
<updated>2014-07-09T18:14:01+00:00</updated>
<author>
<name>Ilya Dryomov</name>
<email>ilya.dryomov@inktank.com</email>
</author>
<published>2014-06-10T09:53:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7029f0641d23ca194e7a596bf8761194b7b70d92'/>
<id>7029f0641d23ca194e7a596bf8761194b7b70d92</id>
<content type='text'>
commit 9638556a276125553549fdfe349c464481ec2f39 upstream.

The following check in rbd_img_obj_request_submit()

    rbd_dev-&gt;parent_overlap &lt;= obj_request-&gt;img_offset

allows the fall through to the non-layered write case even if both
parent_overlap and obj_request-&gt;img_offset belong to the same RADOS
object.  This leads to data corruption, because the area to the left of
parent_overlap ends up unconditionally zero-filled instead of being
populated with parent data.  Suppose we want to write 1M to offset 6M
of image bar, which is a clone of foo@snap; object_size is 4M,
parent_overlap is 5M:

    rbd_data.&lt;id&gt;.0000000000000001
     ---------------------|----------------------|------------
    | should be copyup'ed | should be zeroed out | write ...
     ---------------------|----------------------|------------
   4M                    5M                     6M
                    parent_overlap    obj_request-&gt;img_offset

4..5M should be copyup'ed from foo, yet it is zero-filled, just like
5..6M is.

Given that the only striping mode kernel client currently supports is
chunking (i.e. stripe_unit == object_size, stripe_count == 1), round
parent_overlap up to the next object boundary for the purposes of the
overlap check.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Reviewed-by: Josh Durgin &lt;josh.durgin@inktank.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 9638556a276125553549fdfe349c464481ec2f39 upstream.

The following check in rbd_img_obj_request_submit()

    rbd_dev-&gt;parent_overlap &lt;= obj_request-&gt;img_offset

allows the fall through to the non-layered write case even if both
parent_overlap and obj_request-&gt;img_offset belong to the same RADOS
object.  This leads to data corruption, because the area to the left of
parent_overlap ends up unconditionally zero-filled instead of being
populated with parent data.  Suppose we want to write 1M to offset 6M
of image bar, which is a clone of foo@snap; object_size is 4M,
parent_overlap is 5M:

    rbd_data.&lt;id&gt;.0000000000000001
     ---------------------|----------------------|------------
    | should be copyup'ed | should be zeroed out | write ...
     ---------------------|----------------------|------------
   4M                    5M                     6M
                    parent_overlap    obj_request-&gt;img_offset

4..5M should be copyup'ed from foo, yet it is zero-filled, just like
5..6M is.

Given that the only striping mode kernel client currently supports is
chunking (i.e. stripe_unit == object_size, stripe_count == 1), round
parent_overlap up to the next object boundary for the purposes of the
overlap check.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Reviewed-by: Josh Durgin &lt;josh.durgin@inktank.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: use reference counts for image requests</title>
<updated>2014-07-09T18:14:01+00:00</updated>
<author>
<name>Alex Elder</name>
<email>elder@linaro.org</email>
</author>
<published>2014-04-26T10:21:44+00:00</published>
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commit 0f2d5be792b0466b06797f637cfbb0f64dbb408c upstream.

Each image request contains a reference count, but to date it has
not actually been used.  (I think this was just an oversight.) A
recent report involving rbd failing an assertion shed light on why
and where we need to use these reference counts.

Every OSD request associated with an object request uses
rbd_osd_req_callback() as its callback function.  That function will
call a helper function (dependent on the type of OSD request) that
will set the object request's "done" flag if the object request if
appropriate.  If that "done" flag is set, the object request is
passed to rbd_obj_request_complete().

In rbd_obj_request_complete(), requests are processed in sequential
order.  So if an object request completes before one of its
predecessors in the image request, the completion is deferred.
Otherwise, if it's a completing object's "turn" to be completed, it
is passed to rbd_img_obj_end_request(), which records the result of
the operation, accumulates transferred bytes, and so on.  Next, the
successor to this request is checked and if it is marked "done",
(deferred) completion processing is performed on that request, and
so on.  If the last object request in an image request is completed,
rbd_img_request_complete() is called, which (typically) destroys
the image request.

There is a race here, however.  The instant an object request is
marked "done" it can be provided (by a thread handling completion of
one of its predecessor operations) to rbd_img_obj_end_request(),
which (for the last request) can then lead to the image request
getting torn down.  And this can happen *before* that object has
itself entered rbd_img_obj_end_request().  As a result, once it
*does* enter that function, the image request (and even the object
request itself) may have been freed and become invalid.

All that's necessary to avoid this is to properly count references
to the image requests.  We tear down an image request's object
requests all at once--only when the entire image request has
completed.  So there's no need for an image request to count
references for its object requests.  However, we don't want an
image request to go away until the last of its object requests
has passed through rbd_img_obj_callback().  In other words,
we don't want rbd_img_request_complete() to necessarily
result in the image request being destroyed, because it may
get called before we've finished processing on all of its
object requests.

So the fix is to add a reference to an image request for
each of its object requests.  The reference can be viewed
as representing an object request that has not yet finished
its call to rbd_img_obj_callback().  That is emphasized by
getting the reference right after assigning that as the image
object's callback function.  The corresponding release of that
reference is done at the end of rbd_img_obj_callback(), which
every image object request passes through exactly once.

Signed-off-by: Alex Elder &lt;elder@linaro.org&gt;
Reviewed-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

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<pre>
commit 0f2d5be792b0466b06797f637cfbb0f64dbb408c upstream.

Each image request contains a reference count, but to date it has
not actually been used.  (I think this was just an oversight.) A
recent report involving rbd failing an assertion shed light on why
and where we need to use these reference counts.

Every OSD request associated with an object request uses
rbd_osd_req_callback() as its callback function.  That function will
call a helper function (dependent on the type of OSD request) that
will set the object request's "done" flag if the object request if
appropriate.  If that "done" flag is set, the object request is
passed to rbd_obj_request_complete().

In rbd_obj_request_complete(), requests are processed in sequential
order.  So if an object request completes before one of its
predecessors in the image request, the completion is deferred.
Otherwise, if it's a completing object's "turn" to be completed, it
is passed to rbd_img_obj_end_request(), which records the result of
the operation, accumulates transferred bytes, and so on.  Next, the
successor to this request is checked and if it is marked "done",
(deferred) completion processing is performed on that request, and
so on.  If the last object request in an image request is completed,
rbd_img_request_complete() is called, which (typically) destroys
the image request.

There is a race here, however.  The instant an object request is
marked "done" it can be provided (by a thread handling completion of
one of its predecessor operations) to rbd_img_obj_end_request(),
which (for the last request) can then lead to the image request
getting torn down.  And this can happen *before* that object has
itself entered rbd_img_obj_end_request().  As a result, once it
*does* enter that function, the image request (and even the object
request itself) may have been freed and become invalid.

All that's necessary to avoid this is to properly count references
to the image requests.  We tear down an image request's object
requests all at once--only when the entire image request has
completed.  So there's no need for an image request to count
references for its object requests.  However, we don't want an
image request to go away until the last of its object requests
has passed through rbd_img_obj_callback().  In other words,
we don't want rbd_img_request_complete() to necessarily
result in the image request being destroyed, because it may
get called before we've finished processing on all of its
object requests.

So the fix is to add a reference to an image request for
each of its object requests.  The reference can be viewed
as representing an object request that has not yet finished
its call to rbd_img_obj_callback().  That is emphasized by
getting the reference right after assigning that as the image
object's callback function.  The corresponding release of that
reference is done at the end of rbd_img_obj_callback(), which
every image object request passes through exactly once.

Signed-off-by: Alex Elder &lt;elder@linaro.org&gt;
Reviewed-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
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