<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/fs, branch linux-5.17.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>zonefs: fix handling of explicit_open option on mount</title>
<updated>2022-06-14T16:41:53+00:00</updated>
<author>
<name>Damien Le Moal</name>
<email>damien.lemoal@opensource.wdc.com</email>
</author>
<published>2022-06-02T14:16:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d50efc8d11d2a241d9482ec784881015bfa2da51'/>
<id>d50efc8d11d2a241d9482ec784881015bfa2da51</id>
<content type='text'>
commit a2a513be7139b279f1b5b2cee59c6c4950c34346 upstream.

Ignoring the explicit_open mount option on mount for devices that do not
have a limit on the number of open zones must be done after the mount
options are parsed and set in s_mount_opts. Move the check to ignore
the explicit_open option after the call to zonefs_parse_options() in
zonefs_fill_super().

Fixes: b5c00e975779 ("zonefs: open/close zone on file open/close")
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Damien Le Moal &lt;damien.lemoal@opensource.wdc.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Johannes Thumshirn &lt;johannes.thumshirn@wdc.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 a2a513be7139b279f1b5b2cee59c6c4950c34346 upstream.

Ignoring the explicit_open mount option on mount for devices that do not
have a limit on the number of open zones must be done after the mount
options are parsed and set in s_mount_opts. Move the check to ignore
the explicit_open option after the call to zonefs_parse_options() in
zonefs_fill_super().

Fixes: b5c00e975779 ("zonefs: open/close zone on file open/close")
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Damien Le Moal &lt;damien.lemoal@opensource.wdc.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Johannes Thumshirn &lt;johannes.thumshirn@wdc.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>writeback: Fix inode-&gt;i_io_list not be protected by inode-&gt;i_lock error</title>
<updated>2022-06-14T16:41:47+00:00</updated>
<author>
<name>Jchao Sun</name>
<email>sunjunchao2870@gmail.com</email>
</author>
<published>2022-05-24T15:05:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8e8c954ae2c0e2d002bfc5faad7872c725613549'/>
<id>8e8c954ae2c0e2d002bfc5faad7872c725613549</id>
<content type='text'>
commit 10e14073107dd0b6d97d9516a02845a8e501c2c9 upstream.

Commit b35250c0816c ("writeback: Protect inode-&gt;i_io_list with
inode-&gt;i_lock") made inode-&gt;i_io_list not only protected by
wb-&gt;list_lock but also inode-&gt;i_lock, but inode_io_list_move_locked()
was missed. Add lock there and also update comment describing
things protected by inode-&gt;i_lock. This also fixes a race where
__mark_inode_dirty() could move inode under flush worker's hands
and thus sync(2) could miss writing some inodes.

Fixes: b35250c0816c ("writeback: Protect inode-&gt;i_io_list with inode-&gt;i_lock")
Link: https://lore.kernel.org/r/20220524150540.12552-1-sunjunchao2870@gmail.com
CC: stable@vger.kernel.org
Signed-off-by: Jchao Sun &lt;sunjunchao2870@gmail.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&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 10e14073107dd0b6d97d9516a02845a8e501c2c9 upstream.

Commit b35250c0816c ("writeback: Protect inode-&gt;i_io_list with
inode-&gt;i_lock") made inode-&gt;i_io_list not only protected by
wb-&gt;list_lock but also inode-&gt;i_lock, but inode_io_list_move_locked()
was missed. Add lock there and also update comment describing
things protected by inode-&gt;i_lock. This also fixes a race where
__mark_inode_dirty() could move inode under flush worker's hands
and thus sync(2) could miss writing some inodes.

Fixes: b35250c0816c ("writeback: Protect inode-&gt;i_io_list with inode-&gt;i_lock")
Link: https://lore.kernel.org/r/20220524150540.12552-1-sunjunchao2870@gmail.com
CC: stable@vger.kernel.org
Signed-off-by: Jchao Sun &lt;sunjunchao2870@gmail.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>cifs: populate empty hostnames for extra channels</title>
<updated>2022-06-14T16:41:45+00:00</updated>
<author>
<name>Shyam Prasad N</name>
<email>sprasad@microsoft.com</email>
</author>
<published>2022-06-06T09:52:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=46d520e6a30ef7f5242579fef31f1fd9fa55b95f'/>
<id>46d520e6a30ef7f5242579fef31f1fd9fa55b95f</id>
<content type='text'>
commit 4c14d7043fede258957d7b01da0cad2d9fe3a205 upstream.

Currently, the secondary channels of a multichannel session
also get hostname populated based on the info in primary channel.
However, this will end up with a wrong resolution of hostname to
IP address during reconnect.

This change fixes this by not populating hostname info for all
secondary channels.

Fixes: 5112d80c162f ("cifs: populate server_hostname for extra channels")
Cc: stable@vger.kernel.org
Signed-off-by: Shyam Prasad N &lt;sprasad@microsoft.com&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.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 4c14d7043fede258957d7b01da0cad2d9fe3a205 upstream.

Currently, the secondary channels of a multichannel session
also get hostname populated based on the info in primary channel.
However, this will end up with a wrong resolution of hostname to
IP address during reconnect.

This change fixes this by not populating hostname info for all
secondary channels.

Fixes: 5112d80c162f ("cifs: populate server_hostname for extra channels")
Cc: stable@vger.kernel.org
Signed-off-by: Shyam Prasad N &lt;sprasad@microsoft.com&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>cifs: fix reconnect on smb3 mount types</title>
<updated>2022-06-14T16:41:45+00:00</updated>
<author>
<name>Paulo Alcantara</name>
<email>pc@cjr.nz</email>
</author>
<published>2022-06-05T22:54:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=2194646e41848c4edc80464adbc77b84db3d0f0c'/>
<id>2194646e41848c4edc80464adbc77b84db3d0f0c</id>
<content type='text'>
commit c36ee7dab7749f7be21f7a72392744490b2a9a2b upstream.

cifs.ko defines two file system types: cifs &amp; smb3, and
__cifs_get_super() was not including smb3 file system type when
looking up superblocks, therefore failing to reconnect tcons in
cifs_tree_connect().

Fix this by calling iterate_supers_type() on both file system types.

Link: https://lore.kernel.org/r/CAFrh3J9soC36+BVuwHB=g9z_KB5Og2+p2_W+BBoBOZveErz14w@mail.gmail.com
Cc: stable@vger.kernel.org
Tested-by: Satadru Pramanik &lt;satadru@gmail.com&gt;
Reported-by: Satadru Pramanik &lt;satadru@gmail.com&gt;
Signed-off-by: Paulo Alcantara (SUSE) &lt;pc@cjr.nz&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.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 c36ee7dab7749f7be21f7a72392744490b2a9a2b upstream.

cifs.ko defines two file system types: cifs &amp; smb3, and
__cifs_get_super() was not including smb3 file system type when
looking up superblocks, therefore failing to reconnect tcons in
cifs_tree_connect().

Fix this by calling iterate_supers_type() on both file system types.

Link: https://lore.kernel.org/r/CAFrh3J9soC36+BVuwHB=g9z_KB5Og2+p2_W+BBoBOZveErz14w@mail.gmail.com
Cc: stable@vger.kernel.org
Tested-by: Satadru Pramanik &lt;satadru@gmail.com&gt;
Reported-by: Satadru Pramanik &lt;satadru@gmail.com&gt;
Signed-off-by: Paulo Alcantara (SUSE) &lt;pc@cjr.nz&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>cifs: return errors during session setup during reconnects</title>
<updated>2022-06-14T16:41:44+00:00</updated>
<author>
<name>Shyam Prasad N</name>
<email>sprasad@microsoft.com</email>
</author>
<published>2022-05-31T12:31:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5a61ba459e128b2afdce21612b8cda8a80616954'/>
<id>5a61ba459e128b2afdce21612b8cda8a80616954</id>
<content type='text'>
commit 8ea21823aa584b55ba4b861307093b78054b0c1b upstream.

During reconnects, we check the return value from
cifs_negotiate_protocol, and have handlers for both success
and failures. But if that passes, and cifs_setup_session
returns any errors other than -EACCES, we do not handle
that. This fix adds a handler for that, so that we don't
go ahead and try a tree_connect on a failed session.

Signed-off-by: Shyam Prasad N &lt;sprasad@microsoft.com&gt;
Reviewed-by: Enzo Matsumiya &lt;ematsumiya@suse.de&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Steve French &lt;stfrench@microsoft.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 8ea21823aa584b55ba4b861307093b78054b0c1b upstream.

During reconnects, we check the return value from
cifs_negotiate_protocol, and have handlers for both success
and failures. But if that passes, and cifs_setup_session
returns any errors other than -EACCES, we do not handle
that. This fix adds a handler for that, so that we don't
go ahead and try a tree_connect on a failed session.

Signed-off-by: Shyam Prasad N &lt;sprasad@microsoft.com&gt;
Reviewed-by: Enzo Matsumiya &lt;ematsumiya@suse.de&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>cifs: version operations for smb20 unneeded when legacy support disabled</title>
<updated>2022-06-14T16:41:41+00:00</updated>
<author>
<name>Steve French</name>
<email>stfrench@microsoft.com</email>
</author>
<published>2022-06-02T03:08:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=278cd0d714d5fdbfc69364b3ec1c27d2d5e2d13f'/>
<id>278cd0d714d5fdbfc69364b3ec1c27d2d5e2d13f</id>
<content type='text'>
[ Upstream commit 7ef93ffccd55fb0ba000ed16ef6a81cd7dee07b5 ]

We should not be including unused smb20 specific code when legacy
support is disabled (CONFIG_CIFS_ALLOW_INSECURE_LEGACY turned
off).  For example smb2_operations and smb2_values aren't used
in that case.  Over time we can move more and more SMB1/CIFS and SMB2.0
code into the insecure legacy ifdefs

Reviewed-by: Ronnie Sahlberg &lt;lsahlber@redhat.com&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 7ef93ffccd55fb0ba000ed16ef6a81cd7dee07b5 ]

We should not be including unused smb20 specific code when legacy
support is disabled (CONFIG_CIFS_ALLOW_INSECURE_LEGACY turned
off).  For example smb2_operations and smb2_values aren't used
in that case.  Over time we can move more and more SMB1/CIFS and SMB2.0
code into the insecure legacy ifdefs

Reviewed-by: Ronnie Sahlberg &lt;lsahlber@redhat.com&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ceph: flush the mdlog for filesystem sync</title>
<updated>2022-06-14T16:41:37+00:00</updated>
<author>
<name>Xiubo Li</name>
<email>xiubli@redhat.com</email>
</author>
<published>2022-04-19T00:58:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=3e25051763603c3d70f23472bb1ee51d7d26b7be'/>
<id>3e25051763603c3d70f23472bb1ee51d7d26b7be</id>
<content type='text'>
[ Upstream commit 1b2ba3c5616e17ff951359e25c658a1c3f146f1e ]

Before waiting for a request's safe reply, we will send the mdlog flush
request to the relevant MDS. And this will also flush the mdlog for all
the other unsafe requests in the same session, so we can record the last
session and no need to flush mdlog again in the next loop. But there
still have cases that it may send the mdlog flush requst twice or more,
but that should be not often.

Rename wait_unsafe_requests() to
flush_mdlog_and_wait_mdsc_unsafe_requests() to make it more
descriptive.

[xiubli: fold in MDS request refcount leak fix from Jeff]

URL: https://tracker.ceph.com/issues/55284
URL: https://tracker.ceph.com/issues/55411
Signed-off-by: Xiubo Li &lt;xiubli@redhat.com&gt;
Reviewed-by: Jeff Layton &lt;jlayton@kernel.org&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 1b2ba3c5616e17ff951359e25c658a1c3f146f1e ]

Before waiting for a request's safe reply, we will send the mdlog flush
request to the relevant MDS. And this will also flush the mdlog for all
the other unsafe requests in the same session, so we can record the last
session and no need to flush mdlog again in the next loop. But there
still have cases that it may send the mdlog flush requst twice or more,
but that should be not often.

Rename wait_unsafe_requests() to
flush_mdlog_and_wait_mdsc_unsafe_requests() to make it more
descriptive.

[xiubli: fold in MDS request refcount leak fix from Jeff]

URL: https://tracker.ceph.com/issues/55284
URL: https://tracker.ceph.com/issues/55411
Signed-off-by: Xiubo Li &lt;xiubli@redhat.com&gt;
Reviewed-by: Jeff Layton &lt;jlayton@kernel.org&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ceph: allow ceph.dir.rctime xattr to be updatable</title>
<updated>2022-06-14T16:41:37+00:00</updated>
<author>
<name>Venky Shankar</name>
<email>vshankar@redhat.com</email>
</author>
<published>2022-03-10T14:34:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7e195336c1080bf951070079a7ea9f93020d6465'/>
<id>7e195336c1080bf951070079a7ea9f93020d6465</id>
<content type='text'>
[ Upstream commit d7a2dc523085f8b8c60548ceedc696934aefeb0e ]

`rctime' has been a pain point in cephfs due to its buggy
nature - inconsistent values reported and those sorts.
Fixing rctime is non-trivial needing an overall redesign
of the entire nested statistics infrastructure.

As a workaround, PR

     http://github.com/ceph/ceph/pull/37938

allows this extended attribute to be manually set. This allows
users to "fixup" inconsistent rctime values. While this sounds
messy, its probably the wisest approach allowing users/scripts
to workaround buggy rctime values.

The above PR enables Ceph MDS to allow manually setting
rctime extended attribute with the corresponding user-land
changes. We may as well allow the same to be done via kclient
for parity.

Signed-off-by: Venky Shankar &lt;vshankar@redhat.com&gt;
Reviewed-by: Xiubo Li &lt;xiubli@redhat.com&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit d7a2dc523085f8b8c60548ceedc696934aefeb0e ]

`rctime' has been a pain point in cephfs due to its buggy
nature - inconsistent values reported and those sorts.
Fixing rctime is non-trivial needing an overall redesign
of the entire nested statistics infrastructure.

As a workaround, PR

     http://github.com/ceph/ceph/pull/37938

allows this extended attribute to be manually set. This allows
users to "fixup" inconsistent rctime values. While this sounds
messy, its probably the wisest approach allowing users/scripts
to workaround buggy rctime values.

The above PR enables Ceph MDS to allow manually setting
rctime extended attribute with the corresponding user-land
changes. We may as well allow the same to be done via kclient
for parity.

Signed-off-by: Venky Shankar &lt;vshankar@redhat.com&gt;
Reviewed-by: Xiubo Li &lt;xiubli@redhat.com&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ksmbd: smbd: fix connection dropped issue</title>
<updated>2022-06-14T16:41:36+00:00</updated>
<author>
<name>Hyunchul Lee</name>
<email>hyc.lee@gmail.com</email>
</author>
<published>2022-05-17T21:46:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=0945b0d34aac4571c96276641657d85eb9af4ec8'/>
<id>0945b0d34aac4571c96276641657d85eb9af4ec8</id>
<content type='text'>
[ Upstream commit 5366afc4065075a4456941fbd51c33604d631ee5 ]

When there are bursty connection requests,
RDMA connection event handler is deferred and
Negotiation requests are received even if
connection status is NEW.

To handle it, set the status to CONNECTED
if Negotiation requests are received.

Reported-by: Yufan Chen &lt;wiz.chen@gmail.com&gt;
Signed-off-by: Hyunchul Lee &lt;hyc.lee@gmail.com&gt;
Tested-by: Yufan Chen &lt;wiz.chen@gmail.com&gt;
Acked-by: Namjae Jeon &lt;linkinjeon@kernel.org&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 5366afc4065075a4456941fbd51c33604d631ee5 ]

When there are bursty connection requests,
RDMA connection event handler is deferred and
Negotiation requests are received even if
connection status is NEW.

To handle it, set the status to CONNECTED
if Negotiation requests are received.

Reported-by: Yufan Chen &lt;wiz.chen@gmail.com&gt;
Signed-off-by: Hyunchul Lee &lt;hyc.lee@gmail.com&gt;
Tested-by: Yufan Chen &lt;wiz.chen@gmail.com&gt;
Acked-by: Namjae Jeon &lt;linkinjeon@kernel.org&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>kernfs: Separate kernfs_pr_cont_buf and rename_lock.</title>
<updated>2022-06-14T16:41:36+00:00</updated>
<author>
<name>Hao Luo</name>
<email>haoluo@google.com</email>
</author>
<published>2022-05-16T19:09:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=894a152eca743c17cd4ee72b67974d66cca280ba'/>
<id>894a152eca743c17cd4ee72b67974d66cca280ba</id>
<content type='text'>
[ Upstream commit 1a702dc88e150487c9c173a249b3d236498b9183 ]

Previously the protection of kernfs_pr_cont_buf was piggy backed by
rename_lock, which means that pr_cont() needs to be protected under
rename_lock. This can cause potential circular lock dependencies.

If there is an OOM, we have the following call hierarchy:

 -&gt; cpuset_print_current_mems_allowed()
   -&gt; pr_cont_cgroup_name()
     -&gt; pr_cont_kernfs_name()

pr_cont_kernfs_name() will grab rename_lock and call printk. So we have
the following lock dependencies:

 kernfs_rename_lock -&gt; console_sem

Sometimes, printk does a wakeup before releasing console_sem, which has
the dependence chain:

 console_sem -&gt; p-&gt;pi_lock -&gt; rq-&gt;lock

Now, imagine one wants to read cgroup_name under rq-&gt;lock, for example,
printing cgroup_name in a tracepoint in the scheduler code. They will
be holding rq-&gt;lock and take rename_lock:

 rq-&gt;lock -&gt; kernfs_rename_lock

Now they will deadlock.

A prevention to this circular lock dependency is to separate the
protection of pr_cont_buf from rename_lock. In principle, rename_lock
is to protect the integrity of cgroup name when copying to buf. Once
pr_cont_buf has got its content, rename_lock can be dropped. So it's
safe to drop rename_lock after kernfs_name_locked (and
kernfs_path_from_node_locked) and rely on a dedicated pr_cont_lock
to protect pr_cont_buf.

Acked-by: Tejun Heo &lt;tj@kernel.org&gt;
Signed-off-by: Hao Luo &lt;haoluo@google.com&gt;
Link: https://lore.kernel.org/r/20220516190951.3144144-1-haoluo@google.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
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[ Upstream commit 1a702dc88e150487c9c173a249b3d236498b9183 ]

Previously the protection of kernfs_pr_cont_buf was piggy backed by
rename_lock, which means that pr_cont() needs to be protected under
rename_lock. This can cause potential circular lock dependencies.

If there is an OOM, we have the following call hierarchy:

 -&gt; cpuset_print_current_mems_allowed()
   -&gt; pr_cont_cgroup_name()
     -&gt; pr_cont_kernfs_name()

pr_cont_kernfs_name() will grab rename_lock and call printk. So we have
the following lock dependencies:

 kernfs_rename_lock -&gt; console_sem

Sometimes, printk does a wakeup before releasing console_sem, which has
the dependence chain:

 console_sem -&gt; p-&gt;pi_lock -&gt; rq-&gt;lock

Now, imagine one wants to read cgroup_name under rq-&gt;lock, for example,
printing cgroup_name in a tracepoint in the scheduler code. They will
be holding rq-&gt;lock and take rename_lock:

 rq-&gt;lock -&gt; kernfs_rename_lock

Now they will deadlock.

A prevention to this circular lock dependency is to separate the
protection of pr_cont_buf from rename_lock. In principle, rename_lock
is to protect the integrity of cgroup name when copying to buf. Once
pr_cont_buf has got its content, rename_lock can be dropped. So it's
safe to drop rename_lock after kernfs_name_locked (and
kernfs_path_from_node_locked) and rely on a dedicated pr_cont_lock
to protect pr_cont_buf.

Acked-by: Tejun Heo &lt;tj@kernel.org&gt;
Signed-off-by: Hao Luo &lt;haoluo@google.com&gt;
Link: https://lore.kernel.org/r/20220516190951.3144144-1-haoluo@google.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
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