<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/fs, branch v3.2.38</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>NFSv4.1: Handle NFS4ERR_DELAY when resetting the NFSv4.1 session</title>
<updated>2013-02-06T04:33:51+00:00</updated>
<author>
<name>Trond Myklebust</name>
<email>Trond.Myklebust@netapp.com</email>
</author>
<published>2013-01-30T18:04:10+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=78e3ae2d57c0df313b079a07f6ffc16e4041e56c'/>
<id>78e3ae2d57c0df313b079a07f6ffc16e4041e56c</id>
<content type='text'>
commit c489ee290bdbbace6bb63ebe6ebd4dd605819495 upstream.

NFS4ERR_DELAY is a legal reply when we call DESTROY_SESSION. It
usually means that the server is busy handling an unfinished RPC
request. Just sleep for a second and then retry.
We also need to be able to handle the NFS4ERR_BACK_CHAN_BUSY return
value. If the NFS server has outstanding callbacks, we just want to
similarly sleep &amp; retry.

Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit c489ee290bdbbace6bb63ebe6ebd4dd605819495 upstream.

NFS4ERR_DELAY is a legal reply when we call DESTROY_SESSION. It
usually means that the server is busy handling an unfinished RPC
request. Just sleep for a second and then retry.
We also need to be able to handle the NFS4ERR_BACK_CHAN_BUSY return
value. If the NFS server has outstanding callbacks, we just want to
similarly sleep &amp; retry.

Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>NFS: Don't silently fail setattr() requests on mountpoints</title>
<updated>2013-02-06T04:33:51+00:00</updated>
<author>
<name>Trond Myklebust</name>
<email>Trond.Myklebust@netapp.com</email>
</author>
<published>2013-01-22T05:17:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8e61814f416e0069dbcedbe15509c0a5b5af9da6'/>
<id>8e61814f416e0069dbcedbe15509c0a5b5af9da6</id>
<content type='text'>
commit ab225417825963b6dc66be7ea80f94ac1378dfdf upstream.

Ensure that any setattr and getattr requests for junctions and/or
mountpoints are sent to the server. Ever since commit
0ec26fd0698 (vfs: automount should ignore LOOKUP_FOLLOW), we have
silently dropped any setattr requests to a server-side mountpoint.
For referrals, we have silently dropped both getattr and setattr
requests.

This patch restores the original behaviour for setattr on mountpoints,
and tries to do the same for referrals, provided that we have a
filehandle...

Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit ab225417825963b6dc66be7ea80f94ac1378dfdf upstream.

Ensure that any setattr and getattr requests for junctions and/or
mountpoints are sent to the server. Ever since commit
0ec26fd0698 (vfs: automount should ignore LOOKUP_FOLLOW), we have
silently dropped any setattr requests to a server-side mountpoint.
For referrals, we have silently dropped both getattr and setattr
requests.

This patch restores the original behaviour for setattr on mountpoints,
and tries to do the same for referrals, provided that we have a
filehandle...

Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>xfs: Fix possible use-after-free with AIO</title>
<updated>2013-02-06T04:33:49+00:00</updated>
<author>
<name>Jan Kara</name>
<email>jack@suse.cz</email>
</author>
<published>2013-01-23T12:56:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e807626e32eb159914cee54473d17082a1920039'/>
<id>e807626e32eb159914cee54473d17082a1920039</id>
<content type='text'>
commit 4b05d09c18d9aa62d2e7fb4b057f54e5a38963f5 upstream.

Running AIO is pinning inode in memory using file reference. Once AIO
is completed using aio_complete(), file reference is put and inode can
be freed from memory. So we have to be sure that calling aio_complete()
is the last thing we do with the inode.

CC: xfs@oss.sgi.com
CC: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Reviewed-by: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 4b05d09c18d9aa62d2e7fb4b057f54e5a38963f5 upstream.

Running AIO is pinning inode in memory using file reference. Once AIO
is completed using aio_complete(), file reference is put and inode can
be freed from memory. So we have to be sure that calling aio_complete()
is the last thing we do with the inode.

CC: xfs@oss.sgi.com
CC: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Reviewed-by: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Ben Myers &lt;bpm@sgi.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fs/cifs/cifs_dfs_ref.c: fix potential memory leakage</title>
<updated>2013-02-06T04:33:42+00:00</updated>
<author>
<name>Cong Ding</name>
<email>dinggnu@gmail.com</email>
</author>
<published>2013-01-23T00:20:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d62f0c40e67bb539c1e2101f7577a97889bb43cd'/>
<id>d62f0c40e67bb539c1e2101f7577a97889bb43cd</id>
<content type='text'>
commit 10b8c7dff5d3633b69e77f57d404dab54ead3787 upstream.

When it goes to error through line 144, the memory allocated to *devname is
not freed, and the caller doesn't free it either in line 250. So we free the
memroy of *devname in function cifs_compose_mount_options() when it goes to
error.

Signed-off-by: Cong Ding &lt;dinggnu@gmail.com&gt;
Reviewed-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Steve French &lt;smfrench@gmail.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 10b8c7dff5d3633b69e77f57d404dab54ead3787 upstream.

When it goes to error through line 144, the memory allocated to *devname is
not freed, and the caller doesn't free it either in line 250. So we free the
memroy of *devname in function cifs_compose_mount_options() when it goes to
error.

Signed-off-by: Cong Ding &lt;dinggnu@gmail.com&gt;
Reviewed-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Steve French &lt;smfrench@gmail.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>epoll: prevent missed events on EPOLL_CTL_MOD</title>
<updated>2013-01-16T01:13:22+00:00</updated>
<author>
<name>Eric Wong</name>
<email>normalperson@yhbt.net</email>
</author>
<published>2013-01-01T21:20:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=416db02bea8fa54c5946bfce2df5001d6a07f560'/>
<id>416db02bea8fa54c5946bfce2df5001d6a07f560</id>
<content type='text'>
commit 128dd1759d96ad36c379240f8b9463e8acfd37a1 upstream.

EPOLL_CTL_MOD sets the interest mask before calling f_op-&gt;poll() to
ensure events are not missed.  Since the modifications to the interest
mask are not protected by the same lock as ep_poll_callback, we need to
ensure the change is visible to other CPUs calling ep_poll_callback.

We also need to ensure f_op-&gt;poll() has an up-to-date view of past
events which occured before we modified the interest mask.  So this
barrier also pairs with the barrier in wq_has_sleeper().

This should guarantee either ep_poll_callback or f_op-&gt;poll() (or both)
will notice the readiness of a recently-ready/modified item.

This issue was encountered by Andreas Voellmy and Junchang(Jason) Wang in:
http://thread.gmane.org/gmane.linux.kernel/1408782/

Signed-off-by: Eric Wong &lt;normalperson@yhbt.net&gt;
Cc: Hans Verkuil &lt;hans.verkuil@cisco.com&gt;
Cc: Jiri Olsa &lt;jolsa@redhat.com&gt;
Cc: Jonathan Corbet &lt;corbet@lwn.net&gt;
Cc: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Davide Libenzi &lt;davidel@xmailserver.org&gt;
Cc: Hans de Goede &lt;hdegoede@redhat.com&gt;
Cc: Mauro Carvalho Chehab &lt;mchehab@infradead.org&gt;
Cc: David Miller &lt;davem@davemloft.net&gt;
Cc: Eric Dumazet &lt;eric.dumazet@gmail.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Andreas Voellmy &lt;andreas.voellmy@yale.edu&gt;
Tested-by: "Junchang(Jason) Wang" &lt;junchang.wang@yale.edu&gt;
Cc: netdev@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 128dd1759d96ad36c379240f8b9463e8acfd37a1 upstream.

EPOLL_CTL_MOD sets the interest mask before calling f_op-&gt;poll() to
ensure events are not missed.  Since the modifications to the interest
mask are not protected by the same lock as ep_poll_callback, we need to
ensure the change is visible to other CPUs calling ep_poll_callback.

We also need to ensure f_op-&gt;poll() has an up-to-date view of past
events which occured before we modified the interest mask.  So this
barrier also pairs with the barrier in wq_has_sleeper().

This should guarantee either ep_poll_callback or f_op-&gt;poll() (or both)
will notice the readiness of a recently-ready/modified item.

This issue was encountered by Andreas Voellmy and Junchang(Jason) Wang in:
http://thread.gmane.org/gmane.linux.kernel/1408782/

Signed-off-by: Eric Wong &lt;normalperson@yhbt.net&gt;
Cc: Hans Verkuil &lt;hans.verkuil@cisco.com&gt;
Cc: Jiri Olsa &lt;jolsa@redhat.com&gt;
Cc: Jonathan Corbet &lt;corbet@lwn.net&gt;
Cc: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Davide Libenzi &lt;davidel@xmailserver.org&gt;
Cc: Hans de Goede &lt;hdegoede@redhat.com&gt;
Cc: Mauro Carvalho Chehab &lt;mchehab@infradead.org&gt;
Cc: David Miller &lt;davem@davemloft.net&gt;
Cc: Eric Dumazet &lt;eric.dumazet@gmail.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Andreas Voellmy &lt;andreas.voellmy@yale.edu&gt;
Tested-by: "Junchang(Jason) Wang" &lt;junchang.wang@yale.edu&gt;
Cc: netdev@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>udf: don't increment lenExtents while writing to a hole</title>
<updated>2013-01-16T01:13:21+00:00</updated>
<author>
<name>Namjae Jeon</name>
<email>namjae.jeon@samsung.com</email>
</author>
<published>2012-10-09T15:09:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=89c712397ea01a6c6e93fca0f9c4e21000ec358b'/>
<id>89c712397ea01a6c6e93fca0f9c4e21000ec358b</id>
<content type='text'>
commit fb719c59bdb4fca86ee1fd1f42ab3735ca12b6b2 upstream.

Incrementing lenExtents even while writing to a hole is bad
for performance as calls to udf_discard_prealloc and
udf_truncate_tail_extent would not return from start if
isize != lenExtents

Signed-off-by: Namjae Jeon &lt;namjae.jeon@samsung.com&gt;
Signed-off-by: Ashish Sangwan &lt;a.sangwan@samsung.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit fb719c59bdb4fca86ee1fd1f42ab3735ca12b6b2 upstream.

Incrementing lenExtents even while writing to a hole is bad
for performance as calls to udf_discard_prealloc and
udf_truncate_tail_extent would not return from start if
isize != lenExtents

Signed-off-by: Namjae Jeon &lt;namjae.jeon@samsung.com&gt;
Signed-off-by: Ashish Sangwan &lt;a.sangwan@samsung.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>nfs: fix null checking in nfs_get_option_str()</title>
<updated>2013-01-16T01:13:19+00:00</updated>
<author>
<name>Xi Wang</name>
<email>xi.wang@gmail.com</email>
</author>
<published>2013-01-04T08:22:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=66ebe467a6dbbd0b3917ef6ad1bd4930f9b8185d'/>
<id>66ebe467a6dbbd0b3917ef6ad1bd4930f9b8185d</id>
<content type='text'>
commit e25fbe380c4e3c09afa98bcdcd9d3921443adab8 upstream.

The following null pointer check is broken.

	*option = match_strdup(args);
	return !option;

The pointer `option' must be non-null, and thus `!option' is always false.
Use `!*option' instead.

The bug was introduced in commit c5cb09b6f8 ("Cleanup: Factor out some
cut-and-paste code.").

Signed-off-by: Xi Wang &lt;xi.wang@gmail.com&gt;
Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit e25fbe380c4e3c09afa98bcdcd9d3921443adab8 upstream.

The following null pointer check is broken.

	*option = match_strdup(args);
	return !option;

The pointer `option' must be non-null, and thus `!option' is always false.
Use `!*option' instead.

The bug was introduced in commit c5cb09b6f8 ("Cleanup: Factor out some
cut-and-paste code.").

Signed-off-by: Xi Wang &lt;xi.wang@gmail.com&gt;
Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>cifs: adjust sequence number downward after signing NT_CANCEL request</title>
<updated>2013-01-16T01:13:13+00:00</updated>
<author>
<name>Jeff Layton</name>
<email>jlayton@redhat.com</email>
</author>
<published>2012-12-27T13:05:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f6f82cba2ccbf6a77278c7c3f2e4daf23063944a'/>
<id>f6f82cba2ccbf6a77278c7c3f2e4daf23063944a</id>
<content type='text'>
commit 31efee60f489c759c341454d755a9fd13de8c03d upstream.

When a call goes out, the signing code adjusts the sequence number
upward by two to account for the request and the response. An NT_CANCEL
however doesn't get a response of its own, it just hurries the server
along to get it to respond to the original request more quickly.
Therefore, we must adjust the sequence number back down by one after
signing a NT_CANCEL request.

Reported-by: Tim Perry &lt;tdparmor-sambabugs@yahoo.com&gt;
Signed-off-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Steve French &lt;smfrench@gmail.com&gt;
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 31efee60f489c759c341454d755a9fd13de8c03d upstream.

When a call goes out, the signing code adjusts the sequence number
upward by two to account for the request and the response. An NT_CANCEL
however doesn't get a response of its own, it just hurries the server
along to get it to respond to the original request more quickly.
Therefore, we must adjust the sequence number back down by one after
signing a NT_CANCEL request.

Reported-by: Tim Perry &lt;tdparmor-sambabugs@yahoo.com&gt;
Signed-off-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Steve French &lt;smfrench@gmail.com&gt;
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: do not try to write superblock on ro remount w/o journal</title>
<updated>2013-01-16T01:13:12+00:00</updated>
<author>
<name>Michael Tokarev</name>
<email>mjt@tls.msk.ru</email>
</author>
<published>2012-12-25T19:08:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ad74aa67b8cf06b159cf72b08efe42533db49685'/>
<id>ad74aa67b8cf06b159cf72b08efe42533db49685</id>
<content type='text'>
commit d096ad0f79a782935d2e06ae8fb235e8c5397775 upstream.

When a journal-less ext4 filesystem is mounted on a read-only block
device (blockdev --setro will do), each remount (for other, unrelated,
flags, like suid=&gt;nosuid etc) results in a series of scary messages
from kernel telling about I/O errors on the device.

This is becauese of the following code ext4_remount():

       if (sbi-&gt;s_journal == NULL)
                ext4_commit_super(sb, 1);

at the end of remount procedure, which forces writing (flushing) of
a superblock regardless whenever it is dirty or not, if the filesystem
is readonly or not, and whenever the device itself is readonly or not.

We only need call ext4_commit_super when the file system had been
previously mounted read/write.

Thanks to Eric Sandeen for help in diagnosing this issue.

Signed-off-By: Michael Tokarev &lt;mjt@tls.msk.ru&gt;
Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit d096ad0f79a782935d2e06ae8fb235e8c5397775 upstream.

When a journal-less ext4 filesystem is mounted on a read-only block
device (blockdev --setro will do), each remount (for other, unrelated,
flags, like suid=&gt;nosuid etc) results in a series of scary messages
from kernel telling about I/O errors on the device.

This is becauese of the following code ext4_remount():

       if (sbi-&gt;s_journal == NULL)
                ext4_commit_super(sb, 1);

at the end of remount procedure, which forces writing (flushing) of
a superblock regardless whenever it is dirty or not, if the filesystem
is readonly or not, and whenever the device itself is readonly or not.

We only need call ext4_commit_super when the file system had been
previously mounted read/write.

Thanks to Eric Sandeen for help in diagnosing this issue.

Signed-off-By: Michael Tokarev &lt;mjt@tls.msk.ru&gt;
Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>jbd2: fix assertion failure in jbd2_journal_flush()</title>
<updated>2013-01-16T01:13:11+00:00</updated>
<author>
<name>Jan Kara</name>
<email>jack@suse.cz</email>
</author>
<published>2012-12-21T05:15:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=7a55283222cdd70c1cd7a33df0db1e0c96462ac9'/>
<id>7a55283222cdd70c1cd7a33df0db1e0c96462ac9</id>
<content type='text'>
commit d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a upstream.

The following race is possible between start_this_handle() and someone
calling jbd2_journal_flush().

Process A                              Process B
start_this_handle().
  if (journal-&gt;j_barrier_count) # false
  if (!journal-&gt;j_running_transaction) { #true
    read_unlock(&amp;journal-&gt;j_state_lock);
                                       jbd2_journal_lock_updates()
                                       jbd2_journal_flush()
                                         write_lock(&amp;journal-&gt;j_state_lock);
                                         if (journal-&gt;j_running_transaction) {
                                           # false
                                         ... wait for committing trans ...
                                         write_unlock(&amp;journal-&gt;j_state_lock);
    ...
    write_lock(&amp;journal-&gt;j_state_lock);
    if (!journal-&gt;j_running_transaction) { # true
      jbd2_get_transaction(journal, new_transaction);
    write_unlock(&amp;journal-&gt;j_state_lock);
    goto repeat; # eventually blocks on j_barrier_count &gt; 0
                                         ...
                                         J_ASSERT(!journal-&gt;j_running_transaction);
                                           # fails

We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
in exclusive mode.

Reported-by: yjwsignal@empal.com
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
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<pre>
commit d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a upstream.

The following race is possible between start_this_handle() and someone
calling jbd2_journal_flush().

Process A                              Process B
start_this_handle().
  if (journal-&gt;j_barrier_count) # false
  if (!journal-&gt;j_running_transaction) { #true
    read_unlock(&amp;journal-&gt;j_state_lock);
                                       jbd2_journal_lock_updates()
                                       jbd2_journal_flush()
                                         write_lock(&amp;journal-&gt;j_state_lock);
                                         if (journal-&gt;j_running_transaction) {
                                           # false
                                         ... wait for committing trans ...
                                         write_unlock(&amp;journal-&gt;j_state_lock);
    ...
    write_lock(&amp;journal-&gt;j_state_lock);
    if (!journal-&gt;j_running_transaction) { # true
      jbd2_get_transaction(journal, new_transaction);
    write_unlock(&amp;journal-&gt;j_state_lock);
    goto repeat; # eventually blocks on j_barrier_count &gt; 0
                                         ...
                                         J_ASSERT(!journal-&gt;j_running_transaction);
                                           # fails

We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
in exclusive mode.

Reported-by: yjwsignal@empal.com
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
</pre>
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