<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/fs/ext2, branch v4.4.158</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>do d_instantiate/unlock_new_inode combinations safely</title>
<updated>2018-05-30T05:48:52+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2018-05-04T12:23:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=03bb7588942a38623f108b3302c2d1aebb525696'/>
<id>03bb7588942a38623f108b3302c2d1aebb525696</id>
<content type='text'>
commit 1e2e547a93a00ebc21582c06ca3c6cfea2a309ee upstream.

For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
	lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
-&gt;i_mutex.  Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.

	Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode().  All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.

Cc: stable@kernel.org	# 2.6.29 and later
Tested-by: Mike Marshall &lt;hubcap@omnibond.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&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 1e2e547a93a00ebc21582c06ca3c6cfea2a309ee upstream.

For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
	lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
-&gt;i_mutex.  Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.

	Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode().  All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.

Cc: stable@kernel.org	# 2.6.29 and later
Tested-by: Mike Marshall &lt;hubcap@omnibond.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>ext2: fix a block leak</title>
<updated>2018-05-26T06:48:58+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2018-05-17T21:18:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3cd868dc9b68709d7274120f7ef1c6063948910d'/>
<id>3cd868dc9b68709d7274120f7ef1c6063948910d</id>
<content type='text'>
commit 5aa1437d2d9a068c0334bd7c9dafa8ec4f97f13b upstream.

open file, unlink it, then use ioctl(2) to make it immutable or
append only.  Now close it and watch the blocks *not* freed...

Immutable/append-only checks belong in -&gt;setattr().
Note: the bug is old and backport to anything prior to 737f2e93b972
("ext2: convert to use the new truncate convention") will need
these checks lifted into ext2_setattr().

Cc: stable@kernel.org
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&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 5aa1437d2d9a068c0334bd7c9dafa8ec4f97f13b upstream.

open file, unlink it, then use ioctl(2) to make it immutable or
append only.  Now close it and watch the blocks *not* freed...

Immutable/append-only checks belong in -&gt;setattr().
Note: the bug is old and backport to anything prior to 737f2e93b972
("ext2: convert to use the new truncate convention") will need
these checks lifted into ext2_setattr().

Cc: stable@kernel.org
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>ext2: Don't clear SGID when inheriting ACLs</title>
<updated>2018-01-31T11:06:11+00:00</updated>
<author>
<name>Jan Kara</name>
<email>jack@suse.cz</email>
</author>
<published>2017-06-21T12:34:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8e8224de0e1848a5905ebda018969e2ce72258ca'/>
<id>8e8224de0e1848a5905ebda018969e2ce72258ca</id>
<content type='text'>
commit a992f2d38e4ce17b8c7d1f7f67b2de0eebdea069 upstream.

When new directory 'DIR1' is created in a directory 'DIR0' with SGID bit
set, DIR1 is expected to have SGID bit set (and owning group equal to
the owning group of 'DIR0'). However when 'DIR0' also has some default
ACLs that 'DIR1' inherits, setting these ACLs will result in SGID bit on
'DIR1' to get cleared if user is not member of the owning group.

Fix the problem by creating __ext2_set_acl() function that does not call
posix_acl_update_mode() and use it when inheriting ACLs. That prevents
SGID bit clearing and the mode has been properly set by
posix_acl_create() anyway.

Fixes: 073931017b49d9458aa351605b43a7e34598caef
CC: stable@vger.kernel.org
CC: linux-ext4@vger.kernel.org
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 a992f2d38e4ce17b8c7d1f7f67b2de0eebdea069 upstream.

When new directory 'DIR1' is created in a directory 'DIR0' with SGID bit
set, DIR1 is expected to have SGID bit set (and owning group equal to
the owning group of 'DIR0'). However when 'DIR0' also has some default
ACLs that 'DIR1' inherits, setting these ACLs will result in SGID bit on
'DIR1' to get cleared if user is not member of the owning group.

Fix the problem by creating __ext2_set_acl() function that does not call
posix_acl_update_mode() and use it when inheriting ACLs. That prevents
SGID bit clearing and the mode has been properly set by
posix_acl_create() anyway.

Fixes: 073931017b49d9458aa351605b43a7e34598caef
CC: stable@vger.kernel.org
CC: linux-ext4@vger.kernel.org
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>posix_acl: Clear SGID bit when setting file permissions</title>
<updated>2016-10-31T10:13:58+00:00</updated>
<author>
<name>Jan Kara</name>
<email>jack@suse.cz</email>
</author>
<published>2016-09-19T15:39:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=57c9cfdb61ea270936fab76da99a742c6ef0b86f'/>
<id>57c9cfdb61ea270936fab76da99a742c6ef0b86f</id>
<content type='text'>
commit 073931017b49d9458aa351605b43a7e34598caef upstream.

When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2).  Fix that.

References: CVE-2016-7097
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Andreas Gruenbacher &lt;agruenba@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 073931017b49d9458aa351605b43a7e34598caef upstream.

When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2).  Fix that.

References: CVE-2016-7097
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Jeff Layton &lt;jlayton@redhat.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.cz&gt;
Signed-off-by: Andreas Gruenbacher &lt;agruenba@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>ext2, ext4: warn when mounting with dax enabled</title>
<updated>2015-11-16T17:43:54+00:00</updated>
<author>
<name>Dan Williams</name>
<email>dan.j.williams@intel.com</email>
</author>
<published>2015-09-29T19:48:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ef83b6e8f40bb24b92ad73b5889732346e54a793'/>
<id>ef83b6e8f40bb24b92ad73b5889732346e54a793</id>
<content type='text'>
Similar to XFS warn when mounting DAX while it is still considered under
development.  Also, aspects of the DAX implementation, for example
synchronization against multiple faults and faults causing block
allocation, depend on the correct implementation in the filesystem.  The
maturity of a given DAX implementation is filesystem specific.

Cc: &lt;stable@vger.kernel.org&gt;
Cc: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Cc: Matthew Wilcox &lt;willy@linux.intel.com&gt;
Cc: linux-ext4@vger.kernel.org
Cc: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Reported-by: Dave Chinner &lt;david@fromorbit.com&gt;
Acked-by: Jan Kara &lt;jack@suse.com&gt;
Signed-off-by: Dan Williams &lt;dan.j.williams@intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Similar to XFS warn when mounting DAX while it is still considered under
development.  Also, aspects of the DAX implementation, for example
synchronization against multiple faults and faults causing block
allocation, depend on the correct implementation in the filesystem.  The
maturity of a given DAX implementation is filesystem specific.

Cc: &lt;stable@vger.kernel.org&gt;
Cc: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Cc: Matthew Wilcox &lt;willy@linux.intel.com&gt;
Cc: linux-ext4@vger.kernel.org
Cc: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Reported-by: Dave Chinner &lt;david@fromorbit.com&gt;
Acked-by: Jan Kara &lt;jack@suse.com&gt;
Signed-off-by: Dan Williams &lt;dan.j.williams@intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-linus-3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs</title>
<updated>2015-11-14T02:02:30+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2015-11-14T02:02:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5d2eb548b309be34ecf3b91f0b7300a2b9d09b8c'/>
<id>5d2eb548b309be34ecf3b91f0b7300a2b9d09b8c</id>
<content type='text'>
Pull vfs xattr cleanups from Al Viro.

* 'for-linus-3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  f2fs: xattr simplifications
  squashfs: xattr simplifications
  9p: xattr simplifications
  xattr handlers: Pass handler to operations instead of flags
  jffs2: Add missing capability check for listing trusted xattrs
  hfsplus: Remove unused xattr handler list operations
  ubifs: Remove unused security xattr handler
  vfs: Fix the posix_acl_xattr_list return value
  vfs: Check attribute names in posix acl xattr handers
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull vfs xattr cleanups from Al Viro.

* 'for-linus-3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  f2fs: xattr simplifications
  squashfs: xattr simplifications
  9p: xattr simplifications
  xattr handlers: Pass handler to operations instead of flags
  jffs2: Add missing capability check for listing trusted xattrs
  hfsplus: Remove unused xattr handler list operations
  ubifs: Remove unused security xattr handler
  vfs: Fix the posix_acl_xattr_list return value
  vfs: Check attribute names in posix acl xattr handers
</pre>
</div>
</content>
</entry>
<entry>
<title>xattr handlers: Pass handler to operations instead of flags</title>
<updated>2015-11-14T01:34:32+00:00</updated>
<author>
<name>Andreas Gruenbacher</name>
<email>agruenba@redhat.com</email>
</author>
<published>2015-10-04T17:18:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d9a82a04033f87bbd06efb29f78c0170a38154a8'/>
<id>d9a82a04033f87bbd06efb29f78c0170a38154a8</id>
<content type='text'>
The xattr_handler operations are currently all passed a file system
specific flags value which the operations can use to disambiguate between
different handlers; some file systems use that to distinguish the xattr
namespace, for example.  In some oprations, it would be useful to also have
access to the handler prefix.  To allow that, pass a pointer to the handler
to operations instead of the flags value alone.

Signed-off-by: Andreas Gruenbacher &lt;agruenba@redhat.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The xattr_handler operations are currently all passed a file system
specific flags value which the operations can use to disambiguate between
different handlers; some file systems use that to distinguish the xattr
namespace, for example.  In some oprations, it would be useful to also have
access to the handler prefix.  To allow that, pass a pointer to the handler
to operations instead of the flags value alone.

Signed-off-by: Andreas Gruenbacher &lt;agruenba@redhat.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'akpm' (patches from Andrew)</title>
<updated>2015-11-10T05:05:13+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2015-11-10T05:05:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=bd4f203e433387d39be404b67ad02acf6f76b7bc'/>
<id>bd4f203e433387d39be404b67ad02acf6f76b7bc</id>
<content type='text'>
Merge third patch-bomb from Andrew Morton:
 "We're pretty much done over here - I'm still waiting for a nouveau
  merge so I can cleanly finish up Christoph's dma-mapping rework.

   - bunch of small misc stuff

   - fold abs64() into abs(), remove abs64()

   - new_valid_dev() cleanups

   - binfmt_elf_fdpic feature work"

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;: (24 commits)
  fs/binfmt_elf_fdpic.c: provide NOMMU loader for regular ELF binaries
  fs/stat.c: remove unnecessary new_valid_dev() check
  fs/reiserfs/namei.c: remove unnecessary new_valid_dev() check
  fs/nilfs2/namei.c: remove unnecessary new_valid_dev() check
  fs/ncpfs/dir.c: remove unnecessary new_valid_dev() check
  fs/jfs: remove unnecessary new_valid_dev() checks
  fs/hpfs/namei.c: remove unnecessary new_valid_dev() check
  fs/f2fs/namei.c: remove unnecessary new_valid_dev() check
  fs/ext2/namei.c: remove unnecessary new_valid_dev() check
  fs/exofs/namei.c: remove unnecessary new_valid_dev() check
  fs/btrfs/inode.c: remove unnecessary new_valid_dev() check
  fs/9p: remove unnecessary new_valid_dev() checks
  include/linux/kdev_t.h: old/new_valid_dev() can return bool
  include/linux/kdev_t.h: remove unused huge_valid_dev()
  kmap_atomic_to_page() has no users, remove it
  drivers/scsi/cxgbi: fix build with EXTRA_CFLAGS
  dma: remove external references to dma_supported
  Documentation/sysctl/vm.txt: fix misleading code reference of overcommit_memory
  remove abs64()
  kernel.h: make abs() work with 64-bit types
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Merge third patch-bomb from Andrew Morton:
 "We're pretty much done over here - I'm still waiting for a nouveau
  merge so I can cleanly finish up Christoph's dma-mapping rework.

   - bunch of small misc stuff

   - fold abs64() into abs(), remove abs64()

   - new_valid_dev() cleanups

   - binfmt_elf_fdpic feature work"

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;: (24 commits)
  fs/binfmt_elf_fdpic.c: provide NOMMU loader for regular ELF binaries
  fs/stat.c: remove unnecessary new_valid_dev() check
  fs/reiserfs/namei.c: remove unnecessary new_valid_dev() check
  fs/nilfs2/namei.c: remove unnecessary new_valid_dev() check
  fs/ncpfs/dir.c: remove unnecessary new_valid_dev() check
  fs/jfs: remove unnecessary new_valid_dev() checks
  fs/hpfs/namei.c: remove unnecessary new_valid_dev() check
  fs/f2fs/namei.c: remove unnecessary new_valid_dev() check
  fs/ext2/namei.c: remove unnecessary new_valid_dev() check
  fs/exofs/namei.c: remove unnecessary new_valid_dev() check
  fs/btrfs/inode.c: remove unnecessary new_valid_dev() check
  fs/9p: remove unnecessary new_valid_dev() checks
  include/linux/kdev_t.h: old/new_valid_dev() can return bool
  include/linux/kdev_t.h: remove unused huge_valid_dev()
  kmap_atomic_to_page() has no users, remove it
  drivers/scsi/cxgbi: fix build with EXTRA_CFLAGS
  dma: remove external references to dma_supported
  Documentation/sysctl/vm.txt: fix misleading code reference of overcommit_memory
  remove abs64()
  kernel.h: make abs() work with 64-bit types
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>fs/ext2/namei.c: remove unnecessary new_valid_dev() check</title>
<updated>2015-11-09T23:11:24+00:00</updated>
<author>
<name>Yaowei Bai</name>
<email>bywxiaobai@163.com</email>
</author>
<published>2015-11-09T22:58:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d7df00072e64f972e0f7eb4fea78eed2da9c0e59'/>
<id>d7df00072e64f972e0f7eb4fea78eed2da9c0e59</id>
<content type='text'>
new_valid_dev() always returns 1, so the !new_valid_dev() check is not
needed.  Remove it.

Signed-off-by: Yaowei Bai &lt;bywxiaobai@163.com&gt;
Cc: Alexander Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Jan Kara &lt;jack@suse.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
new_valid_dev() always returns 1, so the !new_valid_dev() check is not
needed.  Remove it.

Signed-off-by: Yaowei Bai &lt;bywxiaobai@163.com&gt;
Cc: Alexander Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Jan Kara &lt;jack@suse.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext2: Add locking for DAX faults</title>
<updated>2015-10-19T12:40:54+00:00</updated>
<author>
<name>Ross Zwisler</name>
<email>ross.zwisler@linux.intel.com</email>
</author>
<published>2015-10-13T22:25:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5726b27b09cc92452b543764899a07e7c8037edd'/>
<id>5726b27b09cc92452b543764899a07e7c8037edd</id>
<content type='text'>
Add locking to ensure that DAX faults are isolated from ext2 operations
that modify the data blocks allocation for an inode.  This is intended to
be analogous to the work being done in XFS by Dave Chinner:

http://www.spinics.net/lists/linux-fsdevel/msg90260.html

Compared with XFS the ext2 case is greatly simplified by the fact that ext2
already allocates and zeros new blocks before they are returned as part of
ext2_get_block(), so DAX doesn't need to worry about getting unmapped or
unwritten buffer heads.

This means that the only work we need to do in ext2 is to isolate the DAX
faults from inode block allocation changes.  I believe this just means that
we need to isolate the DAX faults from truncate operations.

The newly introduced dax_sem is intended to replicate the protection
offered by i_mmaplock in XFS.  In addition to truncate the i_mmaplock also
protects XFS operations like hole punching, fallocate down, extent
manipulation IOCTLS like xfs_ioc_space() and extent swapping.  Truncate is
the only one of these operations supported by ext2.

Signed-off-by: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.com&gt;
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Add locking to ensure that DAX faults are isolated from ext2 operations
that modify the data blocks allocation for an inode.  This is intended to
be analogous to the work being done in XFS by Dave Chinner:

http://www.spinics.net/lists/linux-fsdevel/msg90260.html

Compared with XFS the ext2 case is greatly simplified by the fact that ext2
already allocates and zeros new blocks before they are returned as part of
ext2_get_block(), so DAX doesn't need to worry about getting unmapped or
unwritten buffer heads.

This means that the only work we need to do in ext2 is to isolate the DAX
faults from inode block allocation changes.  I believe this just means that
we need to isolate the DAX faults from truncate operations.

The newly introduced dax_sem is intended to replicate the protection
offered by i_mmaplock in XFS.  In addition to truncate the i_mmaplock also
protects XFS operations like hole punching, fallocate down, extent
manipulation IOCTLS like xfs_ioc_space() and extent swapping.  Truncate is
the only one of these operations supported by ext2.

Signed-off-by: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Signed-off-by: Jan Kara &lt;jack@suse.com&gt;
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