<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/include/uapi/linux/magic.h, branch v4.6-rc3</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>Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs</title>
<updated>2016-01-21T20:20:46+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2016-01-21T20:20:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e9f57ebcba563e0cd532926cab83c92bb4d79360'/>
<id>e9f57ebcba563e0cd532926cab83c92bb4d79360</id>
<content type='text'>
Pull overlayfs updates from Miklos Szeredi:
 "This contains several bug fixes and a new mount option
  'default_permissions' that allows read-only exported NFS
  filesystems to be used as lower layer"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: check dentry positiveness in ovl_cleanup_whiteouts()
  ovl: setattr: check permissions before copy-up
  ovl: root: copy attr
  ovl: move super block magic number to magic.h
  ovl: use a minimal buffer in ovl_copy_xattr
  ovl: allow zero size xattr
  ovl: default permissions
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull overlayfs updates from Miklos Szeredi:
 "This contains several bug fixes and a new mount option
  'default_permissions' that allows read-only exported NFS
  filesystems to be used as lower layer"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: check dentry positiveness in ovl_cleanup_whiteouts()
  ovl: setattr: check permissions before copy-up
  ovl: root: copy attr
  ovl: move super block magic number to magic.h
  ovl: use a minimal buffer in ovl_copy_xattr
  ovl: allow zero size xattr
  ovl: default permissions
</pre>
</div>
</content>
</entry>
<entry>
<title>cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type</title>
<updated>2015-11-16T16:13:34+00:00</updated>
<author>
<name>Tejun Heo</name>
<email>tj@kernel.org</email>
</author>
<published>2015-11-16T16:13:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=67e9c74b8a873408c27ac9a8e4c1d1c8d72c93ff'/>
<id>67e9c74b8a873408c27ac9a8e4c1d1c8d72c93ff</id>
<content type='text'>
With major controllers - cpu, memory and io - shaping up for the
unified hierarchy, cgroup2 is about ready to be, gradually, released
into the wild.  Replace __DEVEL__sane_behavior flag which was used to
select the unified hierarchy with a separate filesystem type "cgroup2"
so that unified hierarchy can be mounted as follows.

  mount -t cgroup2 none $MOUNT_POINT

The cgroup2 fs has its own magic number - 0x63677270 ("cgrp").

v2: Assign a different magic number to cgroup2 fs.

Signed-off-by: Tejun Heo &lt;tj@kernel.org&gt;
Acked-by: Li Zefan &lt;lizefan@huawei.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With major controllers - cpu, memory and io - shaping up for the
unified hierarchy, cgroup2 is about ready to be, gradually, released
into the wild.  Replace __DEVEL__sane_behavior flag which was used to
select the unified hierarchy with a separate filesystem type "cgroup2"
so that unified hierarchy can be mounted as follows.

  mount -t cgroup2 none $MOUNT_POINT

The cgroup2 fs has its own magic number - 0x63677270 ("cgrp").

v2: Assign a different magic number to cgroup2 fs.

Signed-off-by: Tejun Heo &lt;tj@kernel.org&gt;
Acked-by: Li Zefan &lt;lizefan@huawei.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ovl: move super block magic number to magic.h</title>
<updated>2015-11-10T16:13:35+00:00</updated>
<author>
<name>Stephen Hemminger</name>
<email>stephen@networkplumber.org</email>
</author>
<published>2015-11-04T18:59:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=257f871993474e2bde6c497b54022c362cf398e1'/>
<id>257f871993474e2bde6c497b54022c362cf398e1</id>
<content type='text'>
The overlayfs file system is not recognized by programs
like tail because the magic number is not in standard header location.

Move it so that the value will propagate on for the GNU library
and utilities. Needs to go in the fstatfs manual page as well.

Signed-off-by: Stephen Hemminger &lt;stephen@networkplumber.org&gt;
Signed-off-by: Miklos Szeredi &lt;miklos@szeredi.hu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The overlayfs file system is not recognized by programs
like tail because the magic number is not in standard header location.

Move it so that the value will propagate on for the GNU library
and utilities. Needs to go in the fstatfs manual page as well.

Signed-off-by: Stephen Hemminger &lt;stephen@networkplumber.org&gt;
Signed-off-by: Miklos Szeredi &lt;miklos@szeredi.hu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: add support for persistent maps/progs</title>
<updated>2015-11-03T03:48:39+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2015-10-29T13:58:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=b2197755b2633e164a439682fb05a9b5ea48f706'/>
<id>b2197755b2633e164a439682fb05a9b5ea48f706</id>
<content type='text'>
This work adds support for "persistent" eBPF maps/programs. The term
"persistent" is to be understood that maps/programs have a facility
that lets them survive process termination. This is desired by various
eBPF subsystem users.

Just to name one example: tc classifier/action. Whenever tc parses
the ELF object, extracts and loads maps/progs into the kernel, these
file descriptors will be out of reach after the tc instance exits.
So a subsequent tc invocation won't be able to access/relocate on this
resource, and therefore maps cannot easily be shared, f.e. between the
ingress and egress networking data path.

The current workaround is that Unix domain sockets (UDS) need to be
instrumented in order to pass the created eBPF map/program file
descriptors to a third party management daemon through UDS' socket
passing facility. This makes it a bit complicated to deploy shared
eBPF maps or programs (programs f.e. for tail calls) among various
processes.

We've been brainstorming on how we could tackle this issue and various
approches have been tried out so far, which can be read up further in
the below reference.

The architecture we eventually ended up with is a minimal file system
that can hold map/prog objects. The file system is a per mount namespace
singleton, and the default mount point is /sys/fs/bpf/. Any subsequent
mounts within a given namespace will point to the same instance. The
file system allows for creating a user-defined directory structure.
The objects for maps/progs are created/fetched through bpf(2) with
two new commands (BPF_OBJ_PIN/BPF_OBJ_GET). I.e. a bpf file descriptor
along with a pathname is being passed to bpf(2) that in turn creates
(we call it eBPF object pinning) the file system nodes. Only the pathname
is being passed to bpf(2) for getting a new BPF file descriptor to an
existing node. The user can use that to access maps and progs later on,
through bpf(2). Removal of file system nodes is being managed through
normal VFS functions such as unlink(2), etc. The file system code is
kept to a very minimum and can be further extended later on.

The next step I'm working on is to add dump eBPF map/prog commands
to bpf(2), so that a specification from a given file descriptor can
be retrieved. This can be used by things like CRIU but also applications
can inspect the meta data after calling BPF_OBJ_GET.

Big thanks also to Alexei and Hannes who significantly contributed
in the design discussion that eventually let us end up with this
architecture here.

Reference: https://lkml.org/lkml/2015/10/15/925
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: Hannes Frederic Sowa &lt;hannes@stressinduktion.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This work adds support for "persistent" eBPF maps/programs. The term
"persistent" is to be understood that maps/programs have a facility
that lets them survive process termination. This is desired by various
eBPF subsystem users.

Just to name one example: tc classifier/action. Whenever tc parses
the ELF object, extracts and loads maps/progs into the kernel, these
file descriptors will be out of reach after the tc instance exits.
So a subsequent tc invocation won't be able to access/relocate on this
resource, and therefore maps cannot easily be shared, f.e. between the
ingress and egress networking data path.

The current workaround is that Unix domain sockets (UDS) need to be
instrumented in order to pass the created eBPF map/program file
descriptors to a third party management daemon through UDS' socket
passing facility. This makes it a bit complicated to deploy shared
eBPF maps or programs (programs f.e. for tail calls) among various
processes.

We've been brainstorming on how we could tackle this issue and various
approches have been tried out so far, which can be read up further in
the below reference.

The architecture we eventually ended up with is a minimal file system
that can hold map/prog objects. The file system is a per mount namespace
singleton, and the default mount point is /sys/fs/bpf/. Any subsequent
mounts within a given namespace will point to the same instance. The
file system allows for creating a user-defined directory structure.
The objects for maps/progs are created/fetched through bpf(2) with
two new commands (BPF_OBJ_PIN/BPF_OBJ_GET). I.e. a bpf file descriptor
along with a pathname is being passed to bpf(2) that in turn creates
(we call it eBPF object pinning) the file system nodes. Only the pathname
is being passed to bpf(2) for getting a new BPF file descriptor to an
existing node. The user can use that to access maps and progs later on,
through bpf(2). Removal of file system nodes is being managed through
normal VFS functions such as unlink(2), etc. The file system code is
kept to a very minimum and can be further extended later on.

The next step I'm working on is to add dump eBPF map/prog commands
to bpf(2), so that a specification from a given file descriptor can
be retrieved. This can be used by things like CRIU but also applications
can inspect the meta data after calling BPF_OBJ_GET.

Big thanks also to Alexei and Hannes who significantly contributed
in the design discussion that eventually let us end up with this
architecture here.

Reference: https://lkml.org/lkml/2015/10/15/925
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: Hannes Frederic Sowa &lt;hannes@stressinduktion.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>tracefs: Add new tracefs file system</title>
<updated>2015-02-03T17:48:40+00:00</updated>
<author>
<name>Steven Rostedt (Red Hat)</name>
<email>rostedt@goodmis.org</email>
</author>
<published>2015-01-20T16:36:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=4282d60689d4f21b40692029080440cc58e8a17d'/>
<id>4282d60689d4f21b40692029080440cc58e8a17d</id>
<content type='text'>
Add a separate file system to handle the tracing directory. Currently it
is part of debugfs, but that is starting to show its limits.

One thing is that in order to access the tracing infrastructure, you need
to mount debugfs. As that includes debugging from all sorts of sub systems
in the kernel, it is not considered advisable to mount such an all
encompassing debugging system.

Having the tracing system in its own file systems gives access to the
tracing sub system without needing to include all other systems.

Another problem with tracing using the debugfs system is that the
instances use mkdir to create sub buffers. debugfs does not support mkdir
from userspace so to implement it, special hacks were used. By controlling
the file system that the tracing infrastructure uses, this can be properly
done without hacks.

Signed-off-by: Steven Rostedt &lt;rostedt@goodmis.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add a separate file system to handle the tracing directory. Currently it
is part of debugfs, but that is starting to show its limits.

One thing is that in order to access the tracing infrastructure, you need
to mount debugfs. As that includes debugging from all sorts of sub systems
in the kernel, it is not considered advisable to mount such an all
encompassing debugging system.

Having the tracing system in its own file systems gives access to the
tracing sub system without needing to include all other systems.

Another problem with tracing using the debugfs system is that the
instances use mkdir to create sub buffers. debugfs does not support mkdir
from userspace so to implement it, special hacks were used. By controlling
the file system that the tracing infrastructure uses, this can be properly
done without hacks.

Signed-off-by: Steven Rostedt &lt;rostedt@goodmis.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>take the targets of /proc/*/ns/* symlinks to separate fs</title>
<updated>2014-12-11T02:30:20+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2014-11-01T14:57:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e149ed2b805fefdccf7ccdfc19eca22fdd4514ac'/>
<id>e149ed2b805fefdccf7ccdfc19eca22fdd4514ac</id>
<content type='text'>
New pseudo-filesystem: nsfs.  Targets of /proc/*/ns/* live there now.
It's not mountable (not even registered, so it's not in /proc/filesystems,
etc.).  Files on it *are* bindable - we explicitly permit that in do_loopback().

This stuff lives in fs/nsfs.c now; proc_ns_fget() moved there as well.
get_proc_ns() is a macro now (it's simply returning -&gt;i_private; would
have been an inline, if not for header ordering headache).
proc_ns_inode() is an ex-parrot.  The interface used in procfs is
ns_get_path(path, task, ops) and ns_get_name(buf, size, task, ops).

Dentries and inodes are never hashed; a non-counting reference to dentry
is stashed in ns_common (removed by -&gt;d_prune()) and reused by ns_get_path()
if present.  See ns_get_path()/ns_prune_dentry/nsfs_evict() for details
of that mechanism.

As the result, proc_ns_follow_link() has stopped poking in nd-&gt;path.mnt;
it does nd_jump_link() on a consistent &lt;vfsmount,dentry&gt; pair it gets
from ns_get_path().

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>
New pseudo-filesystem: nsfs.  Targets of /proc/*/ns/* live there now.
It's not mountable (not even registered, so it's not in /proc/filesystems,
etc.).  Files on it *are* bindable - we explicitly permit that in do_loopback().

This stuff lives in fs/nsfs.c now; proc_ns_fget() moved there as well.
get_proc_ns() is a macro now (it's simply returning -&gt;i_private; would
have been an inline, if not for header ordering headache).
proc_ns_inode() is an ex-parrot.  The interface used in procfs is
ns_get_path(path, task, ops) and ns_get_name(buf, size, task, ops).

Dentries and inodes are never hashed; a non-counting reference to dentry
is stashed in ns_common (removed by -&gt;d_prune()) and reused by ns_get_path()
if present.  See ns_get_path()/ns_prune_dentry/nsfs_evict() for details
of that mechanism.

As the result, proc_ns_follow_link() has stopped poking in nd-&gt;path.mnt;
it does nd_jump_link() on a consistent &lt;vfsmount,dentry&gt; pair it gets
from ns_get_path().

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Btrfs: add tests for find_lock_delalloc_range</title>
<updated>2013-11-12T02:56:51+00:00</updated>
<author>
<name>Josef Bacik</name>
<email>jbacik@fusionio.com</email>
</author>
<published>2013-10-09T16:00:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=294e30fee35d3151d100cfe59e839c2dbc16a374'/>
<id>294e30fee35d3151d100cfe59e839c2dbc16a374</id>
<content type='text'>
So both Liu and I made huge messes of find_lock_delalloc_range trying to fix
stuff, me first by fixing extent size, then him by fixing something I broke and
then me again telling him to fix it a different way.  So this is obviously a
candidate for some testing.  This patch adds a pseudo fs so we can allocate fake
inodes for tests that need an inode or pages.  Then it addes a bunch of tests to
make sure find_lock_delalloc_range is acting the way it is supposed to.  With
this patch and all of our previous patches to find_lock_delalloc_range I am sure
it is working as expected now.  Thanks,

Signed-off-by: Josef Bacik &lt;jbacik@fusionio.com&gt;
Signed-off-by: Chris Mason &lt;chris.mason@fusionio.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
So both Liu and I made huge messes of find_lock_delalloc_range trying to fix
stuff, me first by fixing extent size, then him by fixing something I broke and
then me again telling him to fix it a different way.  So this is obviously a
candidate for some testing.  This patch adds a pseudo fs so we can allocate fake
inodes for tests that need an inode or pages.  Then it addes a bunch of tests to
make sure find_lock_delalloc_range is acting the way it is supposed to.  With
this patch and all of our previous patches to find_lock_delalloc_range I am sure
it is working as expected now.  Thanks,

Signed-off-by: Josef Bacik &lt;jbacik@fusionio.com&gt;
Signed-off-by: Chris Mason &lt;chris.mason@fusionio.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>hostfs: move HOSTFS_SUPER_MAGIC to &lt;linux/magic.h&gt;</title>
<updated>2013-05-04T19:48:44+00:00</updated>
<author>
<name>James Hogan</name>
<email>james.hogan@imgtec.com</email>
</author>
<published>2013-03-27T10:47:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2b3b9bb03a9fb1e4c72947cc235771c6455ec7c9'/>
<id>2b3b9bb03a9fb1e4c72947cc235771c6455ec7c9</id>
<content type='text'>
Move HOSTFS_SUPER_MAGIC to &lt;linux/magic.h&gt; to be with it's magical
friends from other file systems.

Reported-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Signed-off-by: James Hogan &lt;james.hogan@imgtec.com&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>
Move HOSTFS_SUPER_MAGIC to &lt;linux/magic.h&gt; to be with it's magical
friends from other file systems.

Reported-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Signed-off-by: James Hogan &lt;james.hogan@imgtec.com&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>smack: SMACK_MAGIC to include/uapi/linux/magic.h</title>
<updated>2013-03-19T21:16:15+00:00</updated>
<author>
<name>Jarkko Sakkinen</name>
<email>jarkko.sakkinen@iki.fi</email>
</author>
<published>2012-11-06T08:17:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=cee7e443344a3845e5b9111614b41e0b1afb60ce'/>
<id>cee7e443344a3845e5b9111614b41e0b1afb60ce</id>
<content type='text'>
SMACK_MAGIC moved to a proper place for easy user space access
(i.e. libsmack).

Signed-off-by: Jarkko Sakkinen &lt;jarkko.sakkinen@iki.fi&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
SMACK_MAGIC moved to a proper place for easy user space access
(i.e. libsmack).

Signed-off-by: Jarkko Sakkinen &lt;jarkko.sakkinen@iki.fi&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'for-3.8-merge' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs</title>
<updated>2012-12-20T21:54:52+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-12-20T21:54:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a13eea6bd9ee62ceacfc5243d54c84396bc86cb4'/>
<id>a13eea6bd9ee62ceacfc5243d54c84396bc86cb4</id>
<content type='text'>
Pull new F2FS filesystem from Jaegeuk Kim:
 "Introduce a new file system, Flash-Friendly File System (F2FS), to
  Linux 3.8.

  Highlights:
   - Add initial f2fs source codes
   - Fix an endian conversion bug
   - Fix build failures on random configs
   - Fix the power-off-recovery routine
   - Minor cleanup, coding style, and typos patches"

From the Kconfig help text:

  F2FS is based on Log-structured File System (LFS), which supports
  versatile "flash-friendly" features. The design has been focused on
  addressing the fundamental issues in LFS, which are snowball effect
  of wandering tree and high cleaning overhead.

  Since flash-based storages show different characteristics according to
  the internal geometry or flash memory management schemes aka FTL, F2FS
  and tools support various parameters not only for configuring on-disk
  layout, but also for selecting allocation and cleaning algorithms.

and there's an article by Neil Brown about it on lwn.net:

  http://lwn.net/Articles/518988/

* tag 'for-3.8-merge' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (36 commits)
  f2fs: fix tracking parent inode number
  f2fs: cleanup the f2fs_bio_alloc routine
  f2fs: introduce accessor to retrieve number of dentry slots
  f2fs: remove redundant call to f2fs_put_page in delete entry
  f2fs: make use of GFP_F2FS_ZERO for setting gfp_mask
  f2fs: rewrite f2fs_bio_alloc to make it simpler
  f2fs: fix a typo in f2fs documentation
  f2fs: remove unused variable
  f2fs: move error condition for mkdir at proper place
  f2fs: remove unneeded initialization
  f2fs: check read only condition before beginning write out
  f2fs: remove unneeded memset from init_once
  f2fs: show error in case of invalid mount arguments
  f2fs: fix the compiler warning for uninitialized use of variable
  f2fs: resolve build failures
  f2fs: adjust kernel coding style
  f2fs: fix endian conversion bugs reported by sparse
  f2fs: remove unneeded version.h header file from f2fs.h
  f2fs: update the f2fs document
  f2fs: update Kconfig and Makefile
  ...
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Pull new F2FS filesystem from Jaegeuk Kim:
 "Introduce a new file system, Flash-Friendly File System (F2FS), to
  Linux 3.8.

  Highlights:
   - Add initial f2fs source codes
   - Fix an endian conversion bug
   - Fix build failures on random configs
   - Fix the power-off-recovery routine
   - Minor cleanup, coding style, and typos patches"

From the Kconfig help text:

  F2FS is based on Log-structured File System (LFS), which supports
  versatile "flash-friendly" features. The design has been focused on
  addressing the fundamental issues in LFS, which are snowball effect
  of wandering tree and high cleaning overhead.

  Since flash-based storages show different characteristics according to
  the internal geometry or flash memory management schemes aka FTL, F2FS
  and tools support various parameters not only for configuring on-disk
  layout, but also for selecting allocation and cleaning algorithms.

and there's an article by Neil Brown about it on lwn.net:

  http://lwn.net/Articles/518988/

* tag 'for-3.8-merge' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (36 commits)
  f2fs: fix tracking parent inode number
  f2fs: cleanup the f2fs_bio_alloc routine
  f2fs: introduce accessor to retrieve number of dentry slots
  f2fs: remove redundant call to f2fs_put_page in delete entry
  f2fs: make use of GFP_F2FS_ZERO for setting gfp_mask
  f2fs: rewrite f2fs_bio_alloc to make it simpler
  f2fs: fix a typo in f2fs documentation
  f2fs: remove unused variable
  f2fs: move error condition for mkdir at proper place
  f2fs: remove unneeded initialization
  f2fs: check read only condition before beginning write out
  f2fs: remove unneeded memset from init_once
  f2fs: show error in case of invalid mount arguments
  f2fs: fix the compiler warning for uninitialized use of variable
  f2fs: resolve build failures
  f2fs: adjust kernel coding style
  f2fs: fix endian conversion bugs reported by sparse
  f2fs: remove unneeded version.h header file from f2fs.h
  f2fs: update the f2fs document
  f2fs: update Kconfig and Makefile
  ...
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