linux-toradex.git/include/linux/fs.h, branch tegra-11.2.9

fs: {lock,unlock}_flocks() stubs to prepare for BKL removal

2010-09-22T00:27:44+00:00

The lock structs are currently protected by the BKL, but are accessed by
code in fs/locks.c and misc file system and DLM code.  These stubs will
allow all users to switch to the new interface before the implementation
is changed to a spinlock.

Acked-by: Arnd Bergmann 
Signed-off-by: Sage Weil 
Signed-off-by: Linus Torvalds

fs: scale files_lock

2010-08-18T12:35:48+00:00

fs: scale files_lock

Improve scalability of files_lock by adding per-cpu, per-sb files lists,
protected with an lglock. The lglock provides fast access to the per-cpu lists
to add and remove files. It also provides a snapshot of all the per-cpu lists
(although this is very slow).

One difficulty with this approach is that a file can be removed from the list
by another CPU. We must track which per-cpu list the file is on with a new
variale in the file struct (packed into a hole on 64-bit archs). Scalability
could suffer if files are frequently removed from different cpu's list.

However loads with frequent removal of files imply short interval between
adding and removing the files, and the scheduler attempts to avoid moving
processes too far away. Also, even in the case of cross-CPU removal, the
hardware has much more opportunity to parallelise cacheline transfers with N
cachelines than with 1.

A worst-case test of 1 CPU allocating files subsequently being freed by N CPUs
degenerates to contending on a single lock, which is no worse than before. When
more than one CPU are allocating files, even if they are always freed by
different CPUs, there will be more parallelism than the single-lock case.

Testing results:

On a 2 socket, 8 core opteron, I measure the number of times the lock is taken
to remove the file, the number of times it is removed by the same CPU that
added it, and the number of times it is removed by the same node that added it.

Booting:    locks=  25049 cpu-hits=  23174 (92.5%) node-hits=  23945 (95.6%)
kbuild -j16 locks=2281913 cpu-hits=2208126 (96.8%) node-hits=2252674 (98.7%)
dbench 64   locks=4306582 cpu-hits=4287247 (99.6%) node-hits=4299527 (99.8%)

So a file is removed from the same CPU it was added by over 90% of the time.
It remains within the same node 95% of the time.

Tim Chen ran some numbers for a 64 thread Nehalem system performing a compile.

                throughput
2.6.34-rc2      24.5
+patch          24.9

                us      sys     idle    IO wait (in %)
2.6.34-rc2      51.25   28.25   17.25   3.25
+patch          53.75   18.5    19      8.75

So significantly less CPU time spent in kernel code, higher idle time and
slightly higher throughput.

Single threaded performance difference was within the noise of microbenchmarks.
That is not to say penalty does not exist, the code is larger and more memory
accesses required so it will be slightly slower.

Cc: linux-kernel@vger.kernel.org
Cc: Tim Chen 
Cc: Andi Kleen 
Signed-off-by: Nick Piggin 
Signed-off-by: Al Viro

tty: fix fu_list abuse

2010-08-18T12:35:47+00:00

tty: fix fu_list abuse

tty code abuses fu_list, which causes a bug in remount,ro handling.

If a tty device node is opened on a filesystem, then the last link to the inode
removed, the filesystem will be allowed to be remounted readonly. This is
because fs_may_remount_ro does not find the 0 link tty inode on the file sb
list (because the tty code incorrectly removed it to use for its own purpose).
This can result in a filesystem with errors after it is marked "clean".

Taking idea from Christoph's initial patch, allocate a tty private struct
at file->private_data and put our required list fields in there, linking
file and tty. This makes tty nodes behave the same way as other device nodes
and avoid meddling with the vfs, and avoids this bug.

The error handling is not trivial in the tty code, so for this bugfix, I take
the simple approach of using __GFP_NOFAIL and don't worry about memory errors.
This is not a problem because our allocator doesn't fail small allocs as a rule
anyway. So proper error handling is left as an exercise for tty hackers.

[ Arguably filesystem's device inode would ideally be divorced from the
driver's pseudo inode when it is opened, but in practice it's not clear whether
that will ever be worth implementing. ]

Cc: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig 
Cc: Alan Cox 
Cc: Greg Kroah-Hartman 
Signed-off-by: Nick Piggin 
Signed-off-by: Al Viro

fs: cleanup files_lock locking

2010-08-18T12:35:47+00:00

fs: cleanup files_lock locking

Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
manipulate the per-sb files list; unexport the files_lock spinlock.

Cc: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig 
Cc: Alan Cox 
Acked-by: Andi Kleen 
Acked-by: Greg Kroah-Hartman 
Signed-off-by: Nick Piggin 
Signed-off-by: Al Viro

remove SWRITE* I/O types

2010-08-18T05:09:01+00:00

These flags aren't real I/O types, but tell ll_rw_block to always
lock the buffer instead of giving up on a failed trylock.

Instead add a new write_dirty_buffer helper that implements this semantic
and use it from the existing SWRITE* callers.  Note that the ll_rw_block
code had a bug where it didn't promote WRITE_SYNC_PLUG properly, which
this patch fixes.

In the ufs code clean up the helper that used to call ll_rw_block
to mirror sync_dirty_buffer, which is the function it implements for
compound buffers.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Al Viro

Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing

2010-08-14T00:52:35+00:00

* 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing:
  bkl: Remove locked .ioctl file operation
  v4l: Remove reference to bkl ioctl in compat ioctl handling
  logfs: kill BKL

Mark arguments to certain syscalls as being const

2010-08-13T23:53:13+00:00

Mark arguments to certain system calls as being const where they should be but
aren't.  The list includes:

 (*) The filename arguments of various stat syscalls, execve(), various utimes
     syscalls and some mount syscalls.

 (*) The filename arguments of some syscall helpers relating to the above.

 (*) The buffer argument of various write syscalls.

Signed-off-by: David Howells 
Acked-by: David S. Miller 
Signed-off-by: Linus Torvalds

bkl: Remove locked .ioctl file operation

2010-08-13T22:24:24+00:00

The last user is gone, so we can safely remove this

Signed-off-by: Arnd Bergmann 
Cc: John Kacur 
Cc: Al Viro 
Cc: Thomas Gleixner 
Signed-off-by: Frederic Weisbecker

block: add secure discard

2010-08-12T15:43:30+00:00

Secure discard is the same as discard except that all copies of the
discarded sectors (perhaps created by garbage collection) must also be
erased.

Signed-off-by: Adrian Hunter 
Acked-by: Jens Axboe 
Cc: Kyungmin Park 
Cc: Madhusudhan Chikkature 
Cc: Christoph Hellwig 
Cc: Ben Gardiner 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

include/linux/fs.h: complete hexification of FMODE_* constants

2010-08-11T15:58:59+00:00

One straggler which was missed due to merge ordering issues.

Cc: Wu Fengguang 
Cc: Eric Paris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds