If a filesystem supports POSIX ACL's, the VFS layer expects the filesystem 
to do POSIX ACL checks on any files not owned by the caller, and it does 
this for every single pathname component that it looks up.

That obviously can be pretty expensive if the filesystem isn't careful 
about it, especially with locking. That's doubly sad, since the common 
case tends to be that there are no ACL's associated with the files in 
question.

ext3 already caches the ACL data so that it doesn't have to look it up 
over and over again, but it does so by taking the inode->i_lock spinlock 
on every lookup. Which is a noticeable overhead even if it's a private 
lock, especially on CPU's where the serialization is expensive (eg Intel 
Netburst aka 'P4').

For the special case of not actually having any ACL's, all that locking is 
unnecessary. Even if somebody else were to be changing the ACL's on 
another CPU, we simply don't care - if we've seen a NULL ACL, we might as 
well use it.

So just load the ACL speculatively without any locking, and if it was 
NULL, just use it. If it's non-NULL (either because we had a cached 
entry, or because the cache hasn't been filled in at all), it means that 
we'll need to get the lock and re-load it properly.

This is noticeable even on Nehalem, which does locking quite well (much 
better than P4). From lmbench:

	Processor, Processes - times in microseconds - smaller is better
	--------------------------------------------------------------------
	Host                 OS  Mhz null null      open slct fork exec sh  
	                             call  I/O stat clos TCP  proc proc proc
	--------- ------------- ---- ---- ---- ---- ---- ---- ---- ---- ----
 - before:
	nehalem.l Linux 2.6.30- 3193 0.04 0.09 0.95 1.45 2.18 69.1 273. 1141
	nehalem.l Linux 2.6.30- 3193 0.04 0.09 0.95 1.48 2.28 69.9 253. 1140
	nehalem.l Linux 2.6.30- 3193 0.04 0.10 0.95 1.42 2.19 68.6 284. 1141
 - after:
	nehalem.l Linux 2.6.30- 3193 0.04 0.09 0.92 1.44 2.12 68.3 282. 1094
	nehalem.l Linux 2.6.30- 3193 0.04 0.09 0.92 1.39 2.20 67.0 308. 1123
	nehalem.l Linux 2.6.30- 3193 0.04 0.09 0.92 1.39 2.36 67.4 293. 1148

where you can see what appears to be a roughly 3% improvement in stat
and open/close latencies from just the removal of the locking overhead. 

Of course, this only matters for files you don't own (the owner never 
needs to do the ACL checks), but that's the common case for libraries, 
header files, and executables. As well as for the base components of any 
absolute pathname, even if you are the owner of the final file.

[ At some point we probably want to move this ACL caching logic entirely
  into the VFS layer (and only call down to the filesystem when
  uncached), but in the meantime this improves ext3 a bit.

  A similar fix to btrfs makes a much bigger difference (15x improvement
  in lmbench) due to broken caching. ]
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Acked-by: NJan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>

current->fs->umask is what most of fs_struct users are doing.
Put that into a helper function.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

* kill nameidata * argument; map the 3 bits in ->flags anybody cares
  about to new MAY_... ones and pass with the mask.
* kill redundant gfs2_iop_permission()
* sanitize ecryptfs_permission()
* fix remaining places where ->permission() instances might barf on new
  MAY_... found in mask.

The obvious next target in that direction is permission(9)

folded fix for nfs_permission() breakage from Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

There are several places where we make allocations with GFP_KERNEL while under
a transaction, which could lead to an assertion panic or lockup if under
memory pressure.  This patch switches these problem areas to use GFP_NOFS to
keep these problems from happening.
Signed-off-by: NJosef Bacik <jbacik@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce is_owner_or_cap() macro in fs.h, and convert over relevant
users to it. This is done because we want to avoid bugs in the future
where we check for only effective fsuid of the current task against a
file's owning uid, without simultaneously checking for CAP_FOWNER as
well, thus violating its semantics.
[ XFS uses special macros and structures, and in general looked ...
untouchable, so we leave it alone -- but it has been looked over. ]

The (current->fsuid != inode->i_uid) check in generic_permission() and
exec_permission_lite() is left alone, because those operations are
covered by CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH. Similarly operations
falling under the purview of CAP_CHOWN and CAP_LEASE are also left alone.
Signed-off-by: NSatyam Sharma <ssatyam@cse.iitk.ac.in>
Cc: Al Viro <viro@ftp.linux.org.uk>
Acked-by: NSerge E. Hallyn <serge@hallyn.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

* Removing useless casts
* Removing useless wrapper
* Conversion from kmalloc+memset to kzalloc
Signed-off-by: NPanagiotis Issaris <takis@issaris.org>
Acked-by: NDave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

More white space cleanups in preparation of cloning ext4 from ext3.
Removing spaces that precede a tab.
Signed-off-by: NDave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There is a code path that passed size to ext2_xattr_set
(ext3_xattr_set_handle) before initializing it.  The callees don't use the
value in that case, but gcc cannot tell.  Always initialize size to get rid
of the warnings.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs: Use <linux/capability.h> where capable() is used.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NTim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch converts the inode semaphore to a mutex. I have tested it on
XFS and compiled as much as one can consider on an ia64. Anyway your
luck with it might be different.
Modified-by: NIngo Molnar <mingo@elte.hu>

(finished the conversion)
Signed-off-by: NJes Sorensen <jes@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Use improved credits estimates for quota operations.  Also reserve a space
for a quota operation in a transaction only if filesystem was mounted with
some quota options.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This file duplicates <linux/posix_acl_xattr.h>, using slightly different
names.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

)


From: Andreas Gruenbacher <agruen@suse.de>

ext[23]_get_acl will return an error when reading the attribute fails or
out-of-memory occurs.  Catch this case.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!