linux.git/fs/proc/generic.c, branch v4.6

proc: change proc_subdir_lock to a rwlock

2015-09-10T20:29:01+00:00

The proc_subdir_lock spinlock is used to allow only one task to make
change to the proc directory structure as well as looking up information
in it.  However, the information lookup part can actually be entered by
more than one task as the pde_get() and pde_put() reference count update
calls in the critical sections are atomic increment and decrement
respectively and so are safe with concurrent updates.

The x86 architecture has already used qrwlock which is fair and other
architectures like ARM are in the process of switching to qrwlock.  So
unfairness shouldn't be a concern in that conversion.

This patch changed the proc_subdir_lock to a rwlock in order to enable
concurrent lookup. The following functions were modified to take a
write lock:
 - proc_register()
 - remove_proc_entry()
 - remove_proc_subtree()

The following functions were modified to take a read lock:
 - xlate_proc_name()
 - proc_lookup_de()
 - proc_readdir_de()

A parallel /proc filesystem search with the "find" command (1000 threads)
was run on a 4-socket Haswell-EX box (144 threads).  Before the patch, the
parallel search took about 39s.  After the patch, the parallel find took
only 25s, a saving of about 14s.

The micro-benchmark that I used was artificial, but it was used to
reproduce an exit hanging problem that I saw in real application.  In
fact, only allow one task to do a lookup seems too limiting to me.

Signed-off-by: Waiman Long 
Acked-by: "Eric W. Biederman" 
Cc: Alexey Dobriyan 
Cc: Nicolas Dichtel 
Cc: Al Viro 
Cc: Scott J Norton 
Cc: Douglas Hatch 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc: Allow creating permanently empty directories that serve as mount points

2015-07-01T15:36:41+00:00

Add a new function proc_create_mount_point that when used to creates a
directory that can not be added to.

Add a new function is_empty_pde to test if a function is a mount
point.

Update the code to use make_empty_dir_inode when reporting
a permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Update /proc/openprom and /proc/fs/nfsd to be permanently empty directories.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman"

VFS: normal filesystems (and lustre): d_inode() annotations

2015-04-15T19:06:57+00:00

that's the bulk of filesystem drivers dealing with inodes of their own

Signed-off-by: David Howells 
Signed-off-by: Al Viro

procfs: fix race between symlink removals and traversals

2015-02-22T16:43:12+00:00

use_pde()/unuse_pde() in ->follow_link()/->put_link() resp.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2015-02-17T22:56:45+00:00

Pull misc VFS updates from Al Viro:
 "This cycle a lot of stuff sits on topical branches, so I'll be sending
  more or less one pull request per branch.

  This is the first pile; more to follow in a few.  In this one are
  several misc commits from early in the cycle (before I went for
  separate branches), plus the rework of mntput/dput ordering on umount,
  switching to use of fs_pin instead of convoluted games in
  namespace_unlock()"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  switch the IO-triggering parts of umount to fs_pin
  new fs_pin killing logics
  allow attaching fs_pin to a group not associated with some superblock
  get rid of the second argument of acct_kill()
  take count and rcu_head out of fs_pin
  dcache: let the dentry count go down to zero without taking d_lock
  pull bumping refcount into ->kill()
  kill pin_put()
  mode_t whack-a-mole: chelsio
  file->f_path.dentry is pinned down for as long as the file is open...
  get rid of lustre_dump_dentry()
  gut proc_register() a bit
  kill d_validate()
  ncpfs: get rid of d_validate() nonsense
  selinuxfs: don't open-code d_genocide()

fs: proc: use PDE() to get proc_dir_entry

2015-02-13T02:54:12+00:00

Use the PDE() helper to get proc_dir_entry instead of coding it directly.

Signed-off-by: Alexander Kuleshov 
Acked-by: Nicolas Dichtel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gut proc_register() a bit

2015-01-26T04:16:26+00:00

There are only 3 callers and quite a bit of that thing is executed
exactly in one of those.  Just lift it there...

Signed-off-by: Al Viro

fs/proc.c: use rb_entry_safe() instead of rb_entry()

2014-12-11T01:41:09+00:00

Better to use existing macro that rewriting them.

Signed-off-by: Nicolas Dichtel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

procfs: fix error handling of proc_register()

2014-12-11T01:41:09+00:00

proc_register() error paths are leaking inodes and directory refcounts.

Signed-off-by: Debabrata Banerjee 
Cc: Alexander Viro 
Acked-by: Nicolas Dichtel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/proc: use a rb tree for the directory entries

2014-12-11T01:41:09+00:00

When a lot of netdevices are created, one of the bottleneck is the
creation of proc entries.  This serie aims to accelerate this part.

The current implementation for the directories in /proc is using a single
linked list.  This is slow when handling directories with large numbers of
entries (eg netdevice-related entries when lots of tunnels are opened).

This patch replaces this linked list by a red-black tree.

Here are some numbers:

dummy30000.batch contains 30 000 times 'link add type dummy'.

Before the patch:
  $ time ip -b dummy30000.batch
  real    2m31.950s
  user    0m0.440s
  sys     2m21.440s
  $ time rmmod dummy
  real    1m35.764s
  user    0m0.000s
  sys     1m24.088s

After the patch:
  $ time ip -b dummy30000.batch
  real    2m0.874s
  user    0m0.448s
  sys     1m49.720s
  $ time rmmod dummy
  real    1m13.988s
  user    0m0.000s
  sys     1m1.008s

The idea of improving this part was suggested by Thierry Herbelot.

[akpm@linux-foundation.org: initialise proc_root.subdir at compile time]
Signed-off-by: Nicolas Dichtel 
Acked-by: David S. Miller 
Cc: Thierry Herbelot .
Acked-by: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds