linux-toradex.git/Documentation, branch v2.6.29.4

mm: close page_mkwrite races

2009-05-18T23:35:04+00:00

commit b827e496c893de0c0f142abfaeb8730a2fd6b37f upstream.

Change page_mkwrite to allow implementations to return with the page
locked, and also change it's callers (in page fault paths) to hold the
lock until the page is marked dirty.  This allows the filesystem to have
full control of page dirtying events coming from the VM.

Rather than simply hold the page locked over the page_mkwrite call, we
call page_mkwrite with the page unlocked and allow callers to return with
it locked, so filesystems can avoid LOR conditions with page lock.

The problem with the current scheme is this: a filesystem that wants to
associate some metadata with a page as long as the page is dirty, will
perform this manipulation in its ->page_mkwrite.  It currently then must
return with the page unlocked and may not hold any other locks (according
to existing page_mkwrite convention).

In this window, the VM could write out the page, clearing page-dirty.  The
filesystem has no good way to detect that a dirty pte is about to be
attached, so it will happily write out the page, at which point, the
filesystem may manipulate the metadata to reflect that the page is no
longer dirty.

It is not always possible to perform the required metadata manipulation in
->set_page_dirty, because that function cannot block or fail.  The
filesystem may need to allocate some data structure, for example.

And the VM cannot mark the pte dirty before page_mkwrite, because
page_mkwrite is allowed to fail, so we must not allow any window where the
page could be written to if page_mkwrite does fail.

This solution of holding the page locked over the 3 critical operations
(page_mkwrite, setting the pte dirty, and finally setting the page dirty)
closes out races nicely, preventing page cleaning for writeout being
initiated in that window.  This provides the filesystem with a strong
synchronisation against the VM here.

- Sage needs this race closed for ceph filesystem.
- Trond for NFS (http://bugzilla.kernel.org/show_bug.cgi?id=12913).
- I need it for fsblock.
- I suspect other filesystems may need it too (eg. btrfs).
- I have converted buffer.c to the new locking. Even simple block allocation
  under dirty pages might be susceptible to i_size changing under partial page
  at the end of file (we also have a buffer.c-side problem here, but it cannot
  be fixed properly without this patch).
- Other filesystems (eg. NFS, maybe btrfs) will need to change their
  page_mkwrite functions themselves.

[ This also moves page_mkwrite another step closer to fault, which should
  eventually allow page_mkwrite to be moved into ->fault, and thus avoiding a
  filesystem calldown and page lock/unlock cycle in __do_fault. ]

[akpm@linux-foundation.org: fix derefs of NULL ->mapping]
Cc: Sage Weil 
Cc: Trond Myklebust 
Signed-off-by: Nick Piggin 
Cc: Valdis Kletnieks 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: page_mkwrite change prototype to match fault

2009-05-18T23:35:02+00:00

commit c2ec175c39f62949438354f603f4aa170846aabb upstream.

Change the page_mkwrite prototype to take a struct vm_fault, and return
VM_FAULT_xxx flags.  There should be no functional change.

This makes it possible to return much more detailed error information to
the VM (and also can provide more information eg.  virtual_address to the
driver, which might be important in some special cases).

This is required for a subsequent fix.  And will also make it easier to
merge page_mkwrite() with fault() in future.

Signed-off-by: Nick Piggin 
Cc: Chris Mason 
Cc: Trond Myklebust 
Cc: Miklos Szeredi 
Cc: Steven Whitehouse 
Cc: Mark Fasheh 
Cc: Joel Becker 
Cc: Artem Bityutskiy 
Cc: Felix Blyakher 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Bonding: fix zero address hole bug in arp_ip_target list

2009-04-27T17:37:05+00:00

upstream commit: 5a31bec014449dc9ca994e4c1dbf2802b7ca458a

Fix a zero address hole bug in the bonding arp_ip_target list
that was causing the bond to ignore ARP replies (bugz 13006).
Instead of just setting the array entry to zero, we now
copy any additional entries down one slot, putting the
zero entry at the end.  With this change we can now have
all the loops that walk the array stop when they hit a zero
since there will be no addresses after it.

Changes are based in part on code fragment provided in kernel:
bugzilla 13006:

	http://bugzilla.kernel.org/show_bug.cgi?id=13006

by Steve Howard 

Signed-off-by: Brian Haley 
Signed-off-by: Jay Vosburgh 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

trivial: fix orphan dates in ext2 documentation

2009-03-23T21:21:26+00:00

Revert the change to the orphan dates of Windows 95, DOS, compression.
Add a new orphan date for OS/2.

Signed-off-by: Jody McIntyre 
Acked-by: Pavel Machek 
Signed-off-by: Linus Torvalds

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6

2009-03-23T16:25:58+00:00

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (32 commits)
  ucc_geth: Fix oops when using fixed-link support
  dm9000: locking bugfix
  net: update dnet.c for bus_id removal
  dnet: DNET should depend on HAS_IOMEM
  dca: add missing copyright/license headers
  nl80211: Check that function pointer != NULL before using it
  sungem: missing net_device_ops
  be2net: fix to restore vlan ids into BE2 during a IF DOWN->UP cycle
  be2net: replenish when posting to rx-queue is starved in out of mem conditions
  bas_gigaset: correctly allocate USB interrupt transfer buffer
  smsc911x: reset last known duplex and carrier on open
  sh_eth: Fix mistake of the address of SH7763
  sh_eth: Change handling of IRQ
  netns: oops in ip[6]_frag_reasm incrementing stats
  net: kfree(napi->skb) => kfree_skb
  net: fix sctp breakage
  ipv6: fix display of local and remote sit endpoints
  net: Document /proc/sys/net/core/netdev_budget
  tulip: fix crash on iface up with shirq debug
  virtio_net: Make virtio_net support carrier detection
  ...

net: Document /proc/sys/net/core/netdev_budget

2009-03-19T01:51:06+00:00

The NAPI poll parameter netdev_budget is not documented in
kernel-docs. Since it may have a substantial effect on at least some
network loads, it should be.

Signed-off-by: Stanislaw Gruszka  
Signed-off-by: David S. Miller

linux.conf.au 2009: Tuz

2009-03-16T14:55:37+00:00

Impact: help prevent extinction of species

The Tasmanian Devil is a shy iconic Australian creature named for its
spine-chilling screech.  It is threatened with extinction due to a
scientifically interesting but horrific transmissible facial cancer.

This one is standing in for Tux for one release using the far less-known
Devil Facial Tux Disguise.

	Save The Tasmanian Devil http://tassiedevil.com.au

Signed-off-by: Linux.conf.au Hobart Team 
Signed-off-by: Rusty Russell 
Signed-off-by: Linus Torvalds

Merge branch 'hwmon-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6

2009-03-12T23:25:04+00:00

* 'hwmon-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6:
  hwmon: (f75375s) Remove unnecessary and confusing initialization
  hwmon: (it87) Properly decode -128 degrees C temperature
  hwmon: (lm90) Document support for the MAX6648/6692 chips
  hwmon: (abituguru3) Fix I/O error handling

trivial: fix bad links in the ext2 and ext3 documentation

2009-03-12T23:24:25+00:00

Trivial patch to fix bad links in the ext2 and ext3 documentation.

Signed-off-by: Jody McIntyre 
Signed-off-by: Linus Torvalds

hwmon: (lm90) Document support for the MAX6648/6692 chips

2009-03-12T12:36:38+00:00

Update documentation to prevent further confusion/duplication.

Signed-off-by: Darrick J. Wong 
Signed-off-by: Jean Delvare