linux-toradex.git/mm/frontswap.c, branch v3.12-rc1

frontswap: fix incorrect zeroing and allocation size for frontswap_map

2013-06-12T23:29:46+00:00

The bitmap accessed by bitops must have enough size to hold the required
numbers of bits rounded up to a multiple of BITS_PER_LONG.  And the
bitmap must not be zeroed by memset() if the number of bits cleared is
not a multiple of BITS_PER_LONG.

This fixes incorrect zeroing and allocation size for frontswap_map.  The
incorrect zeroing part doesn't cause any problem because frontswap_map
is freed just after zeroing.  But the wrongly calculated allocation size
may cause the problem.

For 32bit systems, the allocation size of frontswap_map is about twice
as large as required size.  For 64bit systems, the allocation size is
smaller than requeired if the number of bits is not a multiple of
BITS_PER_LONG.

Signed-off-by: Akinobu Mita 
Cc: Konrad Rzeszutek Wilk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: get rid of swap_lock dependency

2013-05-01T00:04:00+00:00

Frontswap initialization routine depends on swap_lock, which want to be
atomic about frontswap's first appearance.  IOW, frontswap is not present
and will fail all calls OR frontswap is fully functional but if new
swap_info_struct isn't registered by enable_swap_info, swap subsystem
doesn't start I/O so there is no race between init procedure and page I/O
working on frontswap.

So let's remove unnecessary swap_lock dependency.

Cc: Dan Magenheimer 
Signed-off-by: Minchan Kim 
[v1: Rebased on my branch, reworked to work with backends loading late]
[v2: Added a check for !map]
[v3: Made the invalidate path follow the init path]
[v4: Address comments by Wanpeng Li ]
Signed-off-by: Konrad Rzeszutek Wilk 
Signed-off-by: Bob Liu 
Cc: Wanpeng Li 
Cc: Andor Daam 
Cc: Florian Schmaus 
Cc: Stefan Hengelein 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: frontswap: cleanup code

2013-05-01T00:04:00+00:00

After allowing tmem backends to build/run as modules, frontswap_enabled
always true if defined CONFIG_FRONTSWAP.  But frontswap_test() depends on
whether backend is registered, mv it into frontswap.c using fronstswap_ops
to make the decision.

frontswap_set/clear are not used outside frontswap, so don't export them.

Signed-off-by: Bob Liu 
Cc: Wanpeng Li 
Cc: Andor Daam 
Cc: Dan Magenheimer 
Cc: Florian Schmaus 
Cc: Konrad Rzeszutek Wilk 
Cc: Minchan Kim 
Cc: Stefan Hengelein 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: make frontswap_init use a pointer for the ops

2013-05-01T00:04:00+00:00

This simplifies the code in the frontswap - we can get rid of the
'backend_registered' test and instead check against frontswap_ops.

[v1: Rebase on top of 703ba7fe5e0 (ramster->zcache move]
Signed-off-by: Konrad Rzeszutek Wilk 
Signed-off-by: Bob Liu 
Cc: Wanpeng Li 
Cc: Andor Daam 
Cc: Dan Magenheimer 
Cc: Florian Schmaus 
Cc: Minchan Kim 
Cc: Stefan Hengelein 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: frontswap: lazy initialization to allow tmem backends to build/run as modules

2013-05-01T00:04:00+00:00

With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to
be built/loaded as modules rather than built-in and enabled by a boot
parameter, this patch provides "lazy initialization", allowing backends
to register to frontswap even after swapon was run.  Before a backend
registers all calls to init are recorded and the creation of tmem_pools
delayed until a backend registers or until a frontswap store is
attempted.

Signed-off-by: Stefan Hengelein 
Signed-off-by: Florian Schmaus 
Signed-off-by: Andor Daam 
Signed-off-by: Dan Magenheimer 
[v1: Fixes per Seth Jennings suggestions]
[v2: Removed FRONTSWAP_HAS_.. ]
[v3: Fix up per Bob Liu  recommendations]
[v4: Fix up per Andrew's comments]
Signed-off-by: Konrad Rzeszutek Wilk 
Signed-off-by: Bob Liu 
Cc: Wanpeng Li 
Cc: Dan Magenheimer 
Cc: Minchan Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: support exclusive gets if tmem backend is capable

2012-09-21T14:38:12+00:00

Tmem, as originally specified, assumes that "get" operations
performed on persistent pools never flush the page of data out
of tmem on a successful get, waiting instead for a flush
operation.  This is intended to mimic the model of a swap
disk, where a disk read is non-destructive.  Unlike a
disk, however, freeing up the RAM can be valuable.  Over
the years that frontswap was in the review process, several
reviewers (and notably Hugh Dickins in 2010) pointed out that
this would result, at least temporarily, in two copies of the
data in RAM: one (compressed for zcache) copy in tmem,
and one copy in the swap cache.  We wondered if this could
be done differently, at least optionally.

This patch allows tmem backends to instruct the frontswap
code that this backend performs exclusive gets.  Zcache2
already contains hooks to support this feature.  Other
backends are completely unaffected unless/until they are
updated to support this feature.

While it is not clear that exclusive gets are a performance
win on all workloads at all times, this small patch allows for
experimentation by backends.

P.S. Let's not quibble about the naming of "get" vs "read" vs
"load" etc.  The naming is currently horribly inconsistent between
cleancache and frontswap and existing tmem backends, so will need
to be straightened out as a separate patch.  "Get" is used
by the tmem architecture spec, existing backends, and
all documentation and presentation material so I am
using it in this patch.

Signed-off-by: Dan Magenheimer 
Signed-off-by: Konrad Rzeszutek Wilk

mm: frontswap: fix a wrong if condition in frontswap_shrink

2012-09-21T14:37:45+00:00

pages_to_unuse is set to 0 to unuse all frontswap pages
But that doesn't happen since a wrong condition in frontswap_shrink
cancel it.

-v2: Add comment to explain return value of __frontswap_shrink,
as suggested by Dan Carpenter, thanks

Signed-off-by: Zhenzhong Duan 
Signed-off-by: Konrad Rzeszutek Wilk

mm/frontswap: fix uninit'ed variable warning

2012-08-13T19:41:30+00:00

Fixes uninitialized variable warning on 'type' in frontswap_shrink().
type is set before use by __frontswap_unuse_pages() called by
__frontswap_shrink() called by frontswap_shrink() before use by
try_to_unuse().

Signed-off-by: Seth Jennings 
Signed-off-by: Konrad Rzeszutek Wilk

mm/frontswap: cleanup doc and comment error

2012-07-23T15:16:20+00:00

Signed-off-by: Wanpeng Li 
Signed-off-by: Konrad Rzeszutek Wilk

mm: frontswap: remove unneeded headers

2012-07-23T15:16:13+00:00

Signed-off-by: Sasha Levin 
[v1: Rebased with tracing removed]
Signed-off-by: Konrad Rzeszutek Wilk