23 Dec, 2006
1 commit
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Only (un)account for IO and page-dirtying for devices which have real backing
store (ie: not tmpfs or ramdisks).Cc: "David S. Miller"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 Dec, 2006
2 commits
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truncate presently invalidates the dirty page's buffer_heads then shoots down
the page. But try_to_free_buffers() will now bale out because the page is
dirty.Net effect: the LRU gets filled with dirty pages which have invalidated
buffer_heads attached. They have no ->mapping and hence cannot be cleaned.
The machine leaks memory at an enormous rate.Fix this by cleaning the page before running try_to_free_buffers(), so
try_to_free_buffers() can do its work.Also, remember to do dirty-page-acoounting in cancel_dirty_page() so the
machine won't wedge up trying to write non-existent dirty pages.Probably still wrong, but now less so.
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
They were horribly easy to mis-use because of their tempting naming, and
they also did way more than any users of them generally wanted them to
do.A dirty page can become clean under two circumstances:
(a) when we write it out. We have "clear_page_dirty_for_io()" for
this, and that function remains unchanged.In the "for IO" case it is not sufficient to just clear the dirty
bit, you also have to mark the page as being under writeback etc.(b) when we actually remove a page due to it becoming inaccessible to
users, notably because it was truncate()'d away or the file (or
metadata) no longer exists, and we thus want to cancel any
outstanding dirty state.For the (b) case, we now introduce "cancel_dirty_page()", which only
touches the page state itself, and verifies that the page is not mapped
(since cancelling writes on a mapped page would be actively wrong as it
is still accessible to users).Some filesystems need to be fixed up for this: CIFS, FUSE, JFS,
ReiserFS, XFS all use the old confusing functions, and will be fixed
separately in subsequent commits (with some of them just removing the
offending logic, and others using clear_page_dirty_for_io()).This was confirmed by Martin Michlmayr to fix the apt database
corruption on ARM.Cc: Martin Michlmayr
Cc: Peter Zijlstra
Cc: Hugh Dickins
Cc: Nick Piggin
Cc: Arjan van de Ven
Cc: Andrei Popa
Cc: Andrew Morton
Cc: Dave Kleikamp
Cc: Gordon Farquharson
Cc: Martin Schwidefsky
Cc: Trond Myklebust
Signed-off-by: Linus Torvalds
18 Dec, 2006
1 commit
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fix a typo, sys_mincore() needs min().
Signed-off-by: Oleg Nesterov
Signed-off-by: Linus "I'm a moron" Torvalds
17 Dec, 2006
2 commits
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Hugh Dickins correctly points out that mincore() is actually _supposed_
to fail on an unmapped hole in the user address space, rather than
return valid ("empty") information about the hole. This just simplifies
the problem further (I had been misled by our previous confusing and
complicated way of doing mincore()).Also, in the unlikely situation that we can't allocate a temporary
kernel buffer, we should actually return EAGAIN, not ENOMEM, to keep the
"unmapped hole" and "allocation failure" error cases separate.Finally, add a comment about our stupid historical lack of support for
anonymous mappings. I'll fix that if somebody reminds me after 2.6.20
is out.Acked-by: Hugh Dickins
Signed-off-by: Linus Torvalds -
Doug Chapman noticed that mincore() will doa "copy_to_user()" of the
result while holding the mmap semaphore for reading, which is a big
no-no. While a recursive read-lock on a semaphore in the case of a page
fault happens to work, we don't actually allow them due to deadlock
schenarios with writers due to fairness issues.Doug and Marcel sent in a patch to fix it, but I decided to just rewrite
the mess instead - not just fixing the locking problem, but making the
code smaller and (imho) much easier to understand.Cc: Doug Chapman
Cc: Marcel Holtmann
Cc: Hugh Dickins
Cc: Andrew Morton
Signed-off-by: Linus Torvalds
14 Dec, 2006
6 commits
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To allow a more effective copy_user_highpage() on certain architectures,
a vma argument is added to the function and cow_user_page() allowing
the implementation of these functions to check for the VM_EXEC bit.The main part of this patch was originally written by Ralf Baechle;
Atushi Nemoto did the the debugging.Signed-off-by: Atsushi Nemoto
Signed-off-by: Ralf Baechle
Signed-off-by: Linus Torvalds -
When some objects are allocated by one CPU but freed by another CPU we can
consume lot of cycles doing divides in obj_to_index().(Typical load on a dual processor machine where network interrupts are
handled by one particular CPU (allocating skbufs), and the other CPU is
running the application (consuming and freeing skbufs))Here on one production server (dual-core AMD Opteron 285), I noticed this
divide took 1.20 % of CPU_CLK_UNHALTED events in kernel. But Opteron are
quite modern cpus and the divide is much more expensive on oldest
architectures :On a 200 MHz sparcv9 machine, the division takes 64 cycles instead of 1
cycle for a multiply.Doing some math, we can use a reciprocal multiplication instead of a divide.
If we want to compute V = (A / B) (A and B being u32 quantities)
we can instead use :V = ((u64)A * RECIPROCAL(B)) >> 32 ;
where RECIPROCAL(B) is precalculated to ((1LL << 32) + (B - 1)) / B
Note :
I wrote pure C code for clarity. gcc output for i386 is not optimal but
acceptable :mull 0x14(%ebx)
mov %edx,%eax // part of the >> 32
xor %edx,%edx // useless
mov %eax,(%esp) // could be avoided
mov %edx,0x4(%esp) // useless
mov (%esp),%ebx[akpm@osdl.org: small cleanups]
Signed-off-by: Eric Dumazet
Cc: Christoph Lameter
Cc: David Miller
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Elaborate the API for calling cpuset_zone_allowed(), so that users have to
explicitly choose between the two variants:cpuset_zone_allowed_hardwall()
cpuset_zone_allowed_softwall()Until now, whether or not you got the hardwall flavor depended solely on
whether or not you or'd in the __GFP_HARDWALL gfp flag to the gfp_mask
argument.If you didn't specify __GFP_HARDWALL, you implicitly got the softwall
version.Unfortunately, this meant that users would end up with the softwall version
without thinking about it. Since only the softwall version might sleep,
this led to bugs with possible sleeping in interrupt context on more than
one occassion.The hardwall version requires that the current tasks mems_allowed allows
the node of the specified zone (or that you're in interrupt or that
__GFP_THISNODE is set or that you're on a one cpuset system.)The softwall version, depending on the gfp_mask, might allow a node if it
was allowed in the nearest enclusing cpuset marked mem_exclusive (which
requires taking the cpuset lock 'callback_mutex' to evaluate.)This patch removes the cpuset_zone_allowed() call, and forces the caller to
explicitly choose between the hardwall and the softwall case.If the caller wants the gfp_mask to determine this choice, they should (1)
be sure they can sleep or that __GFP_HARDWALL is set, and (2) invoke the
cpuset_zone_allowed_softwall() routine.This adds another 100 or 200 bytes to the kernel text space, due to the few
lines of nearly duplicate code at the top of both cpuset_zone_allowed_*
routines. It should save a few instructions executed for the calls that
turned into calls of cpuset_zone_allowed_hardwall, thanks to not having to
set (before the call) then check (within the call) the __GFP_HARDWALL flag.For the most critical call, from get_page_from_freelist(), the same
instructions are executed as before -- the old cpuset_zone_allowed()
routine it used to call is the same code as the
cpuset_zone_allowed_softwall() routine that it calls now.Not a perfect win, but seems worth it, to reduce this chance of hitting a
sleeping with irq off complaint again.Signed-off-by: Paul Jackson
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
More cleanups for slab.h
1. Remove tabs from weird locations as suggested by Pekka
2. Drop the check for NUMA and SLAB_DEBUG from the fallback section
as suggested by Pekka.3. Uses static inline for the fallback defs as also suggested by Pekka.
4. Make kmem_ptr_valid take a const * argument.
5. Separate the NUMA fallback definitions from the kmalloc_track fallback
definitions.Signed-off-by: Christoph Lameter
Cc: Pekka Enberg
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This is a response to an earlier discussion on linux-mm about splitting
slab.h components per allocator. Patch is against 2.6.19-git11. See
http://marc.theaimsgroup.com/?l=linux-mm&m=116469577431008&w=2This patch cleans up the slab header definitions. We define the common
functions of slob and slab in slab.h and put the extra definitions needed
for slab's kmalloc implementations in . In order to get
a greater set of common functions we add several empty functions to slob.c
and also rename slob's kmalloc to __kmalloc.Slob does not need any special definitions since we introduce a fallback
case. If there is no need for a slab implementation to provide its own
kmalloc mess^H^H^Hacros then we simply fall back to __kmalloc functions.
That is sufficient for SLOB.Sort the function in slab.h according to their functionality. First the
functions operating on struct kmem_cache * then the kmalloc related
functions followed by special debug and fallback definitions.Also redo a lot of comments.
Signed-off-by: Christoph Lameter ?
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Fallback_alloc() does not do the check for GFP_WAIT as done in
cache_grow(). Thus interrupts are disabled when we call kmem_getpages()
which results in the failure.Duplicate the handling of GFP_WAIT in cache_grow().
Signed-off-by: Christoph Lameter
Cc: Jay Cliburn
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Dec, 2006
7 commits
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This patch introduces users of the round_jiffies() function in the slab code.
The slab code has a few "run every second" timers for background work; these
are obviously not timing critical as long as they happen roughly at the right
frequency.Signed-off-by: Arjan van de Ven
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The only time it is safe to call aio_complete() is when the ->ki_retry
function returns -EIOCBQUEUED to the AIO core. direct_io_worker() has
historically done this by relying on its caller to translate positive return
codes into -EIOCBQUEUED for the aio case. It did this by trying to keep
conditionals in sync. direct_io_worker() knew when finished_one_bio() was
going to call aio_complete(). It would reverse the test and wait and free the
dio in the cases it thought that finished_one_bio() wasn't going to.Not surprisingly, it ended up getting it wrong. 'ret' could be a negative
errno from the submission path but it failed to communicate this to
finished_one_bio(). direct_io_worker() would return < 0, it's callers
wouldn't raise -EIOCBQUEUED, and aio_complete() would be called. In the
future finished_one_bio()'s tests wouldn't reflect this and aio_complete()
would be called for a second time which can manifest as an oops.The previous cleanups have whittled the sync and async completion paths down
to the point where we can collapse them and clearly reassert the invariant
that we must only call aio_complete() after returning -EIOCBQUEUED.
direct_io_worker() will only return -EIOCBQUEUED when it is not the last to
drop the dio refcount and the aio bio completion path will only call
aio_complete() when it is the last to drop the dio refcount.
direct_io_worker() can ensure that it is the last to drop the reference count
by waiting for bios to drain. It does this for sync ops, of course, and for
partial dio writes that must fall back to buffered and for aio ops that saw
errors during submission.This means that operations that end up waiting, even if they were issued as
aio ops, will not call aio_complete() from dio. Instead we return the return
code of the operation and let the aio core call aio_complete(). This is
purposely done to fix a bug where AIO DIO file extensions would call
aio_complete() before their callers have a chance to update i_size.Now that direct_io_worker() is explicitly returning -EIOCBQUEUED its callers
no longer have to translate for it. XFS needs to be careful not to free
resources that will be used during AIO completion if -EIOCBQUEUED is returned.
We maintain the previous behaviour of trying to write fs metadata for O_SYNC
aio+dio writes.Signed-off-by: Zach Brown
Cc: Badari Pulavarty
Cc: Suparna Bhattacharya
Acked-by: Jeff Moyer
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
nfs's ->readpages uses read_cache_pages(). Wire it up there.
[wfg@mail.ustc.edu.cn: account only successful nfs/fuse reads]
Cc: Jay Lan
Cc: Shailabh Nagar
Cc: Balbir Singh
Cc: Chris Sturtivant
Cc: Tony Ernst
Cc: Guillaume Thouvenin
Cc: David Wright
Signed-off-by: Fengguang Wu
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Account for the number of byte writes which this process caused to not happen
after all.Cc: Jay Lan
Cc: Shailabh Nagar
Cc: Balbir Singh
Cc: Chris Sturtivant
Cc: Tony Ernst
Cc: Guillaume Thouvenin
Cc: David Wright
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Accounting writes is fairly simple: whenever a process flips a page from clean
to dirty, we accuse it of having caused a write to underlying storage of
PAGE_CACHE_SIZE bytes.This may overestimate the amount of writing: the page-dirtying may cause only
one buffer_head's worth of writeout. Fixing that is possible, but probably a
bit messy and isn't obviously important.Cc: Jay Lan
Cc: Shailabh Nagar
Cc: Balbir Singh
Cc: Chris Sturtivant
Cc: Tony Ernst
Cc: Guillaume Thouvenin
Cc: David Wright
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Save a tabstop in __set_page_dirty_nobuffers() and __set_page_dirty_buffers()
and a few other places. No functional changes.Cc: Jay Lan
Cc: Shailabh Nagar
Cc: Balbir Singh
Cc: Chris Sturtivant
Cc: Tony Ernst
Cc: Guillaume Thouvenin
Cc: David Wright
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Ramiro Voicu hits the BUG_ON(!pte_none(*pte)) in zeromap_pte_range: kernel
bugzilla 7645. Right: read_zero_pagealigned uses down_read of mmap_sem,
but another thread's racing read of /dev/zero, or a normal fault, can
easily set that pte again, in between zap_page_range and zeromap_page_range
getting there. It's been wrong ever since 2.4.3.The simple fix is to use down_write instead, but that would serialize reads
of /dev/zero more than at present: perhaps some app would be badly
affected. So instead let zeromap_page_range return the error instead of
BUG_ON, and read_zero_pagealigned break to the slower clear_user loop in
that case - there's no need to optimize for it.Use -EEXIST for when a pte is found: BUG_ON in mmap_zero (the other user of
zeromap_page_range), though it really isn't interesting there. And since
mmap_zero wants -EAGAIN for out-of-memory, the zeromaps better return that
than -ENOMEM.Signed-off-by: Hugh Dickins
Cc: Ramiro Voicu:
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 Dec, 2006
7 commits
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Assign defaults most likely to please a new user:
1) generate some logging output
(verbose=2)
2) avoid injecting failures likely to lock up UI
(ignore_gfp_wait=1, ignore_gfp_highmem=1)Signed-off-by: Don Mullis
Cc: Akinobu Mita
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch provides fault-injection capability for alloc_pages()
Boot option:
fail_page_alloc=,,,
-- specifies the interval of failures.
-- specifies how often it should fail in percent.
-- specifies the size of free space where memory can be
allocated safely in pages.-- specifies how many times failures may happen at most.
Debugfs:
/debug/fail_page_alloc/interval
/debug/fail_page_alloc/probability
/debug/fail_page_alloc/specifies
/debug/fail_page_alloc/times
/debug/fail_page_alloc/ignore-gfp-highmem
/debug/fail_page_alloc/ignore-gfp-waitExample:
fail_page_alloc=10,100,0,-1
The page allocation (alloc_pages(), ...) fails once per 10 times.
Signed-off-by: Akinobu Mita
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch provides fault-injection capability for kmalloc.
Boot option:
failslab=,,,
-- specifies the interval of failures.
-- specifies how often it should fail in percent.
-- specifies the size of free space where memory can be
allocated safely in bytes.-- specifies how many times failures may happen at most.
Debugfs:
/debug/failslab/interval
/debug/failslab/probability
/debug/failslab/specifies
/debug/failslab/times
/debug/failslab/ignore-gfp-highmem
/debug/failslab/ignore-gfp-waitExample:
failslab=10,100,0,-1
slab allocation (kmalloc(), kmem_cache_alloc(),..) fails once per 10 times.
Cc: Pekka Enberg
Signed-off-by: Akinobu Mita
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This facility provides three entry points:
ilog2() Log base 2 of unsigned long
ilog2_u32() Log base 2 of u32
ilog2_u64() Log base 2 of u64These facilities can either be used inside functions on dynamic data:
int do_something(long q)
{
...;
y = ilog2(x)
...;
}Or can be used to statically initialise global variables with constant values:
unsigned n = ilog2(27);
When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant. They treat negative numbers as
unsigned.When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.[akpm@osdl.org: MMC fix]
Signed-off-by: David Howells
Cc: Benjamin Herrenschmidt
Cc: Paul Mackerras
Cc: Herbert Xu
Cc: David Howells
Cc: Wojtek Kaniewski
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Josef Sipek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Change all the uses of f_{dentry,vfsmnt} to f_path.{dentry,mnt} in linux/mm/.
Signed-off-by: Josef "Jeff" Sipek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
fallback_alloc() could end up calling cpuset_zone_allowed() with interrupts
disabled (by code in kmem_cache_alloc_node()), but without __GFP_HARDWALL
set, leading to a possible call of a sleeping function with interrupts
disabled.This results in the BUG report:
BUG: sleeping function called from invalid context at kernel/cpuset.c:1520
in_atomic():0, irqs_disabled():1Thanks to Paul Menage for catching this one.
Signed-off-by: Paul Jackson
Cc: Paul Menage
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Dec, 2006
14 commits
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- move some file_operations structs into the .rodata section
- move static strings from policy_types[] array into the .rodata section
- fix generic seq_operations usages, so that those structs may be defined
as "const" as well[akpm@osdl.org: couple of fixes]
Signed-off-by: Helge Deller
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In time for 2.6.20, we can get rid of this junk.
Signed-off-by: Adrian Bunk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Adrian Bunk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There was lots of #ifdef noise in the kernel due to hotcpu_notifier(fn,
prio) not correctly marking 'fn' as used in the !HOTPLUG_CPU case, and thus
generating compiler warnings of unused symbols, hence forcing people to add
#ifdefs.the compiler can skip truly unused functions just fine:
text data bss dec hex filename
1624412 728710 3674856 6027978 5bfaca vmlinux.before
1624412 728710 3674856 6027978 5bfaca vmlinux.after[akpm@osdl.org: topology.c fix]
Signed-off-by: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
It has no users and it's doubtful that we'll need it again.
Cc: "David S. Miller"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Use put_pages_list() instead of opencoding it.
Signed-off-by: OGAWA Hirofumi
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Move process freezing functions from include/linux/sched.h to freezer.h, so
that modifications to the freezer or the kernel configuration don't require
recompiling just about everything.[akpm@osdl.org: fix ueagle driver]
Signed-off-by: Nigel Cunningham
Cc: "Rafael J. Wysocki"
Cc: Pavel Machek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Currently swsusp saves the contents of highmem pages by copying them to the
normal zone which is quite inefficient (eg. it requires two normal pages
to be used for saving one highmem page). This may be improved by using
highmem for saving the contents of saveable highmem pages.Namely, during the suspend phase of the suspend-resume cycle we try to
allocate as many free highmem pages as there are saveable highmem pages.
If there are not enough highmem image pages to store the contents of all of
the saveable highmem pages, some of them will be stored in the "normal"
memory. Next, we allocate as many free "normal" pages as needed to store
the (remaining) image data. We use a memory bitmap to mark the allocated
free pages (ie. highmem as well as "normal" image pages).Now, we use another memory bitmap to mark all of the saveable pages
(highmem as well as "normal") and the contents of the saveable pages are
copied into the image pages. Then, the second bitmap is used to save the
pfns corresponding to the saveable pages and the first one is used to save
their data.During the resume phase the pfns of the pages that were saveable during the
suspend are loaded from the image and used to mark the "unsafe" page
frames. Next, we try to allocate as many free highmem page frames as to
load all of the image data that had been in the highmem before the suspend
and we allocate so many free "normal" page frames that the total number of
allocated free pages (highmem and "normal") is equal to the size of the
image. While doing this we have to make sure that there will be some extra
free "normal" and "safe" page frames for two lists of PBEs constructed
later.Now, the image data are loaded, if possible, into their "original" page
frames. The image data that cannot be written into their "original" page
frames are loaded into "safe" page frames and their "original" kernel
virtual addresses, as well as the addresses of the "safe" pages containing
their copies, are stored in one of two lists of PBEs.One list of PBEs is for the copies of "normal" suspend pages (ie. "normal"
pages that were saveable during the suspend) and it is used in the same way
as previously (ie. by the architecture-dependent parts of swsusp). The
other list of PBEs is for the copies of highmem suspend pages. The pages
in this list are restored (in a reversible way) right before the
arch-dependent code is called.Signed-off-by: Rafael J. Wysocki
Cc: Pavel Machek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Make swsusp use block device offsets instead of swap offsets to identify swap
locations and make it use the same code paths for writing as well as for
reading data.This allows us to use the same code for handling swap files and swap
partitions and to simplify the code, eg. by dropping rw_swap_page_sync().Signed-off-by: Rafael J. Wysocki
Cc: Pavel Machek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The Linux kernel handles swap files almost in the same way as it handles swap
partitions and there are only two differences between these two types of swap
areas:(1) swap files need not be contiguous,
(2) the header of a swap file is not in the first block of the partition
that holds it. From the swsusp's point of view (1) is not a problem,
because it is already taken care of by the swap-handling code, but (2) has
to be taken into consideration.In principle the location of a swap file's header may be determined with the
help of appropriate filesystem driver. Unfortunately, however, it requires
the filesystem holding the swap file to be mounted, and if this filesystem is
journaled, it cannot be mounted during a resume from disk. For this reason we
need some other means by which swap areas can be identified.For example, to identify a swap area we can use the partition that holds the
area and the offset from the beginning of this partition at which the swap
header is located.The following patch allows swsusp to identify swap areas this way. It changes
swap_type_of() so that it takes an additional argument representing an offset
of the swap header within the partition represented by its first argument.Signed-off-by: Rafael J. Wysocki
Acked-by: Pavel Machek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Make radix tree lookups safe to be performed without locks. Readers are
protected against nodes being deleted by using RCU based freeing. Readers
are protected against new node insertion by using memory barriers to ensure
the node itself will be properly written before it is visible in the radix
tree.Each radix tree node keeps a record of their height (above leaf nodes).
This height does not change after insertion -- when the radix tree is
extended, higher nodes are only inserted in the top. So a lookup can take
the pointer to what is *now* the root node, and traverse down it even if
the tree is concurrently extended and this node becomes a subtree of a new
root."Direct" pointers (tree height of 0, where root->rnode points directly to
the data item) are handled by using the low bit of the pointer to signal
whether rnode is a direct pointer or a pointer to a radix tree node.When a reader wants to traverse the next branch, they will take a copy of
the pointer. This pointer will be either NULL (and the branch is empty) or
non-NULL (and will point to a valid node).[akpm@osdl.org: cleanups]
[Lee.Schermerhorn@hp.com: bugfixes, comments, simplifications]
[clameter@sgi.com: build fix]
Signed-off-by: Nick Piggin
Cc: "Paul E. McKenney"
Signed-off-by: Lee Schermerhorn
Cc: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Currently we we use the lru head link of the second page of a compound page
to hold its destructor. This was ok when it was purely an internal
implmentation detail. However, hugetlbfs overrides this destructor
violating the layering. Abstract this out as explicit calls, also
introduce a type for the callback function allowing them to be type
checked. For each callback we pre-declare the function, causing a type
error on definition rather than on use elsewhere.[akpm@osdl.org: cleanups]
Signed-off-by: Andy Whitcroft
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
