01 Oct, 2013
1 commit
-
madvise_hwpoison won't check if the page is small page or huge page and
traverses in small page granularity against the range unconditionally,
which result in a printk flood "MCE xxx: already hardware poisoned" if
the page is a huge page.This patch fixes it by using compound_order(compound_head(page)) for
huge page iterator.Testcase:
#define _GNU_SOURCE
#include
#include
#include
#include
#include
#include
#include#define PAGES_TO_TEST 3
#define PAGE_SIZE 4096 * 512int main(void)
{
char *mem;
int i;mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, 0, 0);if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
return -1;munmap(mem, PAGES_TO_TEST * PAGE_SIZE);
return 0;
}Signed-off-by: Wanpeng Li
Reviewed-by: Naoya Horiguchi
Acked-by: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
12 Sep, 2013
5 commits
-
madvise_hwpoison() has two locals called "ret". Fix it all up.
Cc: Wanpeng Li
Cc: Naoya Horiguchi
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The return value outside for loop is always zero which means
madvise_hwpoison return success, however, this is not truth for
soft_offline_page w/ failure return value.Signed-off-by: Wanpeng Li
Reviewed-by: Naoya Horiguchi
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
madvise hwpoison inject will poison the read-only empty zero page if there
is no write access before poison. Empty zero page reference count will be
increased for hwpoison, subsequent poison zero page will return directly
since page has already been set PG_hwpoison, however, page reference count
is still increased by get_user_pages_fast. The unpoison process will
unpoison the empty zero page and decrease the reference count successfully
for the fist time, however, subsequent unpoison empty zero page will
return directly since page has already been unpoisoned and without
decrease the page reference count of empty zero page.This patch fixes it by make madvise_hwpoison() put a page and return
immediately (without calling memory_failure() or soft_offline_page()) when
the page is already hwpoisoned.Testcase:
#define _GNU_SOURCE
#include
#include
#include
#include
#include
#include
#include#define PAGES_TO_TEST 3
#define PAGE_SIZE 4096int main(void)
{
char *mem;
int i;mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
return -1;munmap(mem, PAGES_TO_TEST * PAGE_SIZE);
return 0;
}Add printk to dump page reference count:
[ 93.075959] Injecting memory failure for page 0x19d0 at 0xb77d8000
[ 93.076207] MCE 0x19d0: non LRU page recovery: Ignored
[ 93.076209] pfn 0x19d0, page count = 1 after memory failure
[ 93.076220] Injecting memory failure for page 0x19d0 at 0xb77d9000
[ 93.076221] MCE 0x19d0: already hardware poisoned
[ 93.076222] pfn 0x19d0, page count = 2 after memory failure
[ 93.076224] Injecting memory failure for page 0x19d0 at 0xb77da000
[ 93.076224] MCE 0x19d0: already hardware poisoned
[ 93.076225] pfn 0x19d0, page count = 3 after memory failureSigned-off-by: Wanpeng Li
Suggested-by: Naoya Horiguchi
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add '#' to madvise_hwpoison.
Before patch:
[ 95.892866] Injecting memory failure for page 19d0 at b7786000
[ 95.893151] MCE 0x19d0: non LRU page recovery: IgnoredAfter patch:
[ 95.892866] Injecting memory failure for page 0x19d0 at 0xb7786000
[ 95.893151] MCE 0x19d0: non LRU page recovery: IgnoredSigned-off-by: Wanpeng Li
Reviewed-by: Naoya Horiguchi
Cc: Andi Kleen
Cc: Tony Luck
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This fixes following errors:
- ERROR: "(foo*)" should be "(foo *)"
- ERROR: "foo ** bar" should be "foo **bar"Signed-off-by: Vladimir Cernov
Reviewed-by: Pekka Enberg
Acked-by: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Apr, 2013
1 commit
-
In madvise(), there doesn't seem to be any reason for taking the
¤t->mm->mmap_sem before start and len_in have been validated.
Incidentally, this removes the need for the out: label.[akpm@linux-foundation.org: s/out_plug/out/, per David]
Signed-off-by: Rasmus Villemoes
Acked-by: KOSAKI Motohiro
Acked-by: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
24 Feb, 2013
1 commit
-
Make madvise(MADV_WILLNEED) support swap file prefetch. If memory is
swapout, this syscall can do swapin prefetch. It has no impact if the
memory isn't swapout.[akpm@linux-foundation.org: fix CONFIG_SWAP=n build]
[sasha.levin@oracle.com: fix BUG on madvise early failure]
Signed-off-by: Shaohua Li
Cc: Hugh Dickins
Cc: Rik van Riel
Signed-off-by: Sasha Levin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 Oct, 2012
1 commit
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Rename VM_NODUMP into VM_DONTDUMP: this name matches other negative flags:
VM_DONTEXPAND, VM_DONTCOPY. Currently this flag used only for
sys_madvise. The next patch will use it for replacing the outdated flag
VM_RESERVED.Also forbid madvise(MADV_DODUMP) for special kernel mappings VM_SPECIAL
(VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)Signed-off-by: Konstantin Khlebnikov
Cc: Alexander Viro
Cc: Carsten Otte
Cc: Chris Metcalf
Cc: Cyrill Gorcunov
Cc: Eric Paris
Cc: H. Peter Anvin
Cc: Hugh Dickins
Cc: Ingo Molnar
Cc: James Morris
Cc: Jason Baron
Cc: Kentaro Takeda
Cc: Matt Helsley
Cc: Nick Piggin
Cc: Oleg Nesterov
Cc: Peter Zijlstra
Cc: Robert Richter
Cc: Suresh Siddha
Cc: Tetsuo Handa
Cc: Venkatesh Pallipadi
Acked-by: Linus Torvalds
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Jul, 2012
1 commit
-
Otherwise the code races with munmap (causing a use-after-free
of the vma) or with close (causing a use-after-free of the struct
file).The bug was introduced by commit 90ed52ebe481 ("[PATCH] holepunch: fix
mmap_sem i_mutex deadlock")Cc: Hugh Dickins
Cc: Miklos Szeredi
Cc: Badari Pulavarty
Cc: Nick Piggin
Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski
Signed-off-by: Linus Torvalds
30 May, 2012
1 commit
-
Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
to use do_fallocate() instead of vmtruncate_range(): which extends
madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.There is one more user of vmtruncate_range() in our tree,
staging/android's ashmem_shrink(): convert it to use do_fallocate() too
(but if its unpinned areas are already unmapped - I don't know - then it
would do better to use shmem_truncate_range() directly).Based-on-patch-by: Cong Wang
Signed-off-by: Hugh Dickins
Cc: Christoph Hellwig
Cc: Al Viro
Cc: Colin Cross
Cc: John Stultz
Cc: Greg Kroah-Hartman
Cc: "Theodore Ts'o"
Cc: Andreas Dilger
Cc: Mark Fasheh
Cc: Joel Becker
Cc: Dave Chinner
Cc: Ben Myers
Cc: Michael Kerrisk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
24 Mar, 2012
1 commit
-
Since we no longer need the VM_ALWAYSDUMP flag, let's use the freed bit
for 'VM_NODUMP' flag. The idea is is to add a new madvise() flag:
MADV_DONTDUMP, which can be set by applications to specifically request
memory regions which should not dump core.The specific application I have in mind is qemu: we can add a flag there
that wouldn't dump all of guest memory when qemu dumps core. This flag
might also be useful for security sensitive apps that want to absolutely
make sure that parts of memory are not dumped. To clear the flag use:
MADV_DODUMP.[akpm@linux-foundation.org: s/MADV_NODUMP/MADV_DONTDUMP/, s/MADV_CLEAR_NODUMP/MADV_DODUMP/, per Roland]
[akpm@linux-foundation.org: fix up the architectures which broke]
Signed-off-by: Jason Baron
Acked-by: Roland McGrath
Cc: Chris Metcalf
Cc: Avi Kivity
Cc: Ralf Baechle
Cc: Richard Henderson
Cc: Ivan Kokshaysky
Cc: Matt Turner
Cc: "James E.J. Bottomley"
Cc: Helge Deller
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
04 Jan, 2012
1 commit
-
There is only one caller of memory_failure(), all other users call
__memory_failure() and pass in the flags argument explicitly. The
lone user of memory_failure() will soon need to pass flags too.Add flags argument to the callsite in mce.c. Delete the old memory_failure()
function, and then rename __memory_failure() without the leading "__".Provide clearer message when action optional memory errors are ignored.
Acked-by: Borislav Petkov
Signed-off-by: Tony Luck
21 Jul, 2011
1 commit
-
i_alloc_sem is a rather special rw_semaphore. It's the last one that may
be released by a non-owner, and it's write side is always mirrored by
real exclusion. It's intended use it to wait for all pending direct I/O
requests to finish before starting a truncate.Replace it with a hand-grown construct:
- exclusion for truncates is already guaranteed by i_mutex, so it can
simply fall way
- the reader side is replaced by an i_dio_count member in struct inode
that counts the number of pending direct I/O requests. Truncate can't
proceed as long as it's non-zero
- when i_dio_count reaches non-zero we wake up a pending truncate using
wake_up_bit on a new bit in i_flags
- new references to i_dio_count can't appear while we are waiting for
it to read zero because the direct I/O count always needs i_mutex
(or an equivalent like XFS's i_iolock) for starting a new operation.This scheme is much simpler, and saves the space of a spinlock_t and a
struct list_head in struct inode (typically 160 bits on a non-debug 64-bit
system).Signed-off-by: Christoph Hellwig
Signed-off-by: Al Viro
14 Jan, 2011
3 commits
-
MADV_HUGEPAGE and MADV_NOHUGEPAGE were fully effective only if run after
mmap and before touching the memory. While this is enough for most
usages, it's little effort to make madvise more dynamic at runtime on an
existing mapping by making khugepaged aware about madvise.MADV_HUGEPAGE: register in khugepaged immediately without waiting a page
fault (that may not ever happen if all pages are already mapped and the
"enabled" knob was set to madvise during the initial page faults).MADV_NOHUGEPAGE: skip vmas marked VM_NOHUGEPAGE in khugepaged to stop
collapsing pages where not needed.[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Andrea Arcangeli
Cc: Michael Kerrisk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add madvise MADV_NOHUGEPAGE to mark regions that are not important to be
hugepage backed. Return -EINVAL if the vma is not of an anonymous type,
or the feature isn't built into the kernel. Never silently return
success.Signed-off-by: Andrea Arcangeli
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add madvise MADV_HUGEPAGE to mark regions that are important to be
hugepage backed. Return -EINVAL if the vma is not of an anonymous type,
or the feature isn't built into the kernel. Never silently return
success.Signed-off-by: Andrea Arcangeli
Acked-by: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Dec, 2009
4 commits
-
Process based injection is much easier to handle for test programs,
who can first bring a page into a specific state and then test.
So add a new MADV_SOFT_OFFLINE to soft offline a page, similar
to the existing hard offline injector.Signed-off-by: Andi Kleen
-
The previous version didn't take the mmap_sem before calling gup(),
which is racy.Use get_user_pages_fast() instead which doesn't need any locks.
This is also faster of course, but then it doesn't really matter
because this is just a testing path.Based on report from Nick Piggin.
Cc: npiggin@suse.deSigned-off-by: Andi Kleen
-
Now that "ref" is just a boolean turn it into
a flags argument. First step is only a single flag
that makes the code's intention more clear, but more
may follow.Signed-off-by: Andi Kleen
-
If page is double referenced in madvise_hwpoison() and __memory_failure(),
remove_mapping() will fail because it expects page_count=2. Fix it by
not grabbing extra page count in __memory_failure().Signed-off-by: Wu Fengguang
Signed-off-by: Andi Kleen
24 Sep, 2009
1 commit
-
* 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6: (21 commits)
HWPOISON: Enable error_remove_page on btrfs
HWPOISON: Add simple debugfs interface to inject hwpoison on arbitary PFNs
HWPOISON: Add madvise() based injector for hardware poisoned pages v4
HWPOISON: Enable error_remove_page for NFS
HWPOISON: Enable .remove_error_page for migration aware file systems
HWPOISON: The high level memory error handler in the VM v7
HWPOISON: Add PR_MCE_KILL prctl to control early kill behaviour per process
HWPOISON: shmem: call set_page_dirty() with locked page
HWPOISON: Define a new error_remove_page address space op for async truncation
HWPOISON: Add invalidate_inode_page
HWPOISON: Refactor truncate to allow direct truncating of page v2
HWPOISON: check and isolate corrupted free pages v2
HWPOISON: Handle hardware poisoned pages in try_to_unmap
HWPOISON: Use bitmask/action code for try_to_unmap behaviour
HWPOISON: x86: Add VM_FAULT_HWPOISON handling to x86 page fault handler v2
HWPOISON: Add poison check to page fault handling
HWPOISON: Add basic support for poisoned pages in fault handler v3
HWPOISON: Add new SIGBUS error codes for hardware poison signals
HWPOISON: Add support for poison swap entries v2
HWPOISON: Export some rmap vma locking to outside world
...
22 Sep, 2009
2 commits
-
This patch presents the mm interface to a dummy version of ksm.c, for
better scrutiny of that interface: the real ksm.c follows later.When CONFIG_KSM is not set, madvise(2) reject MADV_MERGEABLE and
MADV_UNMERGEABLE with EINVAL, since that seems more helpful than
pretending that they can be serviced. But when CONFIG_KSM=y, accept them
even if KSM is not currently running, and even on areas which KSM will not
touch (e.g. hugetlb or shared file or special driver mappings).Like other madvices, report ENOMEM despite success if any area in the
range is unmapped, and use EAGAIN to report out of memory.Define vma flag VM_MERGEABLE to identify an area on which KSM may try
merging pages: leave it to ksm_madvise() to decide whether to set it.
Define mm flag MMF_VM_MERGEABLE to identify an mm which might contain
VM_MERGEABLE areas, to minimize callouts when forking or exiting.Based upon earlier patches by Chris Wright and Izik Eidus.
Signed-off-by: Hugh Dickins
Signed-off-by: Chris Wright
Signed-off-by: Izik Eidus
Cc: Michael Kerrisk
Cc: Andrea Arcangeli
Cc: Rik van Riel
Cc: Wu Fengguang
Cc: Balbir Singh
Cc: Hugh Dickins
Cc: KAMEZAWA Hiroyuki
Cc: Lee Schermerhorn
Cc: Avi Kivity
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
madvise.c has several levels of switch statements, what to do in which?
Move MADV_DOFORK code down from madvise_vma() to madvise_behavior(), so
madvise_vma() can be a simple router, to madvise_behavior() by default.vma->vm_flags is an unsigned long so use the same type for new_flags. Add
missing comment lines to describe MADV_DONTFORK and MADV_DOFORK.Signed-off-by: Hugh Dickins
Signed-off-by: Chris Wright
Signed-off-by: Izik Eidus
Cc: Andrea Arcangeli
Cc: Rik van Riel
Cc: Wu Fengguang
Cc: Balbir Singh
Cc: Hugh Dickins
Cc: KAMEZAWA Hiroyuki
Cc: Lee Schermerhorn
Cc: Avi Kivity
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Sep, 2009
1 commit
-
Impact: optional, useful for debugging
Add a new madvice sub command to inject poison for some
pages in a process' address space. This is useful for
testing the poison page handling.This patch can allow root to tie up large amounts of memory.
I got feedback from container developers and they didn't see any
problem.v2: Use write flag for get_user_pages to make sure to always get
a fresh page
v3: Don't request write mapping (Fengguang Wu)
v4: Move MADV_* number to avoid conflict with KSM (Hugh Dickins)Signed-off-by: Andi Kleen
17 Jun, 2009
2 commits
-
The posix_madvise() function succeeds (and does nothing) when called with
parameters (NULL, 0, -1); according to LSB tests, it should fail with
EINVAL because -1 is not a valid flag.When called with a valid address and size, it correctly fails.
So perform an initial check for valid flags first.
Reported-by: Jiri Dluhos
Signed-off-by: Nick Piggin
Reviewed-and-Tested-by: WANG Cong
Cc: Michael Kerrisk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Impact: code simplification.
Cc: Nick Piggin
Signed-off-by: Wu Fengguang
Cc: Ying Han
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 May, 2009
1 commit
-
This reverts commit a425a638c858fd10370b573bde81df3ba500e271.
Now that the previous commit removed the "readpage" actor for hugetlb
files, read-ahead will no longer mess up the mapping, and there's no
longer any reason to treat hugetlbfs mappings specially.Tested-and-acked-by: Mel Gorman
Signed-off-by: Linus Torvalds
06 May, 2009
1 commit
-
madvise(MADV_WILLNEED) forces page cache readahead on a range of memory
backed by a file. The assumption is made that the page required is
order-0 and "normal" page cache.On hugetlbfs, this assumption is not true and order-0 pages are
allocated and inserted into the hugetlbfs page cache. This leaks
hugetlbfs page reservations and can cause BUGs to trigger related to
corrupted page tables.This patch causes MADV_WILLNEED to be ignored for hugetlbfs-backed
regions.Signed-off-by: Mel Gorman
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds
14 Jan, 2009
1 commit
-
Signed-off-by: Heiko Carstens
31 Jul, 2008
1 commit
-
Signed-off-by: Fernando Luis Vazquez Cao
Cc: Hugh Dickins
Cc: Nick Piggin
Cc: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
28 Apr, 2008
1 commit
-
Convert XIP to support non-struct page backed memory, using VM_MIXEDMAP for
the user mappings.This requires the get_xip_page API to be changed to an address based one.
Improve the API layering a little bit too, while we're here.This is required in order to support XIP filesystems on memory that isn't
backed with struct page (but memory with struct page is still supported too).Signed-off-by: Nick Piggin
Acked-by: Carsten Otte
Cc: Jared Hulbert
Cc: Martin Schwidefsky
Cc: Heiko Carstens
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Jul, 2007
1 commit
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In the new madvise_need_mmap_write() call we can avoid an extra case
statement and function call as follows.Signed-off-by: Jason Baron
Cc: Nishanth Aravamudan
Cc: Christoph Hellwig
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 May, 2007
1 commit
-
First thing mm.h does is including sched.h solely for can_do_mlock() inline
function which has "current" dereference inside. By dealing with can_do_mlock()
mm.h can be detached from sched.h which is good. See below, why.This patch
a) removes unconditional inclusion of sched.h from mm.h
b) makes can_do_mlock() normal function in mm/mlock.c
c) exports can_do_mlock() to not break compilation
d) adds sched.h inclusions back to files that were getting it indirectly.
e) adds less bloated headers to some files (asm/signal.h, jiffies.h) that were
getting them indirectlyNet result is:
a) mm.h users would get less code to open, read, preprocess, parse, ... if
they don't need sched.h
b) sched.h stops being dependency for significant number of files:
on x86_64 allmodconfig touching sched.h results in recompile of 4083 files,
after patch it's only 3744 (-8.3%).Cross-compile tested on
all arm defconfigs, all mips defconfigs, all powerpc defconfigs,
alpha alpha-up
arm
i386 i386-up i386-defconfig i386-allnoconfig
ia64 ia64-up
m68k
mips
parisc parisc-up
powerpc powerpc-up
s390 s390-up
sparc sparc-up
sparc64 sparc64-up
um-x86_64
x86_64 x86_64-up x86_64-defconfig x86_64-allnoconfigas well as my two usual configs.
Signed-off-by: Alexey Dobriyan
Signed-off-by: Linus Torvalds
08 May, 2007
1 commit
-
Avoid down_write of the mmap_sem in madvise when we can help it.
Acked-by: Hugh Dickins
Signed-off-by: Nick Piggin
Cc: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Mar, 2007
1 commit
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sys_madvise has down_write of mmap_sem, then madvise_remove calls
vmtruncate_range which takes i_mutex and i_alloc_sem: no, we can easily devise
deadlocks from that ordering.madvise_remove drop mmap_sem while calling vmtruncate_range: luckily, since
madvise_remove doesn't split or merge vmas, it's easy to handle this case with
a NULL prev, without restructuring sys_madvise. (Though sad to retake
mmap_sem when it's unlikely to be needed, and certainly down_read is
sufficient for MADV_REMOVE, unlike the other madvices.)Signed-off-by: Hugh Dickins
Cc: Miklos Szeredi
Cc: Badari Pulavarty
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Mar, 2007
1 commit
-
madvise(MADV_REMOVE) can go into an infinite loop or cause an oops if the
call covers a region from the start of a vma, and extending past that vma.Signed-off-by: Nick Piggin
Cc: Badari Pulavarty
Acked-by: Hugh Dickins
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Apr, 2006
1 commit
-
madvise_remove needs to respect file and mmap protections.
Signed-off-by: Hugh Dickins
[ Will the real CVE-2006-1524 stand up, please.. ]
Signed-off-by: Linus Torvalds
15 Feb, 2006
1 commit
-
Currently, copy-on-write may change the physical address of a page even if the
user requested that the page is pinned in memory (either by mlock or by
get_user_pages). This happens if the process forks meanwhile, and the parent
writes to that page. As a result, the page is orphaned: in case of
get_user_pages, the application will never see any data hardware DMA's into
this page after the COW. In case of mlock'd memory, the parent is not getting
the realtime/security benefits of mlock.In particular, this affects the Infiniband modules which do DMA from and into
user pages all the time.This patch adds madvise options to control whether memory range is inherited
across fork. Useful e.g. for when hardware is doing DMA from/into these
pages. Could also be useful to an application wanting to speed up its forks
by cutting large areas out of consideration.Signed-off-by: Michael S. Tsirkin
Acked-by: Hugh Dickins
Cc: Michael Kerrisk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Jan, 2006
1 commit
-
Here is the patch to implement madvise(MADV_REMOVE) - which frees up a
given range of pages & its associated backing store. Current
implementation supports only shmfs/tmpfs and other filesystems return
-ENOSYS."Some app allocates large tmpfs files, then when some task quits and some
client disconnect, some memory can be released. However the only way to
release tmpfs-swap is to MADV_REMOVE". - Andrea ArcangeliDatabases want to use this feature to drop a section of their bufferpool
(shared memory segments) - without writing back to disk/swap space.This feature is also useful for supporting hot-plug memory on UML.
Concerns raised by Andrew Morton:
- "We have no plan for holepunching! If we _do_ have such a plan (or
might in the future) then what would the API look like? I think
sys_holepunch(fd, start, len), so we should start out with that."- Using madvise is very weird, because people will ask "why do I need to
mmap my file before I can stick a hole in it?"- None of the other madvise operations call into the filesystem in this
manner. A broad question is: is this capability an MM operation or a
filesytem operation? truncate, for example, is a filesystem operation
which sometimes has MM side-effects. madvise is an mm operation and with
this patch, it gains FS side-effects, only they're really, really
significant ones."Comments:
- Andrea suggested the fs operation too but then it's more efficient to
have it as a mm operation with fs side effects, because they don't
immediatly know fd and physical offset of the range. It's possible to
fixup in userland and to use the fs operation but it's more expensive,
the vmas are already in the kernel and we can use them.Short term plan & Future Direction:
- We seem to need this interface only for shmfs/tmpfs files in the short
term. We have to add hooks into the filesystem for correctness and
completeness. This is what this patch does.- In the future, plan is to support both fs and mmap apis also. This
also involves (other) filesystem specific functions to be implemented.- Current patch doesn't support VM_NONLINEAR - which can be addressed in
the future.Signed-off-by: Badari Pulavarty
Cc: Hugh Dickins
Cc: Andrea Arcangeli
Cc: Michael Kerrisk
Cc: Ulrich Drepper
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
