Mel Gorman
04f2cbe356
hugetlb: guarantee that COW faults for a process that called mmap(MAP_PRIVATE) on hugetlbfs will succeed ...
After patch 2 in this series, a process that successfully calls mmap() for
a MAP_PRIVATE mapping will be guaranteed to successfully fault until a
process calls fork(). At that point, the next write fault from the parent
could fail due to COW if the child still has a reference.
We only reserve pages for the parent but a copy must be made to avoid
leaking data from the parent to the child after fork(). Reserves could be
taken for both parent and child at fork time to guarantee faults but if
the mapping is large it is highly likely we will not have sufficient pages
for the reservation, and it is common to fork only to exec() immediatly
after. A failure here would be very undesirable.
Note that the current behaviour of mainline with MAP_PRIVATE pages is
pretty bad. The following situation is allowed to occur today.
1. Process calls mmap(MAP_PRIVATE)
2. Process calls mlock() to fault all pages and makes sure it succeeds
3. Process forks()
4. Process writes to MAP_PRIVATE mapping while child still exists
5. If the COW fails at this point, the process gets SIGKILLed even though it
had taken care to ensure the pages existed
This patch improves the situation by guaranteeing the reliability of the
process that successfully calls mmap(). When the parent performs COW, it
will try to satisfy the allocation without using reserves. If that fails
the parent will steal the page leaving any children without a page.
Faults from the child after that point will result in failure. If the
child COW happens first, an attempt will be made to allocate the page
without reserves and the child will get SIGKILLed on failure.
To summarise the new behaviour:
1. If the original mapper performs COW on a private mapping with multiple
references, it will attempt to allocate a hugepage from the pool or
the buddy allocator without using the existing reserves. On fail, VMAs
mapping the same area are traversed and the page being COW'd is unmapped
where found. It will then steal the original page as the last mapper in
the normal way.
2. The VMAs the pages were unmapped from are flagged to note that pages
with data no longer exist. Future no-page faults on those VMAs will
terminate the process as otherwise it would appear that data was corrupted.
A warning is printed to the console that this situation occured.
2. If the child performs COW first, it will attempt to satisfy the COW
from the pool if there are enough pages or via the buddy allocator if
overcommit is allowed and the buddy allocator can satisfy the request. If
it fails, the child will be killed.
If the pool is large enough, existing applications will not notice that
the reserves were a factor. Existing applications depending on the
no-reserves been set are unlikely to exist as for much of the history of
hugetlbfs, pages were prefaulted at mmap(), allocating the pages at that
point or failing the mmap().
[npiggin@suse.de: fix CONFIG_HUGETLB=n build]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-24 10:47:16 -07:00
lockd: Pass "struct sockaddr *" to new failover-by-IP function
2008-07-15 16:11:29 -04:00
Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm
2008-07-23 18:24:08 -07:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/drzeus/mmc
2008-07-16 15:17:52 -07:00
MTD: handle pci_name() being const
2008-07-21 21:55:03 -07:00
netfilter: nfnetlink_log: send complete hardware header
2008-07-21 10:11:00 -07:00
md: Protect access to mddev->disks list using RCU
2008-07-21 17:05:25 +10:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6
2008-07-22 13:13:47 -07:00
Merge branch 'for-2.6.27' of git://linux-nfs.org/~bfields/linux
2008-07-20 21:21:46 -07:00
usb_serial: API all change
2008-07-22 13:03:22 -07:00
Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6
2008-07-16 17:25:46 -07:00
async_tx: remove depend_tx from async_tx_sync_epilog
2008-07-17 17:59:55 -07:00
execve filename: document and export via auxiliary vector
2008-07-22 09:59:40 -07:00
block: Trivial fix for blk_integrity_rq()
2008-07-16 14:51:41 -07:00
mm: unexport __alloc_bootmem_core()
2008-07-24 10:47:14 -07:00
configfs: Allow ->make_item() and ->make_group() to return detailed errors.
2008-07-17 15:21:29 -07:00
Merge branch 'sched/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
2008-07-23 19:36:53 -07:00
cpu hotplug, sched: Introduce cpu_active_map and redo sched domain managment (take 2)
2008-07-18 13:22:25 +02:00
tty: add more tty_port fields
2008-07-20 17:12:38 -07:00
I/OAT: I/OAT version 3.0 support
2008-07-22 17:30:57 -07:00
debugfs: Implement debugfs_remove_recursive()
2008-07-21 21:54:59 -07:00
dm: introduce merge_bvec_fn
2008-07-21 12:00:37 +01:00
driver core: remove DEVICE_ID_SIZE define
2008-07-21 21:54:53 -07:00
dm: introduce merge_bvec_fn
2008-07-21 12:00:37 +01:00
powerpc/cell: Add DMA_ATTR_WEAK_ORDERING dma attribute and use in Cell IOMMU code
2008-07-22 10:39:36 +10:00
async_tx: make async_tx_test_ack a boolean routine
2008-07-17 17:59:56 -07:00
driver core: remove DEVICE_NAME_SIZE define
2008-07-21 21:54:53 -07:00
Freezer: Introduce PF_FREEZER_NOSIG
2008-07-16 23:27:03 +02:00
fix soft lock up at NFS mount via per-SB LRU-list of unused dentries
2008-07-24 10:47:15 -07:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
2008-07-22 19:09:51 -07:00
gianfar: Add magic packet and suspend/resume support.
2008-07-16 17:57:47 -05:00
gs: use tty_port
2008-07-20 17:12:36 -07:00
page allocator: inline some __alloc_pages() wrappers
2008-07-24 10:47:14 -07:00
esp: use tty_port
2008-07-20 17:12:36 -07:00
HID: add n-trig digitizer usage
2008-07-23 15:25:21 +02:00
hugetlb: guarantee that COW faults for a process that called mmap(MAP_PRIVATE) on hugetlbfs will succeed
2008-07-24 10:47:16 -07:00
V4L/DVB (8246): tvaudio: Stop I2C driver ID abuse
2008-07-20 07:18:38 -03:00
ide: remove unused PC_FLAG_DRQ_INTERRUPT
2008-07-23 19:56:01 +02:00
packet: add PACKET_RESERVE sockopt
2008-07-18 18:05:19 -07:00
ptrace children revamp
2008-07-16 18:02:33 -07:00
Merge master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6 into next
2008-07-21 00:55:14 -04:00
Merge branch 'genirq' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
2008-07-15 10:39:22 -07:00
PNP: support optional IRQ resources
2008-07-16 23:27:07 +02:00
ipv6: __KERNEL__ ifdef struct ipv6_devconf
2008-07-21 13:41:16 -07:00
istallion: use tty_port
2008-07-20 17:12:37 -07:00
remove CONFIG_KMOD from core kernel code
2008-07-22 19:24:31 +10:00
kobject: reorder kobject to save space on 64 bit builds
2008-07-21 21:54:56 -07:00
KVM: Support mixed endian machines
2008-07-20 12:42:32 +03:00
KVM: MMU: nuke shadowed pgtable pages and ptes on memslot destruction
2008-07-20 12:42:40 +03:00
mm: drop unneeded pgdat argument from free_area_init_node()
2008-07-24 10:47:16 -07:00
module: turn longs into ints for module sizes
2008-07-22 19:24:27 +10:00
net: Fix build failure with 'make mandocs'.
2008-07-22 14:09:06 -07:00
of_gpio: Should use new <linux/gpio.h> header
2008-07-22 10:39:30 +10:00
slob: record page flag overlays explicitly
2008-07-24 10:47:15 -07:00
mapping_set_error: add unlikely()
2008-07-24 10:47:15 -07:00
Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6
2008-07-16 17:25:46 -07:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx
2008-07-23 12:03:18 -07:00
net_sched: Add size table for qdiscs
2008-07-20 00:08:47 -07:00
PNP: convert resource options to single linked list
2008-07-16 23:27:07 +02:00
netns: make get_proc_net() static
2008-07-22 14:19:19 -07:00
net_sched: Add size table for qdiscs
2008-07-20 00:08:47 -07:00
sg: reimplement sg mapping iterator
2008-07-23 14:42:09 +02:00
add a helper function to test if an object is on the stack
2008-07-24 10:47:14 -07:00
proc: consolidate per-net single-release callers
2008-07-18 04:07:44 -07:00
serial: use tty_port
2008-07-20 17:12:35 -07:00
net: Use standard structures for generic socket address structures.
2008-07-19 22:35:47 -07:00
stallion: use tty_port
2008-07-20 17:12:37 -07:00
move memory_read_from_buffer() from fs.h to string.h
2008-07-24 10:47:13 -07:00
synclink_gt: add serial bit order control
2008-07-22 13:03:29 -07:00
sysdev: Add utility functions for simple int/ulong variable sysdev attributes
2008-07-21 21:55:02 -07:00
driver core: Suppress sysfs warnings for device_rename().
2008-07-21 21:55:01 -07:00
tcp: Remove redundant checks when setting eff_sacks
2008-07-19 00:07:02 -07:00
tty: Split ldisc code into its own file
2008-07-22 13:03:27 -07:00
tty: rework break handling
2008-07-22 13:03:28 -07:00
tty: Ldisc revamp
2008-07-20 17:12:34 -07:00
UIO: minor style and comment fixes
2008-07-21 21:54:55 -07:00
USB: Force unbinding of drivers lacking reset_resume or other methods
2008-07-21 15:16:40 -07:00
USB: remove CVS keywords
2008-07-21 15:15:55 -07:00
V4L/DVB (8197): gspca: pac207 frames no more decoded in the subdriver.
2008-07-20 07:17:02 -03:00
mm/vmstat.c: proper externs
2008-07-24 10:47:14 -07:00
Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
2008-07-15 08:36:38 -07:00
