Commit Graph

1864 Commits

Author SHA1 Message Date
Paul Mundt f905bc447c nommu: add new vmalloc_user() and remap_vmalloc_range() interfaces.
This builds on top of the earlier vmalloc_32_user() work introduced by
b50731732f, as we now have places in the nommu
allmodconfig that hit up against these missing APIs.

As vmalloc_32_user() is already implemented, this is moved over to
vmalloc_user() and simply made a wrapper.  As all current nommu platforms are
32-bit addressable, there's no special casing we have to do for ZONE_DMA and
things of that nature as per GFP_VMALLOC32.

remap_vmalloc_range() needs to check VM_USERMAP in order to figure out whether
we permit the remap or not, which means that we also have to rework the
vmalloc_user() code to grovel for the VMA and set the flag.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: David McCullough <david_mccullough@securecomputing.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:21 -08:00
Serge E. Hallyn 97829955ad oom_kill: remove uid==0 checks
Root processes are considered more important when out of memory and killing
proceses.  The check for CAP_SYS_ADMIN was augmented with a check for
uid==0 or euid==0.

There are several possible ways to look at this:

	1. uid comparisons are unnecessary, trust CAP_SYS_ADMIN
	   alone.  However CAP_SYS_RESOURCE is the one that really
	   means "give me extra resources" so allow for that as
	   well.
	2. Any privileged code should be protected, but uid is not
	   an indication of privilege.  So we should check whether
	   any capabilities are raised.
	3. uid==0 makes processes on the host as well as in containers
	   more important, so we should keep the existing checks.
	4. uid==0 makes processes only on the host more important,
	   even without any capabilities.  So we should be keeping
	   the (uid==0||euid==0) check but only when
	   userns==&init_user_ns.

I'm following number 1 here.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Cc: Andrew Morgan <morgan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:20 -08:00
Andrew Morgan e338d263a7 Add 64-bit capability support to the kernel
The patch supports legacy (32-bit) capability userspace, and where possible
translates 32-bit capabilities to/from userspace and the VFS to 64-bit
kernel space capabilities.  If a capability set cannot be compressed into
32-bits for consumption by user space, the system call fails, with -ERANGE.

FWIW libcap-2.00 supports this change (and earlier capability formats)

 http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.6/

[akpm@linux-foundation.org: coding-syle fixes]
[akpm@linux-foundation.org: use get_task_comm()]
[ezk@cs.sunysb.edu: build fix]
[akpm@linux-foundation.org: do not initialise statics to 0 or NULL]
[akpm@linux-foundation.org: unused var]
[serue@us.ibm.com: export __cap_ symbols]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: James Morris <jmorris@namei.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:20 -08:00
David P. Quigley 4249259404 VFS/Security: Rework inode_getsecurity and callers to return resulting buffer
This patch modifies the interface to inode_getsecurity to have the function
return a buffer containing the security blob and its length via parameters
instead of relying on the calling function to give it an appropriately sized
buffer.

Security blobs obtained with this function should be freed using the
release_secctx LSM hook.  This alleviates the problem of the caller having to
guess a length and preallocate a buffer for this function allowing it to be
used elsewhere for Labeled NFS.

The patch also removed the unused err parameter.  The conversion is similar to
the one performed by Al Viro for the security_getprocattr hook.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:20 -08:00
Matt Mackall 20cecbae44 slob: reduce external fragmentation by using three free lists
By putting smaller objects on their own list, we greatly reduce overall
external fragmentation and increase repeatability.  This reduces total SLOB
overhead from > 50% to ~6% on a simple boot test.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Matt Mackall 679299b32d slob: fix free block merging at head of subpage
We weren't merging freed blocks at the beginning of the free list.  Fixing
this showed a 2.5% efficiency improvement in a userspace test harness.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Fengguang Wu 8bc3be2751 writeback: speed up writeback of big dirty files
After making dirty a 100M file, the normal behavior is to start the
writeback for all data after 30s delays.  But sometimes the following
happens instead:

	- after 30s:    ~4M
	- after 5s:     ~4M
	- after 5s:     all remaining 92M

Some analyze shows that the internal io dispatch queues goes like this:

		s_io            s_more_io
		-------------------------
	1)	100M,1K         0
	2)	1K              96M
	3)	0               96M
1) initial state with a 100M file and a 1K file

2) 4M written, nr_to_write <= 0, so write more

3) 1K written, nr_to_write > 0, no more writes(BUG)

nr_to_write > 0 in (3) fools the upper layer to think that data have all
been written out.  The big dirty file is actually still sitting in
s_more_io.  We cannot simply splice s_more_io back to s_io as soon as s_io
becomes empty, and let the loop in generic_sync_sb_inodes() continue: this
may starve newly expired inodes in s_dirty.  It is also not an option to
draw inodes from both s_more_io and s_dirty, an let the loop go on: this
might lead to live locks, and might also starve other superblocks in sync
time(well kupdate may still starve some superblocks, that's another bug).

We have to return when a full scan of s_io completes.  So nr_to_write > 0
does not necessarily mean that "all data are written".  This patch
introduces a flag writeback_control.more_io to indicate that more io should
be done.  With it the big dirty file no longer has to wait for the next
kupdate invokation 5s later.

In sync_sb_inodes() we only set more_io on super_blocks we actually
visited.  This avoids the interaction between two pdflush deamons.

Also in __sync_single_inode() we don't blindly keep requeuing the io if the
filesystem cannot progress.  Failing to do so may lead to 100% iowait.

Tested-by: Mike Snitzer <snitzer@gmail.com>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Sam Ravnborg a322f8ab66 mm: fix section mismatch warning in sparse.c
Fix following warning:
WARNING: mm/built-in.o(.text+0x22069): Section mismatch in reference from the function sparse_early_usemap_alloc() to the function .init.text:__alloc_bootmem_node()

static sparse_early_usemap_alloc() were used only by sparse_init()
and with sparse_init() annotated _init it is safe to
annotate sparse_early_usemap_alloc with __init too.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Nick Piggin 0ed361dec3 mm: fix PageUptodate data race
After running SetPageUptodate, preceeding stores to the page contents to
actually bring it uptodate may not be ordered with the store to set the
page uptodate.

Therefore, another CPU which checks PageUptodate is true, then reads the
page contents can get stale data.

Fix this by having an smp_wmb before SetPageUptodate, and smp_rmb after
PageUptodate.

Many places that test PageUptodate, do so with the page locked, and this
would be enough to ensure memory ordering in those places if
SetPageUptodate were only called while the page is locked.  Unfortunately
that is not always the case for some filesystems, but it could be an idea
for the future.

Also bring the handling of anonymous page uptodateness in line with that of
file backed page management, by marking anon pages as uptodate when they
_are_ uptodate, rather than when our implementation requires that they be
marked as such.  Doing allows us to get rid of the smp_wmb's in the page
copying functions, which were especially added for anonymous pages for an
analogous memory ordering problem.  Both file and anonymous pages are
handled with the same barriers.

FAQ:
Q. Why not do this in flush_dcache_page?
A. Firstly, flush_dcache_page handles only one side (the smb side) of the
ordering protocol; we'd still need smp_rmb somewhere. Secondly, hiding away
memory barriers in a completely unrelated function is nasty; at least in the
PageUptodate macros, they are located together with (half) the operations
involved in the ordering. Thirdly, the smp_wmb is only required when first
bringing the page uptodate, wheras flush_dcache_page should be called each time
it is written to through the kernel mapping. It is logically the wrong place to
put it.

Q. Why does this increase my text size / reduce my performance / etc.
A. Because it is adding the necessary instructions to eliminate the data-race.

Q. Can it be improved?
A. Yes, eg. if you were to create a rule that all SetPageUptodate operations
run under the page lock, we could avoid the smp_rmb places where PageUptodate
is queried under the page lock. Requires audit of all filesystems and at least
some would need reworking. That's great you're interested, I'm eagerly awaiting
your patches.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Shaohua Li 62e1c55300 page migraton: handle orphaned pages
Orphaned page might have fs-private metadata, the page is truncated.  As
the page hasn't mapping, page migration refuse to migrate the page.  It
appears the page is only freed in page reclaim and if zone watermark is
low, the page is never freed, as a result migration always fail.  I thought
we could free the metadata so such page can be freed in migration and make
migration more reliable.

[akpm@linux-foundation.org: go direct to try_to_free_buffers()]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Masatake YAMATO b5beb1caff check ADVICE of fadvise64_64 even if get_xip_page is given
I've written some test programs in ltp project.  During writing I met an
problem which I cannot solve in user land.  So I wrote a patch for linux
kernel.  Please, include this patch if acceptable.

The test program tests the 4th parameter of fadvise64_64:

    long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice);

My test case calls fadvise64_64 with invalid advice value and checks errno is
set to EINVAL.  About the advice parameter man page says:

    ...
    Permissible values for advice include:

	   POSIX_FADV_NORMAL
                  ...
	   POSIX_FADV_SEQUENTIAL
                  ...
	   POSIX_FADV_RANDOM
		  ...
	   POSIX_FADV_NOREUSE
                  ...
	   POSIX_FADV_WILLNEED
                  ...
	   POSIX_FADV_DONTNEED
		  ...
    ERRORS
           ...
	   EINVAL An invalid value was specified for advice.

However, I got a bug report that the system call invocations
in my test case returned 0 unexpectedly.

I've inspected the kernel code:

    asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
    {
	    struct file *file = fget(fd);
	    struct address_space *mapping;
	    struct backing_dev_info *bdi;
	    loff_t endbyte;			/* inclusive */
	    pgoff_t start_index;
	    pgoff_t end_index;
	    unsigned long nrpages;
	    int ret = 0;

	    if (!file)
		    return -EBADF;

	    if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) {
		    ret = -ESPIPE;
		    goto out;
	    }

	    mapping = file->f_mapping;
	    if (!mapping || len < 0) {
		    ret = -EINVAL;
		    goto out;
	    }

	    if (mapping->a_ops->get_xip_page)
		    /* no bad return value, but ignore advice */
		    goto out;
    ...
    out:
	    fput(file);
	    return ret;
    }

I found the advice parameter is just ignored in the case
mapping->a_ops->get_xip_page is given. This behavior is different from
what is written on the man page. Is this o.k.?

get_xip_page is given if CONFIG_EXT2_FS_XIP is true.
Anyway I cannot find the easy way to detect get_xip_page
field is given or CONFIG_EXT2_FS_XIP is true from the
user space.

I propose the following patch which checks the advice parameter
even if get_xip_page is given.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Larry Woodman e6f3602d2c Include count of pagecache pages in show_mem() output
The show_mem() output does not include the total number of pagecache
pages.  This would be helpful when analyzing the debug information in
the /var/log/messages file after OOM kills occur.

This patch includes the total pagecache pages in that output.

Signed-off-by: Larry Woodman <lwoodman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Bjorn Steinbrink a2b345642f Fix dirty page accounting leak with ext3 data=journal
In 46d2277c79 ("Clean up and make
try_to_free_buffers() not race with dirty pages"), try_to_free_buffers
was changed to bail out if the page was dirty.

That in turn caused truncate_complete_page to leak massive amounts of
memory, because the dirty bit was only cleared after the call to
try_to_free_buffers.

So the call to cancel_dirty_page was moved up to have the dirty bit
cleared early in 3e67c0987d ("truncate:
clear page dirtiness before running try_to_free_buffers()").

The problem with that fix is, that the page can be redirtied after
cancel_dirty_page was called, eg. like this:

truncate_complete_page()
  cancel_dirty_page() // PG_dirty cleared, decr. dirty pages
  do_invalidatepage()
    ext3_invalidatepage()
      journal_invalidatepage()
        journal_unmap_buffer()
          __dispose_buffer()
            __journal_unfile_buffer()
              __journal_temp_unlink_buffer()
                mark_buffer_dirty(); // PG_dirty set, incr. dirty pages

And then we end up with dirty pages being wrongly accounted.

As a result, in ecdfc9787f ("Resurrect
'try_to_free_buffers()' VM hackery") the changes to try_to_free_buffers
were reverted, so the original reason for the massive memory leak is
gone, and we can also revert the move of the call to cancel_dirty_page
from truncate_complete_page and get the accounting right again.

I'm not sure if it matters, but opposed to the final check in
__remove_from_page_cache, this one also cares about the task io
accounting, so maybe we want to use this instead, although it's not
quite the clean fix either.

Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Cc: Jan Kara <jack@ucw.cz>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Osterried <osterried@jesse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Qi Yong ae1276b934 set_page_refcounted() VM_BUG_ON fix
The current PageTail semantic is that a PageTail page is first a
PageCompound page.  So remove the redundant PageCompound test in
set_page_refcounted().

Signed-off-by: Qi Yong <qiyong@fc-cn.com>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00
Harvey Harrison 920c7a5d0c mm: remove fastcall from mm/
fastcall is always defined to be empty, remove it

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Andi Kleen 1e548deb5d page allocator: remove unused arguments in zone_init_free_lists()
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Hugh Dickins 5a9bbdcd29 mm: don't waste swap on locked pages
try_to_unmap always fails on a page found in a VM_LOCKED vma (unless
migrating), and recycles it back to the active list.  But if it's an
anonymous page, we've already allocated swap to it: just wasting swap.
Spot locked pages in page_referenced_one and treat them as referenced.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ethan Solomita <solo@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Christoph Lameter 9eccf2a816 vmstat: remove prefetch
Remove the prefetch logic in order to avoid touching impossible per cpu
areas.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Bron Gondwana 195cf453d2 mm/page-writeback: highmem_is_dirtyable option
Add vm.highmem_is_dirtyable toggle

A 32 bit machine with HIGHMEM64 enabled running DCC has an MMAPed file of
approximately 2Gb size which contains a hash format that is written
randomly by the dbclean process.  On 2.6.16 this process took a few
minutes.  With lowmem only accounting of dirty ratios, this takes about 12
hours of 100% disk IO, all random writes.

Include a toggle in /proc/sys/vm/highmem_is_dirtyable which can be set to 1 to
add the highmem back to the total available memory count.

[akpm@linux-foundation.org: Fix the CONFIG_DETECT_SOFTLOCKUP=y build]
Signed-off-by: Bron Gondwana <brong@fastmail.fm>
Cc: Ethan Solomita <solo@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: WU Fengguang <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Christoph Lameter 3dfa5721f1 Page allocator: get rid of the list of cold pages
We have repeatedly discussed if the cold pages still have a point. There is
one way to join the two lists: Use a single list and put the cold pages at the
end and the hot pages at the beginning. That way a single list can serve for
both types of allocations.

The discussion of the RFC for this and Mel's measurements indicate that
there may not be too much of a point left to having separate lists for
hot and cold pages (see http://marc.info/?t=119492914200001&r=1&w=2).

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Martin Bligh <mbligh@mbligh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Robert Bragg 5dc3318528 mm: don't allow ioremapping of ranges larger than vmalloc space
When running with a 16M IOREMAP_MAX_ORDER (on armv7) we found that the
vmlist search routine in __get_vm_area_node can mistakenly allow a driver
to ioremap a range larger than vmalloc space.

If at the time of the ioremap all existing vmlist areas sit below the
determined alignment then the search routine continues past all entries and
exits the for loop - straight into the found: label - without ever testing
for integer wrapping or that the requested size fits.

We were seeing a driver successfully ioremap 128M of flash even though
there was only 120M of vmalloc space.  From that point the system was left
with the remainder of the first 16M of space to vmalloc/ioremap within.

Signed-off-by: Robert Bragg <robert@sixbynine.org>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Christoph Lameter a7f75e2586 vmstat: small revisions to refresh_cpu_vm_stats()
1. Add comments explaining how the function can be called.

2. Collect global diffs in a local array and only spill
   them once into the global counters when the zone scan
   is finished. This means that we only touch each global
   counter once instead of each time we fold cpu counters
   into zone counters.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Martin Schwidefsky 08e7d9b557 arch_rebalance_pgtables call
In order to change the layout of the page tables after an mmap has crossed the
adress space limit of the current page table layout a architecture hook in
get_unmapped_area is needed.  The arguments are the address of the new mapping
and the length of it.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Benjamin Herrenschmidt 5e5419734c add mm argument to pte/pmd/pud/pgd_free
(with Martin Schwidefsky <schwidefsky@de.ibm.com>)

The pgd/pud/pmd/pte page table allocation functions get a mm_struct pointer as
first argument.  The free functions do not get the mm_struct argument.  This
is 1) asymmetrical and 2) to do mm related page table allocations the mm
argument is needed on the free function as well.

[kamalesh@linux.vnet.ibm.com: i386 fix]
[akpm@linux-foundation.org: coding-syle fixes]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:18 -08:00
Christoph Lameter 9f8f217253 Page allocator: clean up pcp draining functions
- Add comments explaing how drain_pages() works.

- Eliminate useless functions

- Rename drain_all_local_pages to drain_all_pages(). It does drain
  all pages not only those of the local processor.

- Eliminate useless interrupt off / on sequences. drain_pages()
  disables interrupts on its own. The execution thread is
  pinned to processor by the caller. So there is no need to
  disable interrupts.

- Put drain_all_pages() declaration in gfp.h and remove the
  declarations from suspend.h and from mm/memory_hotplug.c

- Make software suspend call drain_all_pages(). The draining
  of processor local pages is may not the right approach if
  software suspend wants to support SMP. If they call drain_all_pages
  then we can make drain_pages() static.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Daniel Walker <dwalker@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Nick Piggin e2848a0efe radix-tree: avoid atomic allocations for preloaded insertions
Most pagecache (and some other) radix tree insertions have the great
opportunity to preallocate a few nodes with relaxed gfp flags.  But the
preallocation is squandered when it comes time to allocate a node, we
default to first attempting a GFP_ATOMIC allocation -- that doesn't
normally fail, but it can eat into atomic memory reserves that we don't
need to be using.

Another upshot of this is that it removes the sometimes highly contended
zone->lock from underneath tree_lock.  Pagecache insertions are always
performed with a radix tree preload, and after this change, such a
situation will never fall back to kmem_cache_alloc within
radix_tree_node_alloc.

David Miller reports seeing this allocation fail on a highly threaded
sparc64 system:

[527319.459981] dd: page allocation failure. order:0, mode:0x20
[527319.460403] Call Trace:
[527319.460568]  [00000000004b71e0] __slab_alloc+0x1b0/0x6a8
[527319.460636]  [00000000004b7bbc] kmem_cache_alloc+0x4c/0xa8
[527319.460698]  [000000000055309c] radix_tree_node_alloc+0x20/0x90
[527319.460763]  [0000000000553238] radix_tree_insert+0x12c/0x260
[527319.460830]  [0000000000495cd0] add_to_page_cache+0x38/0xb0
[527319.460893]  [00000000004e4794] mpage_readpages+0x6c/0x134
[527319.460955]  [000000000049c7fc] __do_page_cache_readahead+0x170/0x280
[527319.461028]  [000000000049cc88] ondemand_readahead+0x208/0x214
[527319.461094]  [0000000000496018] do_generic_mapping_read+0xe8/0x428
[527319.461152]  [0000000000497948] generic_file_aio_read+0x108/0x170
[527319.461217]  [00000000004badac] do_sync_read+0x88/0xd0
[527319.461292]  [00000000004bb5cc] vfs_read+0x78/0x10c
[527319.461361]  [00000000004bb920] sys_read+0x34/0x60
[527319.461424]  [0000000000406294] linux_sparc_syscall32+0x3c/0x40

The calltrace is significant: __do_page_cache_readahead allocates a number
of pages with GFP_KERNEL, and hence it should have reclaimed sufficient
memory to satisfy GFP_ATOMIC allocations.  However after the list of pages
goes to mpage_readpages, there can be significant intervals (including disk
IO) before all the pages are inserted into the radix-tree.  So the reserves
can easily be depleted at that point.  The patch is confirmed to fix the
problem.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Adrian Bunk e31d9eb5c1 make __vmalloc_area_node() static
__vmalloc_area_node() can become static.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Balbir Singh 625d9573d0 Remove unused code from mm/tiny-shmem.c
This code in mm/tiny-shmem.c is under #if 0 - remove it.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Adrian Bunk f61eaf9fc5 mm/page-writeback.c: make a function static
task_dirty_limit() can become static.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Matt Mackall 1e88328111 maps4: make page monitoring /proc file optional
Make /proc/ page monitoring configurable

This puts the following files under an embedded config option:

/proc/pid/clear_refs
/proc/pid/smaps
/proc/pid/pagemap
/proc/kpagecount
/proc/kpageflags

[akpm@linux-foundation.org: Kconfig fix]
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:17 -08:00
Matt Mackall e6473092bd maps4: introduce a generic page walker
Introduce a general page table walker

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:16 -08:00
Matt Mackall 698dd4ba6b maps4: move is_swap_pte
Move is_swap_pte helper function to swapops.h for use by pagemap code

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:16 -08:00
Christoph Hellwig 61d5048f14 clean up vmtruncate
vmtruncate is a twisted maze of gotos, this patch cleans it up to have a
proper if else for the two major cases of extending and truncating truncate
and thus makes it a lot more readable while keeping exactly the same
functinality.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:16 -08:00
Hugh Dickins 1b1b32f2c6 tmpfs: fix shmem_swaplist races
Intensive swapoff testing shows shmem_unuse spinning on an entry in
shmem_swaplist pointing to itself: how does that come about?  Days pass...

First guess is this: shmem_delete_inode tests list_empty without taking the
global mutex (so the swapping case doesn't slow down the common case); but
there's an instant in shmem_unuse_inode's list_move_tail when the list entry
may appear empty (a rare case, because it's actually moving the head not the
the list member).  So there's a danger of leaving the inode on the swaplist
when it's freed, then reinitialized to point to itself when reused.  Fix that
by skipping the list_move_tail when it's a no-op, which happens to plug this.

But this same spinning then surfaces on another machine.  Ah, I'd never
suspected it, but shmem_writepage's swaplist manipulation is unsafe: though we
still hold page lock, which would hold off inode deletion if the page were in
pagecache, it doesn't hold off once it's in swapcache (free_swap_and_cache
doesn't wait on locked pages).  Hmm: we could put the the inode on swaplist
earlier, but then shmem_unuse_inode could never prune unswapped inodes.

Fix this with an igrab before dropping info->lock, as in shmem_unuse_inode;
though I am a little uneasy about the iput which has to follow - it works, and
I see nothing wrong with it, but it is surprising that shmem inode deletion
may now occur below shmem_writepage.  Revisit this fix later?

And while we're looking at these races: the way shmem_unuse tests swapped
without holding info->lock looks unsafe, if we've more than one swap area: a
racing shmem_writepage on another page of the same inode could be putting it
in swapcache, just as we're deciding to remove the inode from swaplist -
there's a danger of going on swap without being listed, so a later swapoff
would hang, being unable to locate the entry.  Move that test and removal down
into shmem_unuse_inode, once info->lock is held.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:16 -08:00
Hugh Dickins b409f9fcf0 tmpfs: radix_tree_preloading
Nick has observed that shmem.c still uses GFP_ATOMIC when adding to page cache
or swap cache, without any radix tree preload: so tending to deplete emergency
reserves of memory.

GFP_ATOMIC remains appropriate in shmem_writepage's add_to_swap_cache: it's
being called under memory pressure, so must not wait for more memory to become
available.  But shmem_unuse_inode now has a window in which it can and should
preload with GFP_KERNEL, and say GFP_NOWAIT instead of GFP_ATOMIC in its
add_to_page_cache.

shmem_getpage is not so straightforward: its filepage/swappage integrity
relies upon exchanging between caches under spinlock, and it would need a lot
of restructuring to place the preloads correctly.  Instead, follow its pattern
of retrying on races: use GFP_NOWAIT instead of GFP_ATOMIC in
add_to_page_cache, and begin each circuit of the repeat loop with a sleeping
radix_tree_preload, followed immediately by radix_tree_preload_end - that
won't guarantee success in the next add_to_page_cache, but doesn't need to.

And we can then remove that bothersome congestion_wait: when needed, it'll
automatically get done in the course of the radix_tree_preload.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Looks-good-to: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 2e0e26c76a tmpfs: open a window in shmem_unuse_inode
There are a couple of reasons (patches follow) why it would be good to open a
window for sleep in shmem_unuse_inode, between its search for a matching swap
entry, and its handling of the entry found.

shmem_unuse_inode must then use igrab to hold the inode against deletion in
that window, and its corresponding iput might result in deletion: so it had
better unlock_page before the iput, and might as well release the page too.

Nor is there any need to hold on to shmem_swaplist_mutex once we know we'll
leave the loop.  So this unwinding moves from try_to_unuse and shmem_unuse
into shmem_unuse_inode, in the case when it finds a match.

Let try_to_unuse break on error in the shmem_unuse case, as it does in the
unuse_mm case: though at this point in the series, no error to break on.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins cb5f7b9a47 tmpfs: make shmem_unuse more preemptible
shmem_unuse is at present an unbroken search through every swap vector page of
every tmpfs file which might be swapped, all under shmem_swaplist_lock.  This
dates from long ago, when the caller held mmlist_lock over it all too: long
gone, but there's never been much pressure for preemptible swapoff.

Make it a little more preemptible, replacing shmem_swaplist_lock by
shmem_swaplist_mutex, inserting a cond_resched in the main loop, and a
cond_resched_lock (on info->lock) at one convenient point in the
shmem_unuse_inode loop, where it has no outstanding kmap_atomic.

If we're serious about preemptible swapoff, there's much further to go e.g.
I'm stupid to let the kmap_atomics of the decreasingly significant HIGHMEM
case dictate preemptiblility for other configs.  But as in the earlier patch
to make swapoff scan ptes preemptibly, my hidden agenda is really towards
making memcgroups work, hardly about preemptibility at all.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins a0ee5ec520 tmpfs: allocate on read when stacked
tmpfs is expected to limit the memory used (unless mounted with nr_blocks=0 or
size=0).  But if a stacked filesystem such as unionfs gets pages from a sparse
tmpfs file by reading holes, and then writes to them, it can easily exceed any
such limit at present.

So suppress the SGP_READ "don't allocate page" ZERO_PAGE optimization when
reading for the kernel (a KERNEL_DS check, ugh, sorry about that).  Indeed,
pessimistically mark such pages as dirty, so they cannot get reclaimed and
unaccounted by mistake.  The venerable shmem_recalc_inode code (originally to
account for the reclaim of clean pages) suffices to get the accounting right
when swappages are dropped in favour of more uptodate filepages.

This also fixes the NULL shmem_swp_entry BUG or oops in shmem_writepage,
caused by unionfs writing to a very sparse tmpfs file: to minimize memory
allocation in swapout, tmpfs requires the swap vector be allocated upfront,
which wasn't always happening in this stacked case.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins d9fe526a83 tmpfs: allow filepage alongside swappage
tmpfs has long allowed for a fresh filepage to be created in pagecache, just
before shmem_getpage gets the chance to match it up with the swappage which
already belongs to that offset.  But unionfs_writepage now does a
find_or_create_page, divorced from shmem_getpage, which leaves conflicting
filepage and swappage outstanding indefinitely, when unionfs is over tmpfs.

Therefore shmem_writepage (where a page is swizzled from file to swap) must
now be on the lookout for existing swap, ready to free it in favour of the
more uptodate filepage, instead of BUGging on that clash.  And when the
add_to_page_cache fails in shmem_unuse_inode, it must defer to an uptodate
filepage, otherwise swapoff would hang.  Whereas when add_to_page_cache fails
in shmem_getpage, it should retry in the same way it already does.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 73b1262fa4 tmpfs: move swap swizzling into shmem
move_to_swap_cache and move_from_swap_cache functions (which swizzle a page
between tmpfs page cache and swap cache, to avoid page copying) are only used
by shmem.c; and our subsequent fix for unionfs needs different treatments in
the two instances of move_from_swap_cache.  Move them from swap_state.c into
their callsites shmem_writepage, shmem_unuse_inode and shmem_getpage, making
add_to_swap_cache externally visible.

shmem.c likes to say set_page_dirty where swap_state.c liked to say
SetPageDirty: respect that diversity, which __set_page_dirty_no_writeback
makes moot (and implies we should lose that "shift page from clean_pages to
dirty_pages list" comment: it's on neither).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins f000944d03 tmpfs: shuffle add_to_swap_caches
add_to_swap_cache doesn't amount to much: merge it into its sole caller
read_swap_cache_async.  But we'll be needing to call __add_to_swap_cache from
shmem.c, so promote it to the new add_to_swap_cache.  Both were static, so
there's no interface confusion to worry about.

And lose that inappropriate "Anon pages are already on the LRU" comment in the
merging: they're not already on the LRU, as Nick Piggin noticed.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
No-problems-with: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins bb63be0a09 tmpfs: move swap_state stats update
Both unionfs and memcgroups pose challenges to tmpfs and shmem.  To help fix,
it's best to move the swap swizzling functions from swap_state.c to shmem.c.
As a preliminary to that, move swap stats updating down into
__add_to_swap_cache, which will remain internal to swap_state.c.

Well, actually, just move down the incrementation of add_total: remove
noent_race and exist_race completely, they are relics of my 2.4.11 testing.
Alt-SysRq-m users will be thrilled if 2.6.25 is at last free of "race M+N"s.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Michael Marineau 818db35992 tmpfs: fix mounts when size is less than the page size
When tmpfs is mounted with a size less than one page, the number of blocks
is set to 0 which makes the tmpfs mount unlimited.  This can lead to a
quick and surprising death if someone typos a tmpfs mount command and
writes too much.

tmpfs can still be mounted as unlimited if size or nr_blocks is exactly 0,
as Documentation/filesystems/tmpfs.txt says.

Hugh: do this by rounding size up instead of down in all cases: which
slightly expands other odd-sized tmpfs mounts, but in a consistent way.

Signed-off-by: Michael Marineau <mike@marineau.org>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Pavel Emelyanov 5b04c6890f shmem: factor out sbi->free_inodes manipulations
The shmem_sb_info structure has a number of free_inodes. This
value is altered in appropriate places under spinlock and with
the sbi->max_inodes != 0 check.

Consolidate these manipulations into two helpers.

This is minus 42 bytes of shmem.o and minus 4 :) lines of code.

[akpm@linux-foundation.org: fix error return values]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 2e441889c3 swapoff: scan ptes preemptibly
Provided that CONFIG_HIGHPTE is not set, unuse_pte_range can reduce latency
in swapoff by scanning the page table preemptibly: so long as unuse_pte is
careful to recheck that entry under pte lock.

(To tell the truth, this patch was not inspired by any cries for lower
latency here: rather, this restructuring permits a future memory controller
patch to allocate with GFP_KERNEL in unuse_pte, where before it could not.
But it would be wrong to tuck this change away inside a memcgroup patch.)

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Tested-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 8952898b0d swapin: fix valid_swaphandles defect
valid_swaphandles is supposed to do a quick pass over the swap map entries
neigbouring the entry which swapin_readahead is targetting, to determine for
it a range worth reading all together.  But since it always starts its search
from the beginning of the swap "cluster", a reject (free entry) there
immediately curtails the readaround, and every swapin_readahead from that
cluster is for just a single page.  Instead scan forwards and backwards around
the target entry.

Use better names for some variables: a swap_info pointer is usually called
"si" not "swapdev".  And at the end, if only the target page should be read,
return count of 0 to disable readaround, to avoid the unnecessarily repeated
call to read_swap_cache_async.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 5402b976ae shmem_file_write is redundant
With the old aops, writing to a tmpfs file had to use its own special method:
the generic method would pass in a fresh page to prepare_write when the right
page was there in swapcache - which was inefficient to handle, even once we'd
concocted the code to handle it.

With the new aops, the generic method uses shmem_write_end, which lets
shmem_getpage find the right page: so now abandon shmem_file_write in favour
of the generic method.  Yes, that does do several things that tmpfs hasn't
really needed (notably balance_dirty_pages_ratelimited, which ramfs also
calls); but more use of common code is preferable.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins d3602444e1 shmem_getpage return page locked
In the new aops, write_begin is supposed to return the page locked: though
I've seen no ill effects, that's been overlooked in the case of
shmem_write_begin, and should be fixed.  Then shmem_write_end must unlock the
page: do so _after_ updating i_size, as we found to be important in other
filesystems (though since shmem pages don't go the usual writeback route, they
never suffered from that corruption).

For shmem_write_begin to return the page locked, we need shmem_getpage to
return the page locked in SGP_WRITE case as well as SGP_CACHE case: let's
simplify the interface and return it locked even when SGP_READ.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:15 -08:00
Hugh Dickins 27d54b398e shmem: SGP_QUICK and SGP_FAULT redundant
Remove SGP_QUICK from the sgp_type enum: it was for shmem_populate and has no
users now.  Remove SGP_FAULT from the enum: SGP_CACHE does just as well (and
shmem_getpage is about to return with page always locked).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:14 -08:00
Hugh Dickins 02098feaa4 swapin needs gfp_mask for loop on tmpfs
Building in a filesystem on a loop device on a tmpfs file can hang when
swapping, the loop thread caught in that infamous throttle_vm_writeout.

In theory this is a long standing problem, which I've either never seen in
practice, or long ago suppressed the recollection, after discounting my load
and my tmpfs size as unrealistically high.  But now, with the new aops, it has
become easy to hang on one machine.

Loop used to grab_cache_page before the old prepare_write to tmpfs, which
seems to have been enough to free up some memory for any swapin needed; but
the new write_begin lets tmpfs find or allocate the page (much nicer, since
grab_cache_page missed tmpfs pages in swapcache).

When allocating a fresh page, tmpfs respects loop's mapping_gfp_mask, which
has __GFP_IO|__GFP_FS stripped off, and throttle_vm_writeout is designed to
break out when __GFP_IO or GFP_FS is unset; but when tmfps swaps in,
read_swap_cache_async allocates with GFP_HIGHUSER_MOVABLE regardless of the
mapping_gfp_mask - hence the hang.

So, pass gfp_mask down the line from shmem_getpage to shmem_swapin to
swapin_readahead to read_swap_cache_async to add_to_swap_cache.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:14 -08:00