Commit Graph

95 Commits

Author SHA1 Message Date
David Rientjes
2da02997e0 mm: add dirty_background_bytes and dirty_bytes sysctls
This change introduces two new sysctls to /proc/sys/vm:
dirty_background_bytes and dirty_bytes.

dirty_background_bytes is the counterpart to dirty_background_ratio and
dirty_bytes is the counterpart to dirty_ratio.

With growing memory capacities of individual machines, it's no longer
sufficient to specify dirty thresholds as a percentage of the amount of
dirtyable memory over the entire system.

dirty_background_bytes and dirty_bytes specify quantities of memory, in
bytes, that represent the dirty limits for the entire system.  If either
of these values is set, its value represents the amount of dirty memory
that is needed to commence either background or direct writeback.

When a `bytes' or `ratio' file is written, its counterpart becomes a
function of the written value.  For example, if dirty_bytes is written to
be 8096, 8K of memory is required to commence direct writeback.
dirty_ratio is then functionally equivalent to 8K / the amount of
dirtyable memory:

	dirtyable_memory = free pages + mapped pages + file cache

	dirty_background_bytes = dirty_background_ratio * dirtyable_memory
		-or-
	dirty_background_ratio = dirty_background_bytes / dirtyable_memory

		AND

	dirty_bytes = dirty_ratio * dirtyable_memory
		-or-
	dirty_ratio = dirty_bytes / dirtyable_memory

Only one of dirty_background_bytes and dirty_background_ratio may be
specified at a time, and only one of dirty_bytes and dirty_ratio may be
specified.  When one sysctl is written, the other appears as 0 when read.

The `bytes' files operate on a page size granularity since dirty limits
are compared with ZVC values, which are in page units.

Prior to this change, the minimum dirty_ratio was 5 as implemented by
get_dirty_limits() although /proc/sys/vm/dirty_ratio would show any user
written value between 0 and 100.  This restriction is maintained, but
dirty_bytes has a lower limit of only one page.

Also prior to this change, the dirty_background_ratio could not equal or
exceed dirty_ratio.  This restriction is maintained in addition to
restricting dirty_background_bytes.  If either background threshold equals
or exceeds that of the dirty threshold, it is implicitly set to half the
dirty threshold.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:03 -08:00
David Rientjes
364aeb2849 mm: change dirty limit type specifiers to unsigned long
The background dirty and dirty limits are better defined with type
specifiers of unsigned long since negative writeback thresholds are not
possible.

These values, as returned by get_dirty_limits(), are normally compared
with ZVC values to determine whether writeback shall commence or be
throttled.  Such page counts cannot be negative, so declaring the page
limits as signed is unnecessary.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:02 -08:00
Andrew Morton
82fd1a9a8c mm: write_cache_pages more terminate quickly
Now that we have the early-termination logic in place, it makes sense to
bail out early in all other cases where done is set to 1.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:00 -08:00
Nick Piggin
d5482cdf8a mm: write_cache_pages terminate quickly
Terminate the write_cache_pages loop upon encountering the first page past
end, without locking the page.  Pages cannot have their index change when
we have a reference on them (truncate, eg truncate_inode_pages_range
performs the same check without the page lock).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:00 -08:00
Nick Piggin
515f4a037f mm: write_cache_pages optimise page cleaning
In write_cache_pages, if we get stuck behind another process that is
cleaning pages, we will be forced to wait for them to finish, then perform
our own writeout (if it was redirtied during the long wait), then wait for
that.

If a page under writeout is still clean, we can skip waiting for it (if
we're part of a data integrity sync, we'll be waiting for all writeout
pages afterwards, so we'll still be waiting for the other guy's write
that's cleaned the page).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Nick Piggin
5a3d5c9813 mm: write_cache_pages cleanups
Get rid of some complex expressions from flow control statements, add a
comment, remove some duplicate code.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Nick Piggin
05fe478dd0 mm: write_cache_pages integrity fix
In write_cache_pages, nr_to_write is heeded even for data-integrity syncs,
so the function will return success after writing out nr_to_write pages,
even if that was not sufficient to guarantee data integrity.

The callers tend to set it to values that could break data interity
semantics easily in practice.  For example, nr_to_write can be set to
mapping->nr_pages * 2, however if a file has a single, dirty page, then
fsync is called, subsequent pages might be concurrently added and dirtied,
then write_cache_pages might writeout two of these newly dirty pages,
while not writing out the old page that should have been written out.

Fix this by ignoring nr_to_write if it is a data integrity sync.

This is a data integrity bug.

The reason this has been done in the past is to avoid stalling sync
operations behind page dirtiers.

 "If a file has one dirty page at offset 1000000000000000 then someone
  does an fsync() and someone else gets in first and starts madly writing
  pages at offset 0, we want to write that page at 1000000000000000.
  Somehow."

What we do today is return success after an arbitrary amount of pages are
written, whether or not we have provided the data-integrity semantics that
the caller has asked for.  Even this doesn't actually fix all stall cases
completely: in the above situation, if the file has a huge number of pages
in pagecache (but not dirty), then mapping->nrpages is going to be huge,
even if pages are being dirtied.

This change does indeed make the possibility of long stalls lager, and
that's not a good thing, but lying about data integrity is even worse.  We
have to either perform the sync, or return -ELINUXISLAME so at least the
caller knows what has happened.

There are subsequent competing approaches in the works to solve the stall
problems properly, without compromising data integrity.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Nick Piggin
00266770b8 mm: write_cache_pages writepage error fix
In write_cache_pages, if ret signals a real error, but we still have some
pages left in the pagevec, done would be set to 1, but the remaining pages
would continue to be processed and ret will be overwritten in the process.

It could easily be overwritten with success, and thus success will be
returned even if there is an error.  Thus the caller is told all writes
succeeded, wheras in reality some did not.

Fix this by bailing immediately if there is an error, and retaining the
first error code.

This is a data integrity bug.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Nick Piggin
bd19e012f6 mm: write_cache_pages early loop termination
We'd like to break out of the loop early in many situations, however the
existing code has been setting mapping->writeback_index past the final
page in the pagevec lookup for cyclic writeback.  This is a problem if we
don't process all pages up to the final page.

Currently the code mostly keeps writeback_index reasonable and hacked
around this by not breaking out of the loop or writing pages outside the
range in these cases.  Keep track of a real "done index" that enables us
to terminate the loop in a much more flexible manner.

Needed by the subsequent patch to preserve writepage errors, and then
further patches to break out of the loop early for other reasons.  However
there are no functional changes with this patch alone.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Nick Piggin
31a12666d8 mm: write_cache_pages cyclic fix
In write_cache_pages, scanned == 1 is supposed to mean that cyclic
writeback has circled through zero, thus we should not circle again.
However it gets set to 1 after the first successful pagevec lookup.  This
leads to cases where not enough data gets written.

Counterexample: file with first 10 pages dirty, writeback_index == 5,
nr_to_write == 10.  Then the 5 last pages will be found, and scanned will
be set to 1, after writing those out, we will not cycle back to get the
first 5.

Rework this logic, now we'll always cycle unless we started off from index
0.  When cycling, only write out as far as 1 page before the start page
from the first cycle (so we don't write parts of the file twice).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:58:59 -08:00
Rik van Riel
4f98a2fee8 vmscan: split LRU lists into anon & file sets
Split the LRU lists in two, one set for pages that are backed by real file
systems ("file") and one for pages that are backed by memory and swap
("anon").  The latter includes tmpfs.

The advantage of doing this is that the VM will not have to scan over lots
of anonymous pages (which we generally do not want to swap out), just to
find the page cache pages that it should evict.

This patch has the infrastructure and a basic policy to balance how much
we scan the anon lists and how much we scan the file lists.  The big
policy changes are in separate patches.

[lee.schermerhorn@hp.com: collect lru meminfo statistics from correct offset]
[kosaki.motohiro@jp.fujitsu.com: prevent incorrect oom under split_lru]
[kosaki.motohiro@jp.fujitsu.com: fix pagevec_move_tail() doesn't treat unevictable page]
[hugh@veritas.com: memcg swapbacked pages active]
[hugh@veritas.com: splitlru: BDI_CAP_SWAP_BACKED]
[akpm@linux-foundation.org: fix /proc/vmstat units]
[nishimura@mxp.nes.nec.co.jp: memcg: fix handling of shmem migration]
[kosaki.motohiro@jp.fujitsu.com: adjust Quicklists field of /proc/meminfo]
[kosaki.motohiro@jp.fujitsu.com: fix style issue of get_scan_ratio()]
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-10-20 08:50:25 -07:00
Aneesh Kumar K.V
17bc6c30cf vfs: Add no_nrwrite_index_update writeback control flag
If no_nrwrite_index_update is set we don't update nr_to_write and
address space writeback_index in write_cache_pages.  This change
enables a file system to skip these updates in write_cache_pages and do
them in the writepages() callback.  This patch will be followed by an
ext4 patch that make use of these new flags.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
CC: linux-fsdevel@vger.kernel.org
2008-10-16 10:09:17 -04:00
Aneesh Kumar K.V
74baaaaec8 vfs: Remove the range_cont writeback mode.
Ext4 was the only user of range_cont writeback mode and ext4 switched
to a different method. So remove the range_cont mode which is not used
in the kernel.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
CC: linux-fsdevel@vger.kernel.org
2008-10-14 09:21:02 -04:00
Francois Cami
e1f8e87449 Remove Andrew Morton's old email accounts
People can use the real name an an index into MAINTAINERS to find the
current email address.

Signed-off-by: Francois Cami <francois.cami@free.fr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-10-16 11:21:32 -07:00
Nick Piggin
19fd623127 mm: spinlock tree_lock
mapping->tree_lock has no read lockers.  convert the lock from an rwlock
to a spinlock.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Reviewed-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>
2008-07-26 12:00:06 -07:00
Linus Torvalds
8d2567a620 Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (61 commits)
  ext4: Documention update for new ordered mode and delayed allocation
  ext4: do not set extents feature from the kernel
  ext4: Don't allow nonextenst mount option for large filesystem
  ext4: Enable delalloc by default.
  ext4: delayed allocation i_blocks fix for stat
  ext4: fix delalloc i_disksize early update issue
  ext4: Handle page without buffers in ext4_*_writepage()
  ext4: Add ordered mode support for delalloc
  ext4: Invert lock ordering of page_lock and transaction start in delalloc
  mm: Add range_cont mode for writeback
  ext4: delayed allocation ENOSPC handling
  percpu_counter: new function percpu_counter_sum_and_set
  ext4: Add delayed allocation support in data=writeback mode
  vfs: add hooks for ext4's delayed allocation support
  jbd2: Remove data=ordered mode support using jbd buffer heads
  ext4: Use new framework for data=ordered mode in JBD2
  jbd2: Implement data=ordered mode handling via inodes
  vfs: export filemap_fdatawrite_range()
  ext4: Fix lock inversion in ext4_ext_truncate()
  ext4: Invert the locking order of page_lock and transaction start
  ...
2008-07-15 08:36:38 -07:00
Aneesh Kumar K.V
06d6cf6959 mm: Add range_cont mode for writeback
Filesystems like ext4 needs to start a new transaction in
the writepages for block allocation. This happens with delayed
allocation and there is limit to how many credits we can request
from the journal layer. So we call write_cache_pages multiple
times with wbc->nr_to_write set to the maximum possible value
limitted by the max journal credits available.

Add a new mode to writeback that enables us to handle this
behaviour. In the new mode we update the wbc->range_start
to point to the new offset to be written. Next call to
call to write_cache_pages will start writeout from specified
range_start offset. In the new mode we also limit writing
to the specified wbc->range_end.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2008-07-11 19:27:31 -04:00
Steven Rostedt
3eefae994d ftrace: limit trace entries
Currently there is no protection from the root user to use up all of
memory for trace buffers. If the root user allocates too many entries,
the OOM killer might start kill off all tasks.

This patch adds an algorith to check the following condition:

 pages_requested > (freeable_memory + current_trace_buffer_pages) / 4

If the above is met then the allocation fails. The above prevents more
than 1/4th of freeable memory from being used by trace buffers.

To determine the freeable_memory, I made determine_dirtyable_memory in
mm/page-writeback.c global.

Special thanks goes to Peter Zijlstra for suggesting the above calculation.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 22:05:14 +02:00
Miklos Szeredi
fc3ba692a4 mm: Add NR_WRITEBACK_TEMP counter
Fuse will use temporary buffers to write back dirty data from memory mappings
(normal writes are done synchronously).  This is needed, because there cannot
be any guarantee about the time in which a write will complete.

By using temporary buffers, from the MM's point if view the page is written
back immediately.  If the writeout was due to memory pressure, this
effectively migrates data from a full zone to a less full zone.

This patch adds a new counter (NR_WRITEBACK_TEMP) for the number of pages used
as temporary buffers.

[Lee.Schermerhorn@hp.com: add vmstat_text for NR_WRITEBACK_TEMP]
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 08:29:50 -07:00
Miklos Szeredi
dd5656e59c mm: bdi: export bdi_writeout_inc()
Fuse needs this for writable mmap support.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: 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>
2008-04-30 08:29:50 -07:00
Miklos Szeredi
e4ad08fe64 mm: bdi: add separate writeback accounting capability
Add a new BDI capability flag: BDI_CAP_NO_ACCT_WB.  If this flag is
set, then don't update the per-bdi writeback stats from
test_set_page_writeback() and test_clear_page_writeback().

Misc cleanups:

 - convert bdi_cap_writeback_dirty() and friends to static inline functions
 - create a flag that includes all three dirty/writeback related flags,
   since almst all users will want to have them toghether

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: 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>
2008-04-30 08:29:50 -07:00
Peter Zijlstra
a42dde0415 mm: bdi: allow setting a maximum for the bdi dirty limit
Add "max_ratio" to /sys/class/bdi.  This indicates the maximum percentage of
the global dirty threshold allocated to this bdi.

[mszeredi@suse.cz]

 - fix parsing in max_ratio_store().
 - export bdi_set_max_ratio() to modules
 - limit bdi_dirty with bdi->max_ratio
 - document new sysfs attribute

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 08:29:50 -07:00
Peter Zijlstra
189d3c4a94 mm: bdi: allow setting a minimum for the bdi dirty limit
Under normal circumstances each device is given a part of the total write-back
cache that relates to its current avg writeout speed in relation to the other
devices.

min_ratio - allows one to assign a minimum portion of the write-back cache to
a particular device.  This is useful in situations where you might want to
provide a minimum QoS.  (One request for this feature came from flash based
storage people who wanted to avoid writing out at all costs - they of course
needed some pdflush hacks as well)

max_ratio - allows one to assign a maximum portion of the dirty limit to a
particular device.  This is useful in situations where you want to avoid one
device taking all or most of the write-back cache.  Eg.  an NFS mount that is
prone to get stuck, or a FUSE mount which you don't trust to play fair.

Add "min_ratio" to /sys/class/bdi.  This indicates the minimum percentage of
the global dirty threshold allocated to this bdi.

[mszeredi@suse.cz]

 - fix parsing in min_ratio_store()
 - document new sysfs attribute

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 08:29:50 -07:00
Peter Zijlstra
cf0ca9fe5d mm: bdi: export BDI attributes in sysfs
Provide a place in sysfs (/sys/class/bdi) for the backing_dev_info object.
This allows us to see and set the various BDI specific variables.

In particular this properly exposes the read-ahead window for all relevant
users and /sys/block/<block>/queue/read_ahead_kb should be deprecated.

With patient help from Kay Sievers and Greg KH

[mszeredi@suse.cz]

 - split off NFS and FUSE changes into separate patches
 - document new sysfs attributes under Documentation/ABI
 - do bdi_class_init as a core_initcall, otherwise the "default" BDI
   won't be initialized
 - remove bdi_init_fmt macro, it's not used very much

[akpm@linux-foundation.org: fix ia64 warning]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Greg KH <greg@kroah.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 08:29:49 -07:00
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
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
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
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
Linus Torvalds
c23f72cae9 Revert "writeback: introduce writeback_control.more_io to indicate more io"
This reverts commit 2e6883bdf4, as
requested by Fengguang Wu.  It's not quite fully baked yet, and while
there are patches around to fix the problems it caused, they should get
more testing.  Says Fengguang: "I'll resend them both for -mm later on,
in a more complete patchset".

See

	http://bugzilla.kernel.org/show_bug.cgi?id=9738

for some of this discussion.

Requested-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-01-14 21:21:29 -08:00
Linus Torvalds
8c0863403f dirty page balancing: Get rid of broken unmapped_ratio logic
This code harks back to the days when we didn't count dirty mapped
pages, which led us to try to balance the number of dirty unmapped pages
by how much unmapped memory there was in the system.

That makes no sense any more, since now the dirty counts include the
mapped pages.  Not to mention that the math doesn't work with HIGHMEM
machines anyway, and causes the unmapped_ratio to potentially turn
negative (which we do catch thanks to clamping it at a minimum value,
but I mention that as an indication of how broken the code is).

The code also was written at a time when the default dirty ratio was
much larger, and the unmapped_ratio logic effectively capped that large
dirty ratio a bit.  Again, we've since lowered the dirty ratio rather
aggressively, further lessening the point of that code.

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-11-15 16:41:52 -08:00
Peter Zijlstra
5fce25a9df mm: speed up writeback ramp-up on clean systems
We allow violation of bdi limits if there is a lot of room on the system.
Once we hit half the total limit we start enforcing bdi limits and bdi
ramp-up should happen.  Doing it this way avoids many small writeouts on an
otherwise idle system and should also speed up the ramp-up.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-11-14 18:45:38 -08:00
Simon Arlott
183ff22bb6 spelling fixes: mm/
Spelling fixes in mm/.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
2007-10-20 01:27:18 +02:00
Fengguang Wu
369f2389e7 writeback: remove unnecessary wait in throttle_vm_writeout()
We don't want to introduce pointless delays in throttle_vm_writeout() when
the writeback limits are not yet exceeded, do we?

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: Greg KH <greg@kroah.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:43:02 -07:00
Joern Engel
1c0eeaf569 introduce I_SYNC
I_LOCK was used for several unrelated purposes, which caused deadlock
situations in certain filesystems as a side effect.  One of the purposes
now uses the new I_SYNC bit.

Also document the various bits and change their order from historical to
logical.

[bunk@stusta.de: make fs/inode.c:wake_up_inode() static]
Signed-off-by: Joern Engel <joern@wohnheim.fh-wedel.de>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:43:02 -07:00
Fengguang Wu
2e6883bdf4 writeback: introduce writeback_control.more_io to indicate more io
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 this situation.  With it the big
dirty file no longer has to wait for the next kupdate invocation 5s later.

Cc: David Chinner <dgc@sgi.com>
Cc: Ken Chen <kenchen@google.com>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:43:02 -07:00
Andrew Morton
e423003028 writeback: don't propagate AOP_WRITEPAGE_ACTIVATE
This is a writeback-internal marker but we're propagating it all the way back
to userspace!.

Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:42:46 -07:00
Peter Zijlstra
3e26c149c3 mm: dirty balancing for tasks
Based on ideas of Andrew:
  http://marc.info/?l=linux-kernel&m=102912915020543&w=2

Scale the bdi dirty limit inversly with the tasks dirty rate.
This makes heavy writers have a lower dirty limit than the occasional writer.

Andrea proposed something similar:
  http://lwn.net/Articles/152277/

The main disadvantage to his patch is that he uses an unrelated quantity to
measure time, which leaves him with a workload dependant tunable. Other than
that the two approaches appear quite similar.

[akpm@linux-foundation.org: fix warning]
Signed-off-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>
2007-10-17 08:42:45 -07:00
Peter Zijlstra
04fbfdc14e mm: per device dirty threshold
Scale writeback cache per backing device, proportional to its writeout speed.

By decoupling the BDI dirty thresholds a number of problems we currently have
will go away, namely:

 - mutual interference starvation (for any number of BDIs);
 - deadlocks with stacked BDIs (loop, FUSE and local NFS mounts).

It might be that all dirty pages are for a single BDI while other BDIs are
idling. By giving each BDI a 'fair' share of the dirty limit, each one can have
dirty pages outstanding and make progress.

A global threshold also creates a deadlock for stacked BDIs; when A writes to
B, and A generates enough dirty pages to get throttled, B will never start
writeback until the dirty pages go away. Again, by giving each BDI its own
'independent' dirty limit, this problem is avoided.

So the problem is to determine how to distribute the total dirty limit across
the BDIs fairly and efficiently. A DBI that has a large dirty limit but does
not have any dirty pages outstanding is a waste.

What is done is to keep a floating proportion between the DBIs based on
writeback completions. This way faster/more active devices get a larger share
than slower/idle devices.

[akpm@linux-foundation.org: fix warnings]
[hugh@veritas.com: Fix occasional hang when a task couldn't get out of balance_dirty_pages]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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>
2007-10-17 08:42:45 -07:00
Peter Zijlstra
69cb51d18c mm: count writeback pages per BDI
Count per BDI writeback pages.

Signed-off-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>
2007-10-17 08:42:45 -07:00
Peter Zijlstra
c9e51e4180 mm: count reclaimable pages per BDI
Count per BDI reclaimable pages; nr_reclaimable = nr_dirty + nr_unstable.

Signed-off-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>
2007-10-17 08:42:45 -07:00
Lee Schermerhorn
37b07e4163 memoryless nodes: fixup uses of node_online_map in generic code
Here's a cut at fixing up uses of the online node map in generic code.

mm/shmem.c:shmem_parse_mpol()

	Ensure nodelist is subset of nodes with memory.
	Use node_states[N_HIGH_MEMORY] as default for missing
	nodelist for interleave policy.

mm/shmem.c:shmem_fill_super()

	initialize policy_nodes to node_states[N_HIGH_MEMORY]

mm/page-writeback.c:highmem_dirtyable_memory()

	sum over nodes with memory

mm/page_alloc.c:zlc_setup()

	allowednodes - use nodes with memory.

mm/page_alloc.c:default_zonelist_order()

	average over nodes with memory.

mm/page_alloc.c:find_next_best_node()

	skip nodes w/o memory.
	N_HIGH_MEMORY state mask may not be initialized at this time,
	unless we want to depend on early_calculate_totalpages() [see
	below].  Will ZONE_MOVABLE ever be configurable?

mm/page_alloc.c:find_zone_movable_pfns_for_nodes()

	spread kernelcore over nodes with memory.

	This required calling early_calculate_totalpages()
	unconditionally, and populating N_HIGH_MEMORY node
	state therein from nodes in the early_node_map[].
	If we can depend on this, we can eliminate the
	population of N_HIGH_MEMORY mask from __build_all_zonelists()
	and use the N_HIGH_MEMORY mask in find_next_best_node().

mm/mempolicy.c:mpol_check_policy()

	Ensure nodes specified for policy are subset of
	nodes with memory.

[akpm@linux-foundation.org: fix warnings]
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-16 09:42:59 -07:00
Nick Piggin
0012818810 mm: use lockless radix-tree probe
Probing pages and radix_tree_tagged are lockless operations with the lockless
radix-tree.  Convert these users to RCU locking rather than using tree_lock.

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>
2007-10-16 09:42:53 -07:00
Peter Zijlstra
a200ee182a mm: set_page_dirty_balance() vs ->page_mkwrite()
All the current page_mkwrite() implementations also set the page dirty. Which
results in the set_page_dirty_balance() call to _not_ call balance, because the
page is already found dirty.

This allows us to dirty a _lot_ of pages without ever hitting
balance_dirty_pages().  Not good (tm).

Force a balance call if ->page_mkwrite() was successful.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-08 12:58:14 -07:00
Andrew Morton
d688abf50b move page writeback acounting out of macros
page-writeback accounting is presently performed in the page-flags macros.
This is inconsistent and a bit ugly and makes it awkward to implement
per-backing_dev under-writeback page accounting.

So move this accounting down to the callsite(s).

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>
2007-07-19 10:04:52 -07:00
Fengguang Wu
fe3cba17c4 mm: share PG_readahead and PG_reclaim
Share the same page flag bit for PG_readahead and PG_reclaim.

One is used only on file reads, another is only for emergency writes.  One
is used mostly for fresh/young pages, another is for old pages.

Combinations of possible interactions are:

a) clear PG_reclaim => implicit clear of PG_readahead
	it will delay an asynchronous readahead into a synchronous one
	it actually does _good_ for readahead:
		the pages will be reclaimed soon, it's readahead thrashing!
		in this case, synchronous readahead makes more sense.

b) clear PG_readahead => implicit clear of PG_reclaim
	one(and only one) page will not be reclaimed in time
	it can be avoided by checking PageWriteback(page) in readahead first

c) set PG_reclaim => implicit set of PG_readahead
	will confuse readahead and make it restart the size rampup process
	it's a trivial problem, and can mostly be avoided by checking
	PageWriteback(page) first in readahead

d) set PG_readahead => implicit set of PG_reclaim
	PG_readahead will never be set on already cached pages.
	PG_reclaim will always be cleared on dirtying a page.
	so not a problem.

In summary,
	a)   we get better behavior
	b,d) possible interactions can be avoided
	c)   racy condition exists that might affect readahead, but the chance
	     is _really_ low, and the hurt on readahead is trivial.

Compound pages also use PG_reclaim, but for now they do not interact with
reclaim/readahead code.

Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19 10:04:44 -07:00
Nick Piggin
79352894b2 mm: fix clear_page_dirty_for_io vs fault race
Fix msync data loss and (less importantly) dirty page accounting
inaccuracies due to the race remaining in clear_page_dirty_for_io().

The deleted comment explains what the race was, and the added comments
explain how it is fixed.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19 10:04:41 -07:00
Nick Piggin
787d2214c1 fs: introduce some page/buffer invariants
It is a bug to set a page dirty if it is not uptodate unless it has
buffers.  If the page has buffers, then the page may be dirty (some buffers
dirty) but not uptodate (some buffers not uptodate).  The exception to this
rule is if the set_page_dirty caller is racing with truncate or invalidate.

A buffer can not be set dirty if it is not uptodate.

If either of these situations occurs, it indicates there could be some data
loss problem.  Some of these warnings could be a harmless one where the
page or buffer is set uptodate immediately after it is dirtied, however we
should fix those up, and enforce this ordering.

Bring the order of operations for truncate into line with those of
invalidate.  This will prevent a page from being able to go !uptodate while
we're holding the tree_lock, which is probably a good thing anyway.

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>
2007-07-17 10:23:02 -07:00
Andrew Morton
3e733f071e dirty_writeback_centisecs_handler() cleanup
Repair indenting bustage.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 09:05:47 -07:00
Miklos Szeredi
0ea9718016 consolidate generic_writepages and mpage_writepages
Clean up massive code duplication between mpage_writepages() and
generic_writepages().

The new generic function, write_cache_pages() takes a function pointer
argument, which will be called for each page to be written.

Maybe cifs_writepages() too can use this infrastructure, but I'm not
touching that with a ten-foot pole.

The upcoming page writeback support in fuse will also want this.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11 08:29:35 -07:00
Guillaume Chazarain
3e9f45bd18 Factor outstanding I/O error handling
Cleanup: setting an outstanding error on a mapping was open coded too many
times.  Factor it out in mapping_set_error().

Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08 11:14:57 -07:00