linux-toradex.git/mm/page-writeback.c, branch v2.6.27.14

mm: write_cache_pages more terminate quickly

2009-01-25T00:36:27+00:00

commit 82fd1a9a8ced9607312b54859572bcc6211e8919 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages terminate quickly

2009-01-25T00:36:27+00:00

commit d5482cdf8a0aacb1e6468a97d5544f5829c8d8c4 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages optimise page cleaning

2009-01-25T00:36:27+00:00

commit 515f4a037fb9ab736f8bad733fcd2ffd350cf265 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages cleanups

2009-01-25T00:36:26+00:00

commit 5a3d5c9813db56a75934eb1015367fda23a8b0b4 upstream.

Get rid of some complex expressions from flow control statements, add a
comment, remove some duplicate code.

Signed-off-by: Nick Piggin 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages integrity fix

2009-01-25T00:36:26+00:00

commit 05fe478dd04e02fa230c305ab9b5616669821dd3 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages writepage error fix

2009-01-25T00:36:26+00:00

commit 00266770b8b3a6a77f896ca501a0613739086832 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages early loop termination

2009-01-25T00:36:26+00:00

commit bd19e012f6fd3b7309689165ea865cbb7bb88c1e upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: write_cache_pages cyclic fix

2009-01-25T00:36:26+00:00

commit 31a12666d8f0c22235297e1c1575f82061480029 upstream.

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 
Cc: Chris Mason 
Cc: Dave Chinner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: spinlock tree_lock

2008-07-26T19:00:06+00:00

mapping->tree_lock has no read lockers.  convert the lock from an rwlock
to a spinlock.

Signed-off-by: Nick Piggin 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Hugh Dickins 
Cc: "Paul E. McKenney" 
Reviewed-by: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2008-07-15T15:36:38+00:00

* '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
  ...