Commit Graph

18 Commits

Author SHA1 Message Date
Jiaying Zhang 8c0bec2151 ext4: remove i_mutex lock in ext4_evict_inode to fix lockdep complaining
The i_mutex lock and flush_completed_IO() added by commit 2581fdc810
in ext4_evict_inode() causes lockdep complaining about potential
deadlock in several places.  In most/all of these LOCKDEP complaints
it looks like it's a false positive, since many of the potential
circular locking cases can't take place by the time the
ext4_evict_inode() is called; but since at the very least it may mask
real problems, we need to address this.

This change removes the flush_completed_IO() and i_mutex lock in
ext4_evict_inode().  Instead, we take a different approach to resolve
the software lockup that commit 2581fdc810 intends to fix.  Rather
than having ext4-dio-unwritten thread wait for grabing the i_mutex
lock of an inode, we use mutex_trylock() instead, and simply requeue
the work item if we fail to grab the inode's i_mutex lock.

This should speed up work queue processing in general and also
prevents the following deadlock scenario: During page fault,
shrink_icache_memory is called that in turn evicts another inode B.
Inode B has some pending io_end work so it calls ext4_ioend_wait()
that waits for inode B's i_ioend_count to become zero.  However, inode
B's ioend work was queued behind some of inode A's ioend work on the
same cpu's ext4-dio-unwritten workqueue.  As the ext4-dio-unwritten
thread on that cpu is processing inode A's ioend work, it tries to
grab inode A's i_mutex lock.  Since the i_mutex lock of inode A is
still hold before the page fault happened, we enter a deadlock.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-08-31 11:50:51 -04:00
Tao Ma 32c80b32c0 ext4: Resolve the hang of direct i/o read in handling EXT4_IO_END_UNWRITTEN.
EXT4_IO_END_UNWRITTEN flag set and the increase of i_aiodio_unwritten
should be done simultaneously since ext4_end_io_nolock always clear
the flag and decrease the counter in the same time.

We don't increase i_aiodio_unwritten when setting
EXT4_IO_END_UNWRITTEN so it will go nagative and causes some process
to wait forever.

Part of the patch came from Eric in his e-mail, but it doesn't fix the
problem met by Michael actually.

http://marc.info/?l=linux-ext4&m=131316851417460&w=2

Reported-and-Tested-by: Michael Tokarev<mjt@tls.msk.ru>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
2011-08-13 12:30:59 -04:00
Theodore Ts'o 275d3ba6b4 ext4: remove loop around bio_alloc()
These days, bio_alloc() is guaranteed to never fail (as long as nvecs
is less than BIO_MAX_PAGES), so we don't need the loop around the
struct bio allocation.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-06-29 21:44:45 -04:00
Curt Wohlgemuth 39db00f1c4 ext4: don't set PageUptodate in ext4_end_bio()
In the bio completion routine, we should not be setting
PageUptodate at all -- it's set at sys_write() time, and is
unaffected by success/failure of the write to disk.

This can cause a page corruption bug when the file system's
block size is less than the architecture's VM page size.

if we have only written a single block -- we might end up
setting the page's PageUptodate flag, indicating that page
is completely read into memory, which may not be true.
This could cause subsequent reads to get bad data.

This commit also takes the opportunity to clean up error
handling in ext4_end_bio(), and remove some extraneous code:

   - fixes ext4_end_bio() to set AS_EIO in the
     page->mapping->flags on error, which was left out by
     mistake.  This is needed so that fsync() will
     return an error if there was an I/O error.
   - remove the clear_buffer_dirty() call on unmapped
     buffers for each page.
   - consolidate page/buffer error handling in a single
     section.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Jim Meyering <jim@meyering.net>
Reported-by: Hugh Dickins <hughd@google.com>
Cc: Mingming Cao <cmm@us.ibm.com>
2011-04-30 13:26:26 -04:00
Linus Torvalds ae005cbed1 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: (43 commits)
  ext4: fix a BUG in mb_mark_used during trim.
  ext4: unused variables cleanup in fs/ext4/extents.c
  ext4: remove redundant set_buffer_mapped() in ext4_da_get_block_prep()
  ext4: add more tracepoints and use dev_t in the trace buffer
  ext4: don't kfree uninitialized s_group_info members
  ext4: add missing space in printk's in __ext4_grp_locked_error()
  ext4: add FITRIM to compat_ioctl.
  ext4: handle errors in ext4_clear_blocks()
  ext4: unify the ext4_handle_release_buffer() api
  ext4: handle errors in ext4_rename
  jbd2: add COW fields to struct jbd2_journal_handle
  jbd2: add the b_cow_tid field to journal_head struct
  ext4: Initialize fsync transaction ids in ext4_new_inode()
  ext4: Use single thread to perform DIO unwritten convertion
  ext4: optimize ext4_bio_write_page() when no extent conversion is needed
  ext4: skip orphan cleanup if fs has unknown ROCOMPAT features
  ext4: use the nblocks arg to ext4_truncate_restart_trans()
  ext4: fix missing iput of root inode for some mount error paths
  ext4: make FIEMAP and delayed allocation play well together
  ext4: suppress verbose debugging information if malloc-debug is off
  ...

Fi up conflicts in fs/ext4/super.c due to workqueue changes
2011-03-25 09:57:41 -07:00
Jens Axboe 721a9602e6 block: kill off REQ_UNPLUG
With the plugging now being explicitly controlled by the
submitter, callers need not pass down unplugging hints
to the block layer. If they want to unplug, it's because they
manually plugged on their own - in which case, they should just
unplug at will.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-03-10 08:52:27 +01:00
Theodore Ts'o b616844310 ext4: optimize ext4_bio_write_page() when no extent conversion is needed
If no extent conversion is required, wake up any processes waiting for
the page's writeback to be complete and free the ext4_io_end structure
directly in ext4_end_bio() instead of dropping it on the linked list
(which requires taking a spinlock to queue and dequeue the io_end
structure), and waiting for the workqueue to do this work.

This removes an extra scheduling delay before process waiting for an
fsync() to complete gets woken up, and it also reduces the CPU
overhead for a random write workload.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-02-28 13:12:38 -05:00
Theodore Ts'o a54aa76108 ext4: don't leave PageWriteback set after memory failure
In ext4_bio_write_page(), if the memory allocation for the struct
ext4_io_page fails, it returns with the page's PageWriteback flag set.
This will end up causing the page not to skip writeback in
WB_SYNC_NONE mode, and in WB_SYNC_ALL mode (i.e., on a sync, fsync, or
umount) the writeback daemon will get stuck forever on the
wait_on_page_writeback() function in write_cache_pages_da().

Or, if journalling is enabled and the file gets deleted, it the
journal thread can get stuck in journal_finish_inode_data_buffers()
call to filemap_fdatawait().

Another place where things can get hung up is in
truncate_inode_pages(), called out of ext4_evict_inode().

Fix this by not setting PageWriteback until after we have successfully
allocated the struct ext4_io_page.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-02-27 16:43:24 -05:00
Peter Huewe 7dc576158d ext4: Fix sparse warning: Using plain integer as NULL pointer
This patch fixes the warning "Using plain integer as NULL pointer",
generated by sparse, by replacing the offending 0s with NULL.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-02-21 21:01:42 -05:00
Eric Sandeen e9e3bcecf4 ext4: serialize unaligned asynchronous DIO
ext4 has a data corruption case when doing non-block-aligned
asynchronous direct IO into a sparse file, as demonstrated
by xfstest 240.

The root cause is that while ext4 preallocates space in the
hole, mappings of that space still look "new" and 
dio_zero_block() will zero out the unwritten portions.  When
more than one AIO thread is going, they both find this "new"
block and race to zero out their portion; this is uncoordinated
and causes data corruption.

Dave Chinner fixed this for xfs by simply serializing all
unaligned asynchronous direct IO.  I've done the same here.
The difference is that we only wait on conversions, not all IO.
This is a very big hammer, and I'm not very pleased with
stuffing this into ext4_file_write().  But since ext4 is
DIO_LOCKING, we need to serialize it at this high level.

I tried to move this into ext4_ext_direct_IO, but by then
we have the i_mutex already, and we will wait on the
work queue to do conversions - which must also take the
i_mutex.  So that won't work.

This was originally exposed by qemu-kvm installing to
a raw disk image with a normal sector-63 alignment.  I've
tested a backport of this patch with qemu, and it does
avoid the corruption.  It is also quite a lot slower
(14 min for package installs, vs. 8 min for well-aligned)
but I'll take slow correctness over fast corruption any day.

Mingming suggested that we can track outstanding
conversions, and wait on those so that non-sparse
files won't be affected, and I've implemented that here;
unaligned AIO to nonsparse files won't take a perf hit.

[tytso@mit.edu: Keep the mutex as a hashed array instead
 of bloating the ext4 inode]

[tytso@mit.edu: Fix up namespace issues so that global
 variables are protected with an "ext4_" prefix.]

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-02-12 08:17:34 -05:00
Curt Wohlgemuth d50bdd5aa5 ext4: Fix data corruption with multi-block writepages support
This fixes a corruption problem with the multi-block
writepages submittal change for ext4, from commit
bd2d0210cf ("ext4: use bio
layer instead of buffer layer in mpage_da_submit_io").

(Note that this corruption is not present in 2.6.37 on
ext4, because the corruption was detected after the
feature was merged in 2.6.37-rc1, and so it was turned
off by adding a non-default mount option,
mblk_io_submit.  With this commit, which hopefully
fixes the last of the bugs with this feature, we'll be
able to turn on this performance feature by default in
2.6.38, and remove the mblk_io_submit option.)

The ext4 code path to bundle multiple pages for
writeback in ext4_bio_write_page() had a bug: we should
be clearing buffer head dirty flags *before* we submit
the bio, not in the completion routine.

The patch below was tested on 2.6.37 under KVM with the
postgresql script which was submitted by Jon Nelson as
documented in commit 1449032be1.

Without the patch, I'd hit the corruption problem about
50-70% of the time.  With the patch, I executed the
script > 100 times with no corruption seen.

I also fixed a bug to make sure ext4_end_bio() doesn't
dereference the bio after the bio_put() call.

Reported-by: Jon Nelson <jnelson@jamponi.net>
Reported-by: Matthias Bayer <jackdachef@gmail.com>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
2011-02-07 12:46:14 -05:00
Dan Carpenter 13195184a8 ext4: test the correct variable in ext4_init_pageio()
This is a copy and paste error.  The intent was to check
"io_page_cachep".  We tested "io_page_cachep" earlier.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-01-10 12:10:44 -05:00
Jesper Juhl b17b35ec13 ext4: use kmem_cache_zalloc() in ext4_init_io_end()
Use advantage of kmem_cache_zalloc() to remove a memset() call in
ext4_init_io_end() and save a few bytes.

Before:
 [jj@dragon linux-2.6]$ size fs/ext4/page-io.o
    text    data     bss     dec     hex filename
    3016       0     624    3640     e38 fs/ext4/page-io.o
After:
 [jj@dragon linux-2.6]$ size fs/ext4/page-io.o
    text    data     bss     dec     hex filename
    3000       0     624    3624     e28 fs/ext4/page-io.o

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-12-19 21:41:55 -05:00
Markus Trippelsdorf 08da1193d2 ext4: fix setting random pages PageUptodate
ext4_end_bio calls put_page and kmem_cache_free before calling
SetPageUpdate(). This can result in setting the PageUptodate bit on
random pages and causes the following BUG:

 BUG: Bad page state in process rm  pfn:52e54
 page:ffffea0001222260 count:0 mapcount:0 mapping:          (null) index:0x0
 arch kernel: page flags: 0x4000000000000008(uptodate)

Fix the problem by moving put_io_page() after the SetPageUpdate() call.

Thanks to Hugh Dickins for analyzing this problem.

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-17 21:46:06 -05:00
Theodore Ts'o 83668e7141 ext4: fix potential race when freeing ext4_io_page structures
Use an atomic_t and make sure we don't free the structure while we
might still be submitting I/O for that page.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-08 13:45:33 -05:00
Theodore Ts'o f7ad6d2e92 ext4: handle writeback of inodes which are being freed
The following BUG can occur when an inode which is getting freed when
it still has dirty pages outstanding, and it gets deleted (in this
because it was the target of a rename).  In ordered mode, we need to
make sure the data pages are written just in case we crash before the
rename (or unlink) is committed.  If the inode is being freed then
when we try to igrab the inode, we end up tripping the BUG_ON at
fs/ext4/page-io.c:146.

To solve this problem, we need to keep track of the number of io
callbacks which are pending, and avoid destroying the inode until they
have all been completed.  That way we don't have to bump the inode
count to keep the inode from being destroyed; an approach which
doesn't work because the count could have already been dropped down to
zero before the inode writeback has started (at which point we're not
allowed to bump the count back up to 1, since it's already started
getting freed).

Thanks to Dave Chinner for suggesting this approach, which is also
used by XFS.

  kernel BUG at /scratch_space/linux-2.6/fs/ext4/page-io.c:146!
  Call Trace:
   [<ffffffff811075b1>] ext4_bio_write_page+0x172/0x307
   [<ffffffff811033a7>] mpage_da_submit_io+0x2f9/0x37b
   [<ffffffff811068d7>] mpage_da_map_and_submit+0x2cc/0x2e2
   [<ffffffff811069b3>] mpage_add_bh_to_extent+0xc6/0xd5
   [<ffffffff81106c66>] write_cache_pages_da+0x2a4/0x3ac
   [<ffffffff81107044>] ext4_da_writepages+0x2d6/0x44d
   [<ffffffff81087910>] do_writepages+0x1c/0x25
   [<ffffffff810810a4>] __filemap_fdatawrite_range+0x4b/0x4d
   [<ffffffff810815f5>] filemap_fdatawrite_range+0xe/0x10
   [<ffffffff81122a2e>] jbd2_journal_begin_ordered_truncate+0x7b/0xa2
   [<ffffffff8110615d>] ext4_evict_inode+0x57/0x24c
   [<ffffffff810c14a3>] evict+0x22/0x92
   [<ffffffff810c1a3d>] iput+0x212/0x249
   [<ffffffff810bdf16>] dentry_iput+0xa1/0xb9
   [<ffffffff810bdf6b>] d_kill+0x3d/0x5d
   [<ffffffff810be613>] dput+0x13a/0x147
   [<ffffffff810b990d>] sys_renameat+0x1b5/0x258
   [<ffffffff81145f71>] ? _atomic_dec_and_lock+0x2d/0x4c
   [<ffffffff810b2950>] ? cp_new_stat+0xde/0xea
   [<ffffffff810b29c1>] ? sys_newlstat+0x2d/0x38
   [<ffffffff810b99c6>] sys_rename+0x16/0x18
   [<ffffffff81002a2b>] system_call_fastpath+0x16/0x1b

Reported-by: Nick Bowler <nbowler@elliptictech.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Tested-by: Nick Bowler <nbowler@elliptictech.com>
2010-11-08 13:43:33 -05:00
Theodore Ts'o 5dabfc78dc ext4: rename {exit,init}_ext4_*() to ext4_{exit,init}_*()
This is a cleanup to avoid namespace leaks out of fs/ext4

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o bd2d0210cf ext4: use bio layer instead of buffer layer in mpage_da_submit_io
Call the block I/O layer directly instad of going through the buffer
layer.  This should give us much better performance and scalability,
as well as lowering our CPU utilization when doing buffered writeback.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:10 -04:00