The following race is possible between start_this_handle() and someone
calling jbd2_journal_flush().
Process A Process B
start_this_handle().
if (journal->j_barrier_count) # false
if (!journal->j_running_transaction) { #true
read_unlock(&journal->j_state_lock);
jbd2_journal_lock_updates()
jbd2_journal_flush()
write_lock(&journal->j_state_lock);
if (journal->j_running_transaction) {
# false
... wait for committing trans ...
write_unlock(&journal->j_state_lock);
...
write_lock(&journal->j_state_lock);
if (!journal->j_running_transaction) { # true
jbd2_get_transaction(journal, new_transaction);
write_unlock(&journal->j_state_lock);
goto repeat; # eventually blocks on j_barrier_count > 0
...
J_ASSERT(!journal->j_running_transaction);
# fails
We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
in exclusive mode.
Reported-by: yjwsignal@empal.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
ext4_handle_release_buffer() was intended to remove journal
write access from a buffer, but it doesn't actually do anything
at all other than add a BUFFER_TRACE point, but it's not reliably
used for that either. Remove all the associated dead code.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
ext4 users of data=journal mode with blocksize < pagesize were
occasionally hitting assertion failure in
jbd2_journal_commit_transaction() checking whether the transaction has
at least as many credits reserved as buffers attached. The core of the
problem is that when a file gets truncated, buffers that still need
checkpointing or that are attached to the committing transaction are
left with buffer_mapped set. When this happens to buffers beyond i_size
attached to a page stradding i_size, subsequent write extending the file
will see these buffers and as they are mapped (but underlying blocks
were freed) things go awry from here.
The assertion failure just coincidentally (and in this case luckily as
we would start corrupting filesystem) triggers due to journal_head not
being properly cleaned up as well.
We fix the problem by unmapping buffers if possible (in lots of cases we
just need a buffer attached to a transaction as a place holder but it
must not be written out anyway). And in one case, we just have to bite
the bullet and wait for transaction commit to finish.
CC: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Use kmem_cache_zalloc wrapper instead of flag __GFP_ZERO.
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
The check b_jlist == BJ_None in __journal_try_to_free_buffer() is
always true (__jbd2_journal_temp_unlink_buffer() also checks this in
an assertion) so just remove it.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
There is normally only a handful of these active at any one time, but
putting them in a separate slab cache makes debugging memory
corruption problems easier. Manish Katiyar also wanted this make it
easier to test memory failure scenarios in the jbd2 layer.
Cc: Manish Katiyar <mkatiyar@gmail.com>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
journal_unmap_buffer()'s zap_buffer: code clears a lot of buffer head
state ala discard_buffer(), but does not touch _Delay or _Unwritten as
discard_buffer() does.
This can be problematic in some areas of the ext4 code which assume
that if they have found a buffer marked unwritten or delay, then it's
a live one. Perhaps those spots should check whether it is mapped
as well, but if jbd2 is going to tear down a buffer, let's really
tear it down completely.
Without this I get some fsx failures on sub-page-block filesystems
up until v3.2, at which point 4e96b2dbbf
and 189e868fa8 make the failures go
away, because buried within that large change is some more flag
clearing. I still think it's worth doing in jbd2, since
->invalidatepage leads here directly, and it's the right place
to clear away these flags.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
Toshiyuki Okajima found out that when running
for ((i=0; i < 100000; i++)); do
if ((i%2 == 0)); then
chattr +j /mnt/file
else
chattr -j /mnt/file
fi
echo "0" >> /mnt/file
done
process sometimes hangs indefinitely in jbd2_journal_lock_updates().
Toshiyuki identified that the following race happens:
jbd2_journal_lock_updates() |jbd2_journal_stop()
---------------------------------------+---------------------------------------
write_lock(&journal->j_state_lock) | .
++journal->j_barrier_count | .
spin_lock(&tran->t_handle_lock) | .
atomic_read(&tran->t_updates) //not 0 |
| atomic_dec_and_test(&tran->t_updates)
| // t_updates = 0
| wake_up(&journal->j_wait_updates)
prepare_to_wait() | // no process is woken up.
spin_unlock(&tran->t_handle_lock) |
write_unlock(&journal->j_state_lock) |
schedule() // never return |
We fix the problem by first calling prepare_to_wait() and only after that
checking t_updates in jbd2_journal_lock_updates().
Reported-and-analyzed-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Some jbd2 code prints out kernel messages with "JBD2: " prefix, at the
same time other jbd2 code prints with "JBD: " prefix. Unify the prefix
to "JBD2: ".
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Fix build error when CONFIG_BUG is not enabled:
fs/jbd2/transaction.c:1175:3: error: implicit declaration of function '__WARN'
by changing __WARN() to WARN_ON(), as suggested by
Arnaud Lacombe <lacombar@gmail.com>.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Arnaud Lacombe <lacombar@gmail.com>
This silences some Sparse warnings:
fs/jbd2/transaction.c:135:69: warning: incorrect type in argument 2 (different base types)
fs/jbd2/transaction.c:135:69: expected restricted gfp_t [usertype] flags
fs/jbd2/transaction.c:135:69: got int [signed] gfp_mask
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Add debugging information in case jbd2_journal_dirty_metadata() is
called with a buffer_head which didn't have
jbd2_journal_get_write_access() called on it, or if the journal_head
has the wrong transaction in it. In addition, return an error code.
This won't change anything for ocfs2, which will BUG_ON() the non-zero
exit code.
For ext4, the caller of this function is ext4_handle_dirty_metadata(),
and on seeing a non-zero return code, will call __ext4_journal_stop(),
which will print the function and line number of the (buggy) calling
function and abort the journal. This will allow us to recover instead
of bug halting, which is better from a robustness and reliability
point of view.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
jbd2_journal_remove_journal_head() can oops when trying to access
journal_head returned by bh2jh(). This is caused for example by the
following race:
TASK1 TASK2
jbd2_journal_commit_transaction()
...
processing t_forget list
__jbd2_journal_refile_buffer(jh);
if (!jh->b_transaction) {
jbd_unlock_bh_state(bh);
jbd2_journal_try_to_free_buffers()
jbd2_journal_grab_journal_head(bh)
jbd_lock_bh_state(bh)
__journal_try_to_free_buffer()
jbd2_journal_put_journal_head(jh)
jbd2_journal_remove_journal_head(bh);
jbd2_journal_put_journal_head() in TASK2 sees that b_jcount == 0 and
buffer is not part of any transaction and thus frees journal_head
before TASK1 gets to doing so. Note that even buffer_head can be
released by try_to_free_buffers() after
jbd2_journal_put_journal_head() which adds even larger opportunity for
oops (but I didn't see this happen in reality).
Fix the problem by making transactions hold their own journal_head
reference (in b_jcount). That way we don't have to remove journal_head
explicitely via jbd2_journal_remove_journal_head() and instead just
remove journal_head when b_jcount drops to zero. The result of this is
that [__]jbd2_journal_refile_buffer(),
[__]jbd2_journal_unfile_buffer(), and
__jdb2_journal_remove_checkpoint() can free journal_head which needs
modification of a few callers. Also we have to be careful because once
journal_head is removed, buffer_head might be freed as well. So we
have to get our own buffer_head reference where it matters.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
credits isn't a parameter for jbd2_journal_get_write_access and
jbd2_journal_get_undo_access. So remove the corresponding comments.
Acked-by: Jan Kara <jack@suse.cz>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
jbd2__journal_start() returns an ERR_PTR() value rather than NULL on
failure.
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
In data=ordered mode, it's theoretically possible (however rare) that
an inode is filed to transaction's t_inode_list and a flusher thread
writes all the data and inode is reclaimed before the transaction
starts to commit. In such a case, we could erroneously omit sending a
flush to file system device when it is different from the journal
device (because data can still be in disk cache only).
Fix the problem by setting a flag in a transaction when some inode is added
to it and then send disk flush in the commit code when the flag is set.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
t_max_wait is added in commit 8e85fb3f to indicate how long we
were waiting for new transaction to start. In commit 6d0bf005,
it is moved to another function named update_t_max_wait to
avoid a build warning. But the wrong thing is that the original
'ts' is initialized in the start of function start_this_handle
and we can calculate t_max_wait in the right way. while with
this change, ts is initialized within the function and t_max_wait
can never be calculated right.
This patch moves the initialization of ts to the original beginning
of start_this_handle and pass it to function update_t_max_wait so
that it can be calculated right and the build warning is avoided also.
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
On an SMP ARM system running ext4, I've received a report that the
first J_ASSERT in jbd2_journal_commit_transaction has been triggering:
J_ASSERT(journal->j_running_transaction != NULL);
While investigating possible causes for this problem, I noticed that
__jbd2_log_start_commit() is getting called with j_state_lock only
read-locked, in spite of the fact that it's possible for it might
j_commit_request. Fix this by grabbing the necessary information so
we can test to see if we need to start a new transaction before
dropping the read lock, and then calling jbd2_log_start_commit() which
will grab the write lock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
'buffer_head' should be 'journal_head'
This is a port of a patch which Namhyung Kim <namhyung@gmail.com> made
to fs/jbd to jbd2.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
An attempt to modify the file system during the call to
jbd2_destroy_journal() can lead to a system lockup. So add some
checking to make it much more obvious when this happens to and to
determine where the offending code is located.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This should remove the last exclusive lock from start_this_handle(),
so that we should now be able to start multiple transactions at the
same time on large SMP systems.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Lockstat reports have shown that j_state_lock is a major source of
lock contention, especially on systems with more than 4 CPU cores. So
change it to be a read/write spinlock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
By using an atomic_t for t_updates and t_outstanding credits, this
should allow us to not need to take transaction t_handle_lock in
jbd2_journal_stop().
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
__GFP_NOFAIL is going away, so add our own retry loop. Also add
jbd2__journal_start() and jbd2__journal_restart() which take a gfp
mask, so that file systems can optionally (re)start transaction
handles using GFP_KERNEL. If they do this, then they need to be
prepared to handle receiving an PTR_ERR(-ENOMEM) error, and be ready
to reflect that error up to userspace.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
OCFS2 uses t_commit trigger to compute and store checksum of the just
committed blocks. When a buffer has b_frozen_data, checksum is computed
for it instead of b_data but this can result in an old checksum being
written to the filesystem in the following scenario:
1) transaction1 is opened
2) handle1 is opened
3) journal_access(handle1, bh)
- This sets jh->b_transaction to transaction1
4) modify(bh)
5) journal_dirty(handle1, bh)
6) handle1 is closed
7) start committing transaction1, opening transaction2
8) handle2 is opened
9) journal_access(handle2, bh)
- This copies off b_frozen_data to make it safe for transaction1 to commit.
jh->b_next_transaction is set to transaction2.
10) jbd2_journal_write_metadata() checksums b_frozen_data
11) the journal correctly writes b_frozen_data to the disk journal
12) handle2 is closed
- There was no dirty call for the bh on handle2, so it is never queued for
any more journal operation
13) Checkpointing finally happens, and it just spools the bh via normal buffer
writeback. This will write b_data, which was never triggered on and thus
contains a wrong (old) checksum.
This patch fixes the problem by calling the trigger at the moment data is
frozen for journal commit - i.e., either when b_frozen_data is created by
do_get_write_access or just before we write a buffer to the log if
b_frozen_data does not exist. We also rename the trigger to t_frozen as
that better describes when it is called.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
One of the most contended locks in the jbd2 layer is j_state_lock when
running dbench. This is especially true if using the real-time kernel
with its "sleeping spinlocks" patch that replaces spinlocks with
priority inheriting mutexes --- but it also shows up on large SMP
benchmarks.
Thanks to John Stultz for pointing this out.
Reviewed by Mingming Cao and Jan Kara.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Delay discarding buffers in journal_unmap_buffer until
we know that "add to orphan" operation has definitely been
committed, otherwise the log space of committing transation
may be freed and reused before truncate get committed, updates
may get lost if crash happens.
Signed-off-by: dingdinghua <dingdinghua@nrchpc.ac.cn>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
lockdep annotation for a transaction start has been at the end of
jbd2_journal_start(). But a transaction is also started from
jbd2_journal_restart(). Move the lockdep annotation to start_this_handle()
which covers both cases.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
fix jiffie rounding in jbd commit timer setup code. Rounding down
could cause the timer to be fired before the corresponding transaction
has expired. That transaction can stay not committed forever if no
new transaction is created or expicit sync/umount happens.
Signed-off-by: Alex Zhuravlev (Tomas) <alex.zhuravlev@sun.com>
Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This patch reverts 3f31fddf, which is no longer needed because if a
race between freeing buffer and committing transaction functionality
occurs and dio gets error, currently dio falls back to buffered IO due
to the commit 6ccfa806.
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Cc: Mingming Cao <cmm@us.ibm.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
The following race can happen:
CPU1 CPU2
checkpointing code checks the buffer, adds
it to an array for writeback
do_get_write_access()
...
lock_buffer()
unlock_buffer()
flush_batch() submits the buffer for IO
__jbd2_journal_file_buffer()
So a buffer under writeout is returned from
do_get_write_access(). Since the filesystem code relies on the fact
that journaled buffers cannot be written out, it does not take the
buffer lock and so it can modify buffer while it is under
writeout. That can lead to a filesystem corruption if we crash at the
right moment.
We fix the problem by clearing the buffer dirty bit under buffer_lock
even if the buffer is on BJ_None list. Actually, we clear the dirty
bit regardless the list the buffer is in and warn about the fact if
the buffer is already journalled.
Thanks for spotting the problem goes to dingdinghua <dingdinghua85@gmail.com>.
Reported-by: dingdinghua <dingdinghua85@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
If a commit is triggered by fsync(), set a flag indicating the journal
blocks associated with the transaction should be flushed out using
WRITE_SYNC.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
If we race with commit code setting i_transaction to NULL, we could
possibly dereference it. Proper locking requires the journal pointer
(to access journal->j_list_lock), which we don't have. So we have to
change the prototype of the function so that filesystem passes us the
journal pointer. Also add a more detailed comment about why the
function jbd2_journal_begin_ordered_truncate() does what it does and
how it should be used.
Thanks to Dan Carpenter <error27@gmail.com> for pointing to the
suspitious code.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Joel Becker <joel.becker@oracle.com>
CC: linux-ext4@vger.kernel.org
CC: ocfs2-devel@oss.oracle.com
CC: mfasheh@suse.de
CC: Dan Carpenter <error27@gmail.com>
Filesystems often to do compute intensive operation on some
metadata. If this operation is repeated many times, it can be very
expensive. It would be much nicer if the operation could be performed
once before a buffer goes to disk.
This adds triggers to jbd2 buffer heads. Just before writing a metadata
buffer to the journal, jbd2 will optionally call a commit trigger associated
with the buffer. If the journal is aborted, an abort trigger will be
called on any dirty buffers as they are dropped from pending
transactions.
ocfs2 will use this feature.
Initially I tried to come up with a more generic trigger that could be
used for non-buffer-related events like transaction completion. It
doesn't tie nicely, because the information a buffer trigger needs
(specific to a journal_head) isn't the same as what a transaction
trigger needs (specific to a tranaction_t or perhaps journal_t). So I
implemented a buffer set, with the understanding that
journal/transaction wide triggers should be implemented separately.
There is only one trigger set allowed per buffer. I can't think of any
reason to attach more than one set. Contrast this with a journal or
transaction in which multiple places may want to watch the entire
transaction separately.
The trigger sets are considered static allocation from the jbd2
perspective. ocfs2 will just have one trigger set per block type,
setting the same set on every bh of the same type.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Add new mount options, min_batch_time and max_batch_time, which
controls how long the jbd2 layer should wait for additional filesystem
operations to get batched with a synchronous write transaction.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This patch removes the static sleep time in favor of a more self
optimizing approach where we measure the average amount of time it
takes to commit a transaction to disk and the ammount of time a
transaction has been running. If somebody does a sync write or an
fsync() traditionally we would sleep for 1 jiffies, which depending on
the value of HZ could be a significant amount of time compared to how
long it takes to commit a transaction to the underlying storage. With
this patch instead of sleeping for a jiffie, we check to see if the
amount of time this transaction has been running is less than the
average commit time, and if it is we sleep for the delta using
schedule_hrtimeout to give us a higher precision sleep time. This
greatly benefits high end storage where you could end up sleeping for
longer than it takes to commit the transaction and therefore sitting
idle instead of allowing the transaction to be committed by keeping
the sleep time to a minimum so you are sure to always be doing
something.
Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
The multiblock allocator needs to be able to release blocks (and issue
a blkdev discard request) when the transaction which freed those
blocks is committed. Previously this was done via a polling mechanism
when blocks are allocated or freed. A much better way of doing things
is to create a jbd2 callback function and attaching the list of blocks
to be freed directly to the transaction structure.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
the names were too generic:
drivers/uio/uio.c:87: error: expected identifier or '(' before 'do'
drivers/uio/uio.c:87: error: expected identifier or '(' before 'while'
drivers/uio/uio.c:113: error: 'map_release' undeclared here (not in a function)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Most the free-standing lock_acquire() usages look remarkably similar, sweep
them into a new helper.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds necessary framework into JBD2 to be able to track inodes
with each transaction and write-out their dirty data during transaction
commit time.
This new ordered mode brings all sorts of advantages such as possibility
to get rid of journal heads and buffer heads for data buffers in ordered
mode, better ordering of writes on transaction commit, simplification of
some JBD code, no more anonymous pages when truncate of data being
committed happens. Also with this new ordered mode, delayed allocation
on ordered mode is much simpler.
Signed-off-by: Jan Kara <jack@suse.cz>
journal_try_to_free_buffers() could race with jbd commit transaction
when the later is holding the buffer reference while waiting for the
data buffer to flush to disk. If the caller of
journal_try_to_free_buffers() request tries hard to release the buffers,
it will treat the failure as error and return back to the caller. We
have seen the directo IO failed due to this race. Some of the caller of
releasepage() also expecting the buffer to be dropped when passed with
GFP_KERNEL mask to the releasepage()->journal_try_to_free_buffers().
With this patch, if the caller is passing the GFP_KERNEL to indicating
this call could wait, in case of try_to_free_buffers() failed, let's
waiting for journal_commit_transaction() to finish commit the current
committing transaction , then try to free those buffers again with
journal locked.
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Reviewed-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Jan Kara