linux-toradex.git/fs/reiserfs/stree.c, branch v3.2.17 Linux kernel for Apalis and Colibri modules dquot: cleanup space allocation / freeing routines 2010-03-04T23:20:28+00:00 Christoph Hellwig hch@infradead.org 2010-03-03T14:05:00+00:00 5dd4056db84387975140ff2568eaa0406f07985e Get rid of the alloc_space, free_space, reserve_space, claim_space and release_rsv dquot operations - they are always called from the filesystem and if a filesystem really needs their own (which none currently does) it can just call into it's own routine directly. Move shared logic into the common __dquot_alloc_space, dquot_claim_space_nodirty and __dquot_free_space low-level methods, and rationalize the wrappers around it to move as much as possible code into the common block for CONFIG_QUOTA vs not. Also rename all these helpers to be named dquot_* instead of vfs_dq_*. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> 
Get rid of the alloc_space, free_space, reserve_space, claim_space and
release_rsv dquot operations - they are always called from the filesystem
and if a filesystem really needs their own (which none currently does)
it can just call into it's own routine directly.

Move shared logic into the common __dquot_alloc_space,
dquot_claim_space_nodirty and __dquot_free_space low-level methods,
and rationalize the wrappers around it to move as much as possible
code into the common block for CONFIG_QUOTA vs not.  Also rename
all these helpers to be named dquot_* instead of vfs_dq_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
kill-the-bkl/reiserfs: move the concurrent tree accesses checks per superblock 2009-09-14T05:18:25+00:00 Frederic Weisbecker fweisbec@gmail.com 2009-05-16T17:10:38+00:00 08f14fc8963e585e65b71212ce8050607b9b6c36 When do_balance() balances the tree, a trick is performed to provide the ability for other tree writers/readers to check whether do_balance() is executing concurrently (requires CONFIG_REISERFS_CHECK). This is done to protect concurrent accesses to the tree. The trick is the following: When do_balance is called, a unique global variable called cur_tb takes a pointer to the current tree to be rebalanced. Once do_balance finishes its work, cur_tb takes the NULL value. Then, concurrent tree readers/writers just have to check the value of cur_tb to ensure do_balance isn't executing concurrently. If it is, then it proves that schedule() occured on do_balance(), which then relaxed the bkl that protected the tree. Now that the bkl has be turned into a mutex, this check is still fine even though do_balance() becomes preemptible: the write lock will not be automatically released on schedule(), so the tree is still protected. But this is only fine if we have a single reiserfs mountpoint. Indeed, because the bkl is a global lock, it didn't allowed concurrent executions between a tree reader/writer in a mount point and a do_balance() on another tree from another mountpoint. So assuming all these readers/writers weren't supposed to be reentrant, the current check now sometimes detect false positives with the current per-superblock mutex which allows this reentrancy. This patch keeps the concurrent tree accesses check but moves it per superblock, so that only trees from a same mount point are checked to be not accessed concurrently. [ Impact: fix spurious panic while running several reiserfs mount-points ] Cc: Jeff Mahoney <jeffm@suse.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> 
When do_balance() balances the tree, a trick is performed to
provide the ability for other tree writers/readers to check whether
do_balance() is executing concurrently (requires CONFIG_REISERFS_CHECK).

This is done to protect concurrent accesses to the tree. The trick
is the following:

When do_balance is called, a unique global variable called cur_tb
takes a pointer to the current tree to be rebalanced.
Once do_balance finishes its work, cur_tb takes the NULL value.

Then, concurrent tree readers/writers just have to check the value
of cur_tb to ensure do_balance isn't executing concurrently.
If it is, then it proves that schedule() occured on do_balance(),
which then relaxed the bkl that protected the tree.

Now that the bkl has be turned into a mutex, this check is still
fine even though do_balance() becomes preemptible: the write lock
will not be automatically released on schedule(), so the tree is
still protected.

But this is only fine if we have a single reiserfs mountpoint.
Indeed, because the bkl is a global lock, it didn't allowed
concurrent executions between a tree reader/writer in a mount point
and a do_balance() on another tree from another mountpoint.

So assuming all these readers/writers weren't supposed to be
reentrant, the current check now sometimes detect false positives with
the current per-superblock mutex which allows this reentrancy.

This patch keeps the concurrent tree accesses check but moves it
per superblock, so that only trees from a same mount point are
checked to be not accessed concurrently.

[ Impact: fix spurious panic while running several reiserfs mount-points ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
kill-the-bkl/reiserfs: unlock only when needed in search_by_key 2009-09-14T05:18:22+00:00 Frederic Weisbecker fweisbec@gmail.com 2009-05-14T00:56:39+00:00 2ac626955ed62ee8596f00581f959cc86e6198d1 search_by_key() is the site which most requires the lock. This is mostly because it is a very central function and also because it releases/reaqcuires the write lock at least once each time it is called. Such release/reacquire creates a lot of contention in this place and also opens more the window which let another thread changing the tree. When it happens, the current path searching over the tree must be retried from the beggining (the root) which is a wasteful and time consuming recovery. This patch factorizes two release/reacquire sequences: - reading leaf nodes blocks - reading current block The latter immediately follows the former. The whole sequence is safe as a single unlocked section because we check just after if the tree has changed during these operations. Cc: Jeff Mahoney <jeffm@suse.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> 
search_by_key() is the site which most requires the lock.
This is mostly because it is a very central function and also
because it releases/reaqcuires the write lock at least once each
time it is called.

Such release/reacquire creates a lot of contention in this place and
also opens more the window which let another thread changing the tree.
When it happens, the current path searching over the tree must be
retried from the beggining (the root) which is a wasteful and
time consuming recovery.

This patch factorizes two release/reacquire sequences:

- reading leaf nodes blocks
- reading current block

The latter immediately follows the former.

The whole sequence is safe as a single unlocked section because
we check just after if the tree has changed during these operations.

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
kill-the-bkl/reiserfs: reduce number of contentions in search_by_key() 2009-09-14T05:18:19+00:00 Frederic Weisbecker fweisbec@gmail.com 2009-05-08T12:21:33+00:00 09eb47a7c52ad535aafca889e0b936c445c375ce search_by_key() is a central function in reiserfs which searches the patch in the fs tree from the root to a node given its key. It is the function that is most requesting the write lock because it's a path very often used. Also we forget to release the lock while reading the next tree node, making us holding the lock in a wasteful way. Then we release the lock while reading the current node and its childs, all-in-one. It should be safe because we have a reference to these blocks and even if we read a block that will be concurrently changed, we have an fs_changed check later that will make us retry the path from the root. [ Impact: release the write lock while unused in a hot path ] Cc: Jeff Mahoney <jeffm@suse.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> 
search_by_key() is a central function in reiserfs which searches
the patch in the fs tree from the root to a node given its key.

It is the function that is most requesting the write lock
because it's a path very often used.

Also we forget to release the lock while reading the next tree node,
making us holding the lock in a wasteful way.

Then we release the lock while reading the current node and its childs,
all-in-one. It should be safe because we have a reference to these
blocks and even if we read a block that will be concurrently changed,
we have an fs_changed check later that will make us retry the path from
the root.

[ Impact: release the write lock while unused in a hot path ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
kill-the-BKL/reiserfs: release write lock while rescheduling on prepare_for_delete_or_cut() 2009-09-14T05:18:09+00:00 Frederic Weisbecker fweisbec@gmail.com 2009-04-30T21:36:33+00:00 5e69e3a4492ea5abfd2e8ddc575448becf28e4d9 prepare_for_delete_or_cut() can process several types of items, including indirect items, ie: items which contain no file data but pointers to unformatted nodes scattering the datas of a file. In this case it has to zero out these pointers to block numbers of unformatted nodes and release the bitmap from these block numbers. It can take some time, so a rescheduling() is performed between each block processed. We can safely release the write lock while rescheduling(), like the bkl did, because the code checks just after if the item has moved after sleeping. [ Impact: release the reiserfs write lock when it is not needed ] Cc: Jeff Mahoney <jeffm@suse.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> 
prepare_for_delete_or_cut() can process several types of items, including
indirect items, ie: items which contain no file data but pointers to
unformatted nodes scattering the datas of a file.

In this case it has to zero out these pointers to block numbers of
unformatted nodes and release the bitmap from these block numbers.

It can take some time, so a rescheduling() is performed between each
block processed. We can safely release the write lock while
rescheduling(), like the bkl did, because the code checks just after
if the item has moved after sleeping.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
reiserfs: kill-the-BKL 2009-09-14T05:17:59+00:00 Frederic Weisbecker fweisbec@gmail.com 2009-04-07T02:19:49+00:00 8ebc423238341b52912c7295b045a32477b33f09 This patch is an attempt to remove the Bkl based locking scheme from reiserfs and is intended. It is a bit inspired from an old attempt by Peter Zijlstra: http://lkml.indiana.edu/hypermail/linux/kernel/0704.2/2174.html The bkl is heavily used in this filesystem to prevent from concurrent write accesses on the filesystem. Reiserfs makes a deep use of the specific properties of the Bkl: - It can be acqquired recursively by a same task - It is released on the schedule() calls and reacquired when schedule() returns The two properties above are a roadmap for the reiserfs write locking so it's very hard to simply replace it with a common mutex. - We need a recursive-able locking unless we want to restructure several blocks of the code. - We need to identify the sites where the bkl was implictly relaxed (schedule, wait, sync, etc...) so that we can in turn release and reacquire our new lock explicitly. Such implicit releases of the lock are often required to let other resources producer/consumer do their job or we can suffer unexpected starvations or deadlocks. So the new lock that replaces the bkl here is a per superblock mutex with a specific property: it can be acquired recursively by a same task, like the bkl. For such purpose, we integrate a lock owner and a lock depth field on the superblock information structure. The first axis on this patch is to turn reiserfs_write_(un)lock() function into a wrapper to manage this mutex. Also some explicit calls to lock_kernel() have been converted to reiserfs_write_lock() helpers. The second axis is to find the important blocking sites (schedule...(), wait_on_buffer(), sync_dirty_buffer(), etc...) and then apply an explicit release of the write lock on these locations before blocking. Then we can safely wait for those who can give us resources or those who need some. Typically this is a fight between the current writer, the reiserfs workqueue (aka the async commiter) and the pdflush threads. The third axis is a consequence of the second. The write lock is usually on top of a lock dependency chain which can include the journal lock, the flush lock or the commit lock. So it's dangerous to release and trying to reacquire the write lock while we still hold other locks. This is fine with the bkl: T1 T2 lock_kernel() mutex_lock(A) unlock_kernel() // do something lock_kernel() mutex_lock(A) -> already locked by T1 schedule() (and then unlock_kernel()) lock_kernel() mutex_unlock(A) .... This is not fine with a mutex: T1 T2 mutex_lock(write) mutex_lock(A) mutex_unlock(write) // do something mutex_lock(write) mutex_lock(A) -> already locked by T1 schedule() mutex_lock(write) -> already locked by T2 deadlock The solution in this patch is to provide a helper which releases the write lock and sleep a bit if we can't lock a mutex that depend on it. It's another simulation of the bkl behaviour. The last axis is to locate the fs callbacks that are called with the bkl held, according to Documentation/filesystem/Locking. Those are: - reiserfs_remount - reiserfs_fill_super - reiserfs_put_super Reiserfs didn't need to explicitly lock because of the context of these callbacks. But now we must take care of that with the new locking. After this patch, reiserfs suffers from a slight performance regression (for now). On UP, a high volume write with dd reports an average of 27 MB/s instead of 30 MB/s without the patch applied. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Ingo Molnar <mingo@elte.hu> Cc: Jeff Mahoney <jeffm@suse.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Bron Gondwana <brong@fastmail.fm> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> LKML-Reference: <1239070789-13354-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> 
This patch is an attempt to remove the Bkl based locking scheme from
reiserfs and is intended.

It is a bit inspired from an old attempt by Peter Zijlstra:

   http://lkml.indiana.edu/hypermail/linux/kernel/0704.2/2174.html

The bkl is heavily used in this filesystem to prevent from
concurrent write accesses on the filesystem.

Reiserfs makes a deep use of the specific properties of the Bkl:

- It can be acqquired recursively by a same task
- It is released on the schedule() calls and reacquired when schedule() returns

The two properties above are a roadmap for the reiserfs write locking so it's
very hard to simply replace it with a common mutex.

- We need a recursive-able locking unless we want to restructure several blocks
  of the code.
- We need to identify the sites where the bkl was implictly relaxed
  (schedule, wait, sync, etc...) so that we can in turn release and
  reacquire our new lock explicitly.
  Such implicit releases of the lock are often required to let other
  resources producer/consumer do their job or we can suffer unexpected
  starvations or deadlocks.

So the new lock that replaces the bkl here is a per superblock mutex with a
specific property: it can be acquired recursively by a same task, like the
bkl.

For such purpose, we integrate a lock owner and a lock depth field on the
superblock information structure.

The first axis on this patch is to turn reiserfs_write_(un)lock() function
into a wrapper to manage this mutex. Also some explicit calls to
lock_kernel() have been converted to reiserfs_write_lock() helpers.

The second axis is to find the important blocking sites (schedule...(),
wait_on_buffer(), sync_dirty_buffer(), etc...) and then apply an explicit
release of the write lock on these locations before blocking. Then we can
safely wait for those who can give us resources or those who need some.
Typically this is a fight between the current writer, the reiserfs workqueue
(aka the async commiter) and the pdflush threads.

The third axis is a consequence of the second. The write lock is usually
on top of a lock dependency chain which can include the journal lock, the
flush lock or the commit lock. So it's dangerous to release and trying to
reacquire the write lock while we still hold other locks.

This is fine with the bkl:

      T1                       T2

lock_kernel()
    mutex_lock(A)
    unlock_kernel()
    // do something
                            lock_kernel()
                                mutex_lock(A) -> already locked by T1
                                schedule() (and then unlock_kernel())
    lock_kernel()
    mutex_unlock(A)
    ....

This is not fine with a mutex:

      T1                       T2

mutex_lock(write)
    mutex_lock(A)
    mutex_unlock(write)
    // do something
                           mutex_lock(write)
                              mutex_lock(A) -> already locked by T1
                              schedule()

    mutex_lock(write) -> already locked by T2
    deadlock

The solution in this patch is to provide a helper which releases the write
lock and sleep a bit if we can't lock a mutex that depend on it. It's another
simulation of the bkl behaviour.

The last axis is to locate the fs callbacks that are called with the bkl held,
according to Documentation/filesystem/Locking.

Those are:

- reiserfs_remount
- reiserfs_fill_super
- reiserfs_put_super

Reiserfs didn't need to explicitly lock because of the context of these callbacks.
But now we must take care of that with the new locking.

After this patch, reiserfs suffers from a slight performance regression (for now).
On UP, a high volume write with dd reports an average of 27 MB/s instead
of 30 MB/s without the patch applied.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Bron Gondwana <brong@fastmail.fm>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
LKML-Reference: <1239070789-13354-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Merge branch 'reiserfs-updates' from Jeff Mahoney 2009-03-30T19:33:01+00:00 Linus Torvalds torvalds@linux-foundation.org 2009-03-30T19:29:21+00:00 e1c502482853f84606928f5a2f2eb6da1993cda1 * reiserfs-updates: (35 commits) reiserfs: rename [cn]_* variables reiserfs: rename p_._ variables reiserfs: rename p_s_tb to tb reiserfs: rename p_s_inode to inode reiserfs: rename p_s_bh to bh reiserfs: rename p_s_sb to sb reiserfs: strip trailing whitespace reiserfs: cleanup path functions reiserfs: factor out buffer_info initialization reiserfs: add atomic addition of selinux attributes during inode creation reiserfs: use generic readdir for operations across all xattrs reiserfs: journaled xattrs reiserfs: use generic xattr handlers reiserfs: remove i_has_xattr_dir reiserfs: make per-inode xattr locking more fine grained reiserfs: eliminate per-super xattr lock reiserfs: simplify xattr internal file lookups/opens reiserfs: Clean up xattrs when REISERFS_FS_XATTR is unset reiserfs: remove IS_PRIVATE helpers reiserfs: remove link detection code ... Fixed up conflicts manually due to: - quota name cleanups vs variable naming changes: fs/reiserfs/inode.c fs/reiserfs/namei.c fs/reiserfs/stree.c fs/reiserfs/xattr.c - exported include header cleanups include/linux/reiserfs_fs.h 
* reiserfs-updates: (35 commits)
  reiserfs: rename [cn]_* variables
  reiserfs: rename p_._ variables
  reiserfs: rename p_s_tb to tb
  reiserfs: rename p_s_inode to inode
  reiserfs: rename p_s_bh to bh
  reiserfs: rename p_s_sb to sb
  reiserfs: strip trailing whitespace
  reiserfs: cleanup path functions
  reiserfs: factor out buffer_info initialization
  reiserfs: add atomic addition of selinux attributes during inode creation
  reiserfs: use generic readdir for operations across all xattrs
  reiserfs: journaled xattrs
  reiserfs: use generic xattr handlers
  reiserfs: remove i_has_xattr_dir
  reiserfs: make per-inode xattr locking more fine grained
  reiserfs: eliminate per-super xattr lock
  reiserfs: simplify xattr internal file lookups/opens
  reiserfs: Clean up xattrs when REISERFS_FS_XATTR is unset
  reiserfs: remove IS_PRIVATE helpers
  reiserfs: remove link detection code
  ...

Fixed up conflicts manually due to:
 - quota name cleanups vs variable naming changes:
	fs/reiserfs/inode.c
	fs/reiserfs/namei.c
	fs/reiserfs/stree.c
        fs/reiserfs/xattr.c
 - exported include header cleanups
	include/linux/reiserfs_fs.h
reiserfs: rename [cn]_* variables 2009-03-30T19:16:40+00:00 Jeff Mahoney jeffm@suse.com 2009-03-30T18:02:50+00:00 ee93961be1faddf9e9a638bc519145c20f0cfeba This patch renames n_, c_, etc variables to something more sane. This is the sixth in a series of patches to rip out some of the awful variable naming in reiserfs. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This patch renames n_, c_, etc variables to something more sane.  This
is the sixth in a series of patches to rip out some of the awful
variable naming in reiserfs.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
reiserfs: rename p_._ variables 2009-03-30T19:16:40+00:00 Jeff Mahoney jeffm@suse.com 2009-03-30T18:02:49+00:00 d68caa9530a8ba54f97002e02bf6a0ad2462b8c0 This patch is a simple s/p_._//g to the reiserfs code. This is the fifth in a series of patches to rip out some of the awful variable naming in reiserfs. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This patch is a simple s/p_._//g to the reiserfs code.  This is the
fifth in a series of patches to rip out some of the awful variable
naming in reiserfs.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
reiserfs: rename p_s_tb to tb 2009-03-30T19:16:40+00:00 Jeff Mahoney jeffm@suse.com 2009-03-30T18:02:48+00:00 a063ae17925cafabe55ebe1957ca0e8c480bd132 This patch is a simple s/p_s_tb/tb/g to the reiserfs code. This is the fourth in a series of patches to rip out some of the awful variable naming in reiserfs. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This patch is a simple s/p_s_tb/tb/g to the reiserfs code.  This is the
fourth in a series of patches to rip out some of the awful variable
naming in reiserfs.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>