Re: [PATCH 0/3] xfs: allocation worker causes freelist buffer lock hang

[Ben Myers <bpm@sgi.com>]

Hey Mark,

On Mon, Sep 24, 2012 at 01:09:04PM -0500, Mark Tinguely wrote:
> > From bpm@sgi.com Mon Sep 24 12:11:59 2012
> > Date: Mon, 24 Sep 2012 12:11:59 -0500
> > From: Ben Myers <bpm@sgi.com>
> > To: <tinguely@sgi.com>
> > Subject: Re: [PATCH 0/3] xfs: allocation worker causes freelist buffer lock
> > 	hang
> > Cc: <xfs@oss.sgi.com>
> >
> > Hi Mark,
> >
> > On Wed, Sep 19, 2012 at 11:31:33AM -0500, tinguely@sgi.com wrote:
> > ...
> > > I traced the callers of xfs_alloc_vextent(), noting transaction creation,
> > > commits and cancels; I noted loops in the callers and which were marked
> > > as metadata/userdata. I can send this document to reviewers.
> >
> > I'd like to see the doc of xfs_alloc_vextent callers and which of them loop.
> > Can you post your doc to the list?
> >
> > Regards,
> > 	Ben
> 
> 
> Here are the Linux 3.6.x callers of xfs_alloc_vextent() stopping at the
> transaction commit/cancel level.

Thanks.  Here I am going to make some notes to help me to understand the
deadlock as you have described.  I'm going to make some idiotic, redundant, and
obvious commentary for my own understanding and benefit, and then go and spam
the list with it.
 
> XFS_BMAPI_METADATA *not* being set implies user data.
>
> Userdata being set is the community designated indication that an allocate
> worker is needed to prevent the overflow of the kernel stack.

Even when XFS_BMAPI_METADATA is set, this doesn't necessarily translate into
userdata being clear in struct xfs_alloc_arg.  This is due to declaring that
structure on the stack and then forgetting to zero it.  You have fixed all
occurances of that in patch 3 of this series.  They are:

xfs_alloc_fix_freelist,
xfs_bmap_btalloc,	*
xfs_bmap_extents_to_btree,
xfs_bmap_local_to_extents,
xfs_ialloc_ag_alloc

In each of those five stacks we could have intended not to use a worker thread
for the allocation, but we used one anyway due to having forgotten to zero the
structure.

* In xfs_bmap_btalloc, args.userdata is set from ap->userdata before the first
call to xfs_alloc_vextent.  As long as ap->userdata is initialized properly
this one is ok.

> Calling xfs_alloc_vextent() several times with the same transaction can cause
> a dead lock if a new allocation worker can not be allocated. I noted where the
> loops occur. xfs_alloc_vextent() can call itself, those calls must be in the
> same allocation worker. 

This deadlock is characterized by a thread having taken the agf buffer lock in
this code path:

__xfs_alloc_vextent
  xfs_alloc_fix_freelist
    xfs_alloc_read_agf
      xfs_read_agf 

The agf buffer gets logged during allocation and stays locked until transaction
commit or cancel.

The deadlock comes when the transaction which holds the agf lock blocks waiting
for a worker, and all of the workers are blocked on the agf lock.

So... because the work being done in __xfs_alloc_vextent will always have need
of the agf buffer lock, we must never hold the agf lock and then go after a
worker thread for allocation.  The availability of a worker thread cannot be
guaranteed.

It's not just a problem with loops.  We risk deadlock on every call to
xfs_alloc_vextent in the same transaction while the agf lock is held.  e.g.
multiple tries in xfs_bmap_btalloc.

> As a bonus, consolidating the loops into one worker actually gives a slight
> performance advantage.
> 
> Sorry this is wider than 80 characters wide.
> 		---
> xfs_bmap_btalloc(xfs_bmalloca_t)

args.userdata = ap->userdata;	* not worried about patch 3 here

> ! xfs_bmap_alloc(xfs_bmalloca_t)
> ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! xfs_bmapi_write(xfs_trans_t ...)  loops over above

Here we risk deadlock in the loop on xfs_bmapi_allocate.  That appears to be
limited by the number of maps requested.

> ! ! ! ! xfs_attr_rmtval_set(xfs_da_args_t) loops over bmapi_write (xfs_attr_set_int) **XFS_BMAPI_METADATA**
> ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel

xfs_attr_rmtval_set calls xfs_bmapi_write in a loop.  XFS_BMAPI_METADATA flag
was set, so this cannot be using a worker.  No risk of this deadlock here.

> ! ! ! ! xfs_da_grow_inode_int(xfs_da_args_t) loops over bmapi_write **XFS_BMAPI_METADATA**
> ! ! ! ! ! xfs_dir2_grow_inode(struct xfs_da_args)
> ! ! ! ! ! ! xfs_dir2_sf_to_block(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_bmap_add_attrfork_local(xfs_trans_t ..)
> ! ! ! ! ! ! ! ! xfs_bmap_add_attrfork(...) trans alloc, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! xfs_dir2_sf_addname((xfs_da_args_t)
> ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_leaf_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_block_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! xfs_dir2_sf_addname((xfs_da_args_t)
> ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_leaf_to_node(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_dir2_leaf_addname(xfs_da_args_t) <also above>
> ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir2_block_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir2_sf_addname((xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_node_addname_int(xfs_da_args_t ...)
> ! ! ! ! ! ! ! xfs_dir2_node_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir2_leaf_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! xfs_da_grow_inode(xfs_da_args)
> ! ! ! ! ! ! xfs_attr_shortform_to_leaf(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_attr_set_int(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_attr_leaf_to_node(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! xfs_attr_leaf_split(xfs_da_state_t ...)
> ! ! ! ! ! ! ! xfs_da_split(xfs_da_state_t) loops over xfs_attr_leaf_split
> ! ! ! ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) trans_roll
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir2_node_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir2_leaf_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_da_root_split(xfs_da_state_t ...) <above>
> ! ! ! ! ! ! ! xfs_da_split(xfs_da_state_t) loops over xfs_attr_leaf_split
> ! ! ! ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) trans_roll
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! xfs_da_node_split(xfs_da_state_t ...)
> ! ! ! ! ! ! ! ! xfs_da_split(xfs_da_state_t) loops over xfs_attr_leaf_split
> ! ! ! ! ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) trans_roll
> ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! xfs_dir2_block_to_leaf(xfs_da_args_t ...)
> ! ! ! ! ! ! ! xfs_dir2_block_addname(xfs_da_args_t)
> ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! xfs_dir2_sf_addname((xfs_da_args_t)
> ! ! ! ! ! ! ! ! ! xfs_dir_createname(xfs_trans_t)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_dir_canenter(xfs_trans_t ...)
> ! ! ! ! ! ! ! ! ! ! xfs_rename(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_link(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_leafn_split(xfs_da_state_t...)
> ! ! ! ! ! ! ! xfs_da_split(xfs_da_state_t) loops over xfs_attr_leaf_split
> ! ! ! ! ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) trans_roll
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel

No risk of deadlock here due to XFS_BMAPI_METADATA flag.

> ! ! ! ! xfs_qm_dqalloc(xfs_trans_t ...) does a xfs_bmap_finish/cancel **XFS_BMAPI_METADATA**
> ! ! ! ! ! xfs_qm_dqtobp(xfs_trans_t ...)
> ! ! ! ! ! ! xfs_qm_dqread(...) does the trans_alloc/commit/cancel

No risk of deadlock here due to XFS_BMAPI_METADATA flag.

> ! ! ! ! xfs_iomap_write_direct(...) alloc trans, xfs_trans_commit/cancel

This allocates it's own transaction and will use a worker since it isn't
metadata.  Hmm.

> ! ! ! ! xfs_iomap_write_allocate(...) alloc trans, xfs_trans_commit/cancel safe loop

So this is a safe loop because the transaction alloc/commit is within the
loop... and nmap = 1.

Pfff.  This is in the stack you posted for this series.  So I'm a little confused.

I haven't got through the full list yet.  I'll send this today to keep things
moving and pick up again tomorrow.

Regards,
	Ben

> ! ! ! ! xfs_iomap_write_unwritten(..) alloc trans, xfs_trans_commit/cancel safe loop
> ! ! ! ! xfs_growfs_rt_alloc(..) alloc trans, xfs_trans_commit/cancel safe loop
> ! ! ! ! xfs_symlink(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! ! xfs_alloc_file_space(...) alloc trans, xfs_trans_commit/cancel safe loop
> 
> xfs_bmap_extents_to_btree(xfs_trans_t ...) <- set userdata to 0 (patch 3)
> ! xfs_bmap_add_attrfork_extents(xfs_trans_t ...)
> ! ! xfs_bmap_add_attrfork(...) allocates trans does a xfs_trans_commit/cancel
> ! xfs_bmap_add_extent_delay_real(fs_bmalloca)
> ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! <see above>
> ! xfs_bmap_add_extent_unwritten_real(xfs_trans_t ...)
> ! ! xfs_bmapi_convert_unwritten(xfs_bmalloca ...)
> ! ! ! xfs_bmapi_write(xfs_trans ...) calls xfs_bmapi_convert_unwritten in loop XFS_BMAPI_METADATA
> ! ! ! ! ... <see above>
> ! ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ! xfs_attr_rmtval_remove(xfs_da_args_t) loops calling xfs_bunmapi **XFS_BMAPI_METADATA**
> ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! xfs_attr_node_addname(xfs_da_args_t) trans_roll
> ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! xfs_attr_leaf_addname(xfs_da_args_t) may do a trans_roll
> ! ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! ! xfs_attr_set_int(..) does the trans_alloc/commit/cancel
> ! ! ! ! xfs_attr_node_removename(xfs_da_args_t)
> ! ! ! ! ! xfs_attr_remove_int(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! xfs_dir2_shrink_inode(xfs_da_args_t) **XFS_BMAPI_METADATA**
> ! ! ! ! xfs_dir2_leaf_trim_data(xfs_da_args_t)
> ! ! ! ! ! xfs_dir2_leaf_to_block(xfs_da_args_t ...)
> ! ! ! ! ! ! xfs_dir2_leaf_removename(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_dir_removename(xfs_trans ...)
> ! ! ! ! ! ! ! ! xfs_remove(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! ! xfs_dir2_leaf_trim_data(xfs_da_args_t)
> ! ! ! ! ! xfs_dir2_leaf_to_block(xfs_da_args_t ...)
> ! ! ! ! ! ! xfs_dir2_leaf_removename(xfs_da_args_t)
> ! ! ! ! ! ! ! xfs_dir_removename(xfs_trans ...)
> ! ! ! ! ! ! ! ! xfs_remove(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! ! ! ! xfs_dir2_node_to_leaf(xfs_da_state_t)
> ! ! ! ! ! ! ! xfs_dir2_node_removename(xfs_da_args_t)
> ! ! ! ! ! ! ! ! xfs_dir_removename(xfs_trans_t ...) creates the xfs_da_args_t
> ! ! ! ! ! ! ! ! ! xfs_remove(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! ! xfs_dir2_node_to_leaf(xfs_da_state_t)
> ! ! ! ! ! xfs_dir2_node_removename(xfs_da_args_t)
> ! ! ! ! ! ! xfs_dir_removename(xfs_trans_t ...) creates the xfs_da_args_t
> ! ! ! ! ! ! ! xfs_remove(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! xfs_bmap_punch_delalloc_range(...) loops calling xfs_bunmapi with NULL tp
> ! ! ! xfs_da_shrink_inode(xfs_da_args_t) loops calling xfs_bunmapi **XFS_BMAPI_METADATA**
> ! ! ! ! xfs_dir2_leaf_to_block(xfs_da_args_t ...)
> ! ! ! ! ! xfs_dir2_leaf_removename(xfs_da_args_t)
> ! ! ! ! ! ! xfs_dir_removename(xfs_trans ...)
> ! ! ! ! ! ! ! xfs_remove(...) allocates trans does a xfs_trans_commit/cancel
> ! ! ! xfs_itruncate_extents(xfs_trans ...) loops calling xfs_bunmapi with new tp
> ! ! ! xfs_inactive_symlink_rmt(..., xfs_trans_t) does a trans_commit and trans_dup
> ! ! ! xfs_free_file_space(...) loops calling xfs_bmapi with new tp
> ! xfs_bmap_add_extent_hole_real(xfs_bmalloca ...)
> ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! ... <see above>
> ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ... <see above>
> 
> xfs_bmap_local_to_extents(xfs_trans_t ...)     <- set userdata to 0 (patch 3)
> ! xfs_bmap_add_attrfork_local(xfs_trans_t ..)
> ! ! xfs_bmap_add_attrfork(...) trans alloc, bmap_finish trans_commit/cancel
> ! xfs_bmapi_write(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ... <see above>
> 
> xfs_ialloc_ag_alloc(xfs_trans_t ...) userdata == 0
> ! xfs_dialloc(xfs_trans ...) loops over the above
> ! ! xfs_ialloc(xfs_trans ...)
> ! ! ! xfs_dir_ialloc(xfs_trans ...)
> ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> 
> xfs_bmbt_alloc_block(xfs_btree_cur, ...) userdata == 0
> ! xfs_btree_split(xfs_btree_cur, ...)
> ! ! xfs_btree_make_block_unfull
> ! ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! xfs_free_ag_extent(xfs_trans ...)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! xfs_bmap_add_extent_delay_real(xfs_bmalloca)
> ! ! ! ! ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_add_extent_hole_real(xfs_bmalloca)
> ! ! ! ! ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_add_extent_unwritten_real(xfs_trans, ...)
> ! ! ! ! ! ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! ! xfs_bmapi_convert_unwritten(xfs_bmalloca, ...)
> ! ! ! ! ! ! ! xfs_bmapi_write(xfs_trans_t ...) loop over the above
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_del_extent(xfs_trans, ...) 
> ! ! ! ! ! ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_ialloc_ag_alloc(xfs_trans, ...) loops over the above
> ! ! ! ! ! ! xfs_dialloc(xfs_trans ...) loops over the above
> ! ! ! ! ! ! ! xfs_ialloc(xfs_trans ...)
> ! ! ! ! ! ! ! ! xfs_dir_ialloc(xfs_trans ...)
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! xfs_btree_new_iroot(xfs_btree_cur, ...)
> ! ! xfs_btree_make_block_unfull(xfs_btree_cur, ...)
> ! ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! xfs_bmap_add_attrfork_btree(xfs_trans_t ...)
> ! ! ! xfs_bmap_add_attrfork(...) allocates trans does a xfs_trans_commit/cancel
> ! xfs_btree_new_root(xfs_btree_cur, ...)
> ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> 
> xfs_inobt_alloc_block(xfs_btree_cur, ...) userdata == 0
> ! xfs_btree_split(xfs_btree_cur, ...)
> ! ! xfs_btree_make_block_unfull
> ! ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! xfs_free_ag_extent(xfs_trans ...)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! xfs_bmap_add_extent_delay_real(xfs_bmalloca)
> ! ! ! ! ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_add_extent_hole_real(xfs_bmalloca)
> ! ! ! ! ! ! xfs_bmapi_allocate(xfs_bmalloca_t, ...)
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_add_extent_unwritten_real(xfs_trans, ...)
> ! ! ! ! ! ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! ! xfs_bmapi_convert_unwritten(xfs_bmalloca, ...)
> ! ! ! ! ! ! ! xfs_bmapi_write(xfs_trans_t ...) loop over the above
> ! ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_bmap_del_extent(xfs_trans, ...) 
> ! ! ! ! ! ! xfs_bunmapi(xfs_trans_t ...) XFS_BMAPI_METADATA
> ! ! ! ! ! ! ! ... <see above>
> ! ! ! ! ! xfs_ialloc_ag_alloc(xfs_trans, ...) loops over the above
> ! ! ! ! ! ! xfs_dialloc(xfs_trans ...) loops over the above
> ! ! ! ! ! ! ! xfs_ialloc(xfs_trans ...)
> ! ! ! ! ! ! ! ! xfs_dir_ialloc(xfs_trans ...)
> ! ! ! ! ! ! ! ! ! xfs_create(...) trans allocated, bmap_finish trans_commit/cancel
> ! ! ! ! ! ! ! ! ! xfs_symlink(...) trans allocated, bmap_finish trans_commit/cancel
> ! xfs_btree_new_iroot(xfs_btree_cur, ...)
> ! ! xfs_btree_make_block_unfull(xfs_btree_cur, ...)
> ! ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! xfs_bmap_add_attrfork_btree(xfs_trans_t ...)
> ! ! ! xfs_bmap_add_attrfork(...) allocates trans does a xfs_trans_commit/cancel
> ! xfs_btree_new_root(xfs_btree_cur, ...)
> ! ! xfs_btree_insrec(xfs_btree_cur, ...)
> ! ! ! xfs_btree_insert(xfs_btree_cur, ...)
> ! ! ! xfs_alloc_fixup_trees(xfs_btree_cur, ...)
> ! ! ! ! xfs_alloc_ag_vextent_exact(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! xfs_alloc_ag_vextent_near(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> ! ! ! ! xfs_alloc_ag_vextent_size(xfs_alloc_arg)
> ! ! ! ! ! xfs_alloc_ag_vextent(xfs_alloc_arg)
> ! ! ! ! ! ! __xfs_alloc_vextent(xfs_alloc_arg)
> 
> --Mark.
> 
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