On Wed, Jun 18, 2014 at 06:55:41PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> The allocation stack switch at xfs_bmapi_allocate() has served it's
> purpose, but is no longer a sufficient solution to the stack usage
> problem we have in the XFS allocation path.
>
...
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 4 +--
> fs/xfs/libxfs/xfs_btree.c | 84 +++++++++++++++++++++++++++++++++++++++++++++--
> fs/xfs/xfs_bmap_util.c | 53 ------------------------------
> fs/xfs/xfs_bmap_util.h | 2 --
> 4 files changed, 84 insertions(+), 59 deletions(-)
>
...
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 56f050e..43a9744 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -249,59 +249,6 @@ xfs_bmap_rtalloc(
> }
>
> /*
> - * Stack switching interfaces for allocation
> - */
> -static void
> -xfs_bmapi_allocate_worker(
> - struct work_struct *work)
> -{
> - struct xfs_bmalloca *args = container_of(work,
> - struct xfs_bmalloca, work);
> - unsigned long pflags;
> - unsigned long new_pflags = PF_FSTRANS;
> -
> - /*
> - * we are in a transaction context here, but may also be doing work
> - * in kswapd context, and hence we may need to inherit that state
> - * temporarily to ensure that we don't block waiting for memory reclaim
> - * in any way.
> - */
> - if (args->kswapd)
> - new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> -
> - current_set_flags_nested(&pflags, new_pflags);
> -
> - args->result = __xfs_bmapi_allocate(args);
> - complete(args->done);
> -
> - current_restore_flags_nested(&pflags, new_pflags);
> -}
> -
> -/*
> - * Some allocation requests often come in with little stack to work on. Push
> - * them off to a worker thread so there is lots of stack to use. Otherwise just
> - * call directly to avoid the context switch overhead here.
> - */
> -int
> -xfs_bmapi_allocate(
> - struct xfs_bmalloca *args)
> -{
> - DECLARE_COMPLETION_ONSTACK(done);
> -
> - if (!args->stack_switch)
> - return __xfs_bmapi_allocate(args);
Looks like we can kill args->stack_switch up through the controlling
XFS_BMAPI_STACK_SWITCH flag. The rest of the code looks fine to me,
though I need to do some testing...
Brian
> -
> -
> - args->done = &done;
> - args->kswapd = current_is_kswapd();
> - INIT_WORK_ONSTACK(&args->work, xfs_bmapi_allocate_worker);
> - queue_work(xfs_alloc_wq, &args->work);
> - wait_for_completion(&done);
> - destroy_work_on_stack(&args->work);
> - return args->result;
> -}
> -
> -/*
> * Check if the endoff is outside the last extent. If so the caller will grow
> * the allocation to a stripe unit boundary. All offsets are considered outside
> * the end of file for an empty fork, so 1 is returned in *eof in that case.
> diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
> index 075f722..5f8abb9 100644
> --- a/fs/xfs/xfs_bmap_util.h
> +++ b/fs/xfs/xfs_bmap_util.h
> @@ -66,8 +66,6 @@ struct xfs_bmalloca {
> int xfs_bmap_finish(struct xfs_trans **tp, struct xfs_bmap_free *flist,
> int *committed);
> int xfs_bmap_rtalloc(struct xfs_bmalloca *ap);
> -int xfs_bmapi_allocate(struct xfs_bmalloca *args);
> -int __xfs_bmapi_allocate(struct xfs_bmalloca *args);
> int xfs_bmap_eof(struct xfs_inode *ip, xfs_fileoff_t endoff,
> int whichfork, int *eof);
> int xfs_bmap_count_blocks(struct xfs_trans *tp, struct xfs_inode *ip,
> --
> 2.0.0
>
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