From c999a223c2f0d31c64ef7379814cea1378b2b800 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 22 Mar 2012 05:15:07 +0000 Subject: xfs: introduce an allocation workqueue We currently have significant issues with the amount of stack that allocation in XFS uses, especially in the writeback path. We can easily consume 4k of stack between mapping the page, manipulating the bmap btree and allocating blocks from the free list. Not to mention btree block readahead and other functionality that issues IO in the allocation path. As a result, we can no longer fit allocation in the writeback path in the stack space provided on x86_64. To alleviate this problem, introduce an allocation workqueue and move all allocations to a seperate context. This can be easily added as an interposing layer into xfs_alloc_vextent(), which takes a single argument structure and does not return until the allocation is complete or has failed. To do this, add a work structure and a completion to the allocation args structure. This allows xfs_alloc_vextent to queue the args onto the workqueue and wait for it to be completed by the worker. This can be done completely transparently to the caller. The worker function needs to ensure that it sets and clears the PF_TRANS flag appropriately as it is being run in an active transaction context. Work can also be queued in a memory reclaim context, so a rescuer is needed for the workqueue. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Ben Myers --- fs/xfs/xfs_alloc.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) (limited to 'fs/xfs/xfs_alloc.c') diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c index ce84ffd0264c..31e90335b83d 100644 --- a/fs/xfs/xfs_alloc.c +++ b/fs/xfs/xfs_alloc.c @@ -35,6 +35,7 @@ #include "xfs_error.h" #include "xfs_trace.h" +struct workqueue_struct *xfs_alloc_wq; #define XFS_ABSDIFF(a,b) (((a) <= (b)) ? ((b) - (a)) : ((a) - (b))) @@ -2207,7 +2208,7 @@ xfs_alloc_read_agf( * group or loop over the allocation groups to find the result. */ int /* error */ -xfs_alloc_vextent( +__xfs_alloc_vextent( xfs_alloc_arg_t *args) /* allocation argument structure */ { xfs_agblock_t agsize; /* allocation group size */ @@ -2417,6 +2418,37 @@ error0: return error; } +static void +xfs_alloc_vextent_worker( + struct work_struct *work) +{ + struct xfs_alloc_arg *args = container_of(work, + struct xfs_alloc_arg, work); + unsigned long pflags; + + /* we are in a transaction context here */ + current_set_flags_nested(&pflags, PF_FSTRANS); + + args->result = __xfs_alloc_vextent(args); + complete(args->done); + + current_restore_flags_nested(&pflags, PF_FSTRANS); +} + + +int /* error */ +xfs_alloc_vextent( + xfs_alloc_arg_t *args) /* allocation argument structure */ +{ + DECLARE_COMPLETION_ONSTACK(done); + + args->done = &done; + INIT_WORK(&args->work, xfs_alloc_vextent_worker); + queue_work(xfs_alloc_wq, &args->work); + wait_for_completion(&done); + return args->result; +} + /* * Free an extent. * Just break up the extent address and hand off to xfs_free_ag_extent -- cgit v1.2.3