From 326c03555b914ff153ba5b40df87fd6e28e7e367 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 5 Oct 2012 11:06:58 +1000 Subject: xfs: introduce XFS_BMAPI_STACK_SWITCH Certain allocation paths through xfs_bmapi_write() are in situations where we have limited stack available. These are almost always in the buffered IO writeback path when convertion delayed allocation extents to real extents. The current stack switch occurs for userdata allocations, which means we also do stack switches for preallocation, direct IO and unwritten extent conversion, even those these call chains have never been implicated in a stack overrun. Hence, let's target just the single stack overun offended for stack switches. To do that, introduce a XFS_BMAPI_STACK_SWITCH flag that the caller can pass xfs_bmapi_write() to indicate it should switch stacks if it needs to do allocation. Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_alloc.h | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/xfs/xfs_alloc.h') diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h index 93be4a667ca1..ef7d4885dc2d 100644 --- a/fs/xfs/xfs_alloc.h +++ b/fs/xfs/xfs_alloc.h @@ -123,6 +123,7 @@ typedef struct xfs_alloc_arg { struct completion *done; struct work_struct work; int result; + char stack_switch; } xfs_alloc_arg_t; /* -- cgit From 1f3c785c3adb7d2b109ec7c8f10081d1294b03d3 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 5 Oct 2012 11:06:59 +1000 Subject: xfs: move allocation stack switch up to xfs_bmapi_allocate Switching stacks are xfs_alloc_vextent can cause deadlocks when we run out of worker threads on the allocation workqueue. This can occur because xfs_bmap_btalloc can make multiple calls to xfs_alloc_vextent() and even if xfs_alloc_vextent() fails it can return with the AGF locked in the current allocation transaction. If we then need to make another allocation, and all the allocation worker contexts are exhausted because the are blocked waiting for the AGF lock, holder of the AGF cannot get it's xfs-alloc_vextent work completed to release the AGF. Hence allocation effectively deadlocks. To avoid this, move the stack switch one layer up to xfs_bmapi_allocate() so that all of the allocation attempts in a single switched stack transaction occur in a single worker context. This avoids the problem of an allocation being blocked waiting for a worker thread whilst holding the AGF. Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_alloc.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'fs/xfs/xfs_alloc.h') diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h index ef7d4885dc2d..feacb061bab7 100644 --- a/fs/xfs/xfs_alloc.h +++ b/fs/xfs/xfs_alloc.h @@ -120,10 +120,6 @@ typedef struct xfs_alloc_arg { char isfl; /* set if is freelist blocks - !acctg */ char userdata; /* set if this is user data */ xfs_fsblock_t firstblock; /* io first block allocated */ - struct completion *done; - struct work_struct work; - int result; - char stack_switch; } xfs_alloc_arg_t; /* -- cgit