xfs: can't use kmem_zalloc() for attribute buffers

Because heap allocation of 64kB buffers will fail:

....
 XFS: fs_mark(8414) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8417) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8409) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8428) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8430) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8437) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8433) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8406) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8412) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8432) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
 XFS: fs_mark(8424) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
....

I'd use kvmalloc() instead, but....

- 48.19% xfs_attr_create_intent
  - 46.89% xfs_attri_init
     - kvmalloc_node
	- 46.04% __kmalloc_node
	   - kmalloc_large_node
	      - 45.99% __alloc_pages
		 - 39.39% __alloc_pages_slowpath.constprop.0
		    - 38.89% __alloc_pages_direct_compact
		       - 38.71% try_to_compact_pages
			  - compact_zone_order
			  - compact_zone
			     - 21.09% isolate_migratepages_block
				  10.31% PageHuge
				  5.82% set_pfnblock_flags_mask
				  0.86% get_pfnblock_flags_mask
			     - 4.48% __reset_isolation_suitable
				  4.44% __reset_isolation_pfn
			     - 3.56% __pageblock_pfn_to_page
				  1.33% pfn_to_online_page
			       2.83% get_pfnblock_flags_mask
			     - 0.87% migrate_pages
				  0.86% compaction_alloc
			       0.84% find_suitable_fallback
		 - 6.60% get_page_from_freelist
		      4.99% clear_page_erms
		    - 1.19% _raw_spin_lock_irqsave
		       - do_raw_spin_lock
			    __pv_queued_spin_lock_slowpath
	- 0.86% __vmalloc_node_range
	     0.65% __alloc_pages_bulk

.... this is just yet another reminder of how much kvmalloc() sucks.
So lift xlog_cil_kvmalloc(), rename it to xlog_kvmalloc() and use
that instead....

We also clean up the attribute name and value lengths as they no
longer need to be rounded out to sizes compatible with log vectors.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 4f7e844d28ad..67fd9789e69a 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -651,4 +651,38 @@ xlog_valid_lsn(
 	return valid;
 }
 
+/*
+ * Log vector and shadow buffers can be large, so we need to use kvmalloc() here
+ * to ensure success. Unfortunately, kvmalloc() only allows GFP_KERNEL contexts
+ * to fall back to vmalloc, so we can't actually do anything useful with gfp
+ * flags to control the kmalloc() behaviour within kvmalloc(). Hence kmalloc()
+ * will do direct reclaim and compaction in the slow path, both of which are
+ * horrendously expensive. We just want kmalloc to fail fast and fall back to
+ * vmalloc if it can't get somethign straight away from the free lists or
+ * buddy allocator. Hence we have to open code kvmalloc outselves here.
+ *
+ * This assumes that the caller uses memalloc_nofs_save task context here, so
+ * despite the use of GFP_KERNEL here, we are going to be doing GFP_NOFS
+ * allocations. This is actually the only way to make vmalloc() do GFP_NOFS
+ * allocations, so lets just all pretend this is a GFP_KERNEL context
+ * operation....
+ */
+static inline void *
+xlog_kvmalloc(
+	size_t		buf_size)
+{
+	gfp_t		flags = GFP_KERNEL;
+	void		*p;
+
+	flags &= ~__GFP_DIRECT_RECLAIM;
+	flags |= __GFP_NOWARN | __GFP_NORETRY;
+	do {
+		p = kmalloc(buf_size, flags);
+		if (!p)
+			p = vmalloc(buf_size);
+	} while (!p);
+
+	return p;
+}
+
 #endif	/* __XFS_LOG_PRIV_H__ */