[PATCH] xfs: flush vmap aliases when mapping fails

[Dave Chinner]

From: Dave Chinner <dchinner at redhat.com>

On 32 bit systems, vmalloc space is limited and XFS can chew through
it quickly as the vmalloc space is lazily freed. This can result in
failure to map buffers, even when there is apparently large amounts
of vmalloc space available. Hence, if we fail to map a buffer, purge
the aliases that have not yet been freed to hopefuly free up enough
vmalloc space to allow a retry to succeed.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
---
 fs/xfs/linux-2.6/xfs_buf.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 3cc671c..a5a260f 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -455,9 +455,17 @@ _xfs_buf_map_pages(
 		bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
 		bp->b_flags |= XBF_MAPPED;
 	} else if (flags & XBF_MAPPED) {
-		bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
-					-1, PAGE_KERNEL);
-		if (unlikely(bp->b_addr == NULL))
+		int retried = 0;
+
+		do {
+			bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
+						-1, PAGE_KERNEL);
+			if (bp->b_addr)
+				break;
+			vm_unmap_aliases();
+		} while (retried++ <= 1);
+
+		if (!bp->b_addr)
 			return -ENOMEM;
 		bp->b_addr += bp->b_offset;
 		bp->b_flags |= XBF_MAPPED;
-- 
1.7.2.3