[PATCH 20/29] xfs: distinguish error type of memory allocation failure for nowait case

[Hao Xu <hao.xu@linux.dev>]

From: Hao Xu <howeyxu@tencent.com>

Previously, if we fail to get the memory we need, -ENOMEM is returned.
It can be -EAGAIN now since we support nowait now. Return the latter
when it is the case. Involved functions are:  _xfs_buf_map_pages(),
xfs_buf_get_maps(), xfs_buf_alloc_kmem() and xfs_buf_alloc_pages().

Signed-off-by: Hao Xu <howeyxu@tencent.com>
---
 fs/xfs/xfs_buf.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 8b800ce28996..a6e6e64ff940 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -192,7 +192,7 @@ xfs_buf_get_maps(
 	bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
 				KM_NOFS);
 	if (!bp->b_maps)
-		return -ENOMEM;
+		return bp->b_flags & XBF_NOWAIT ? -EAGAIN : -ENOMEM;
 	return 0;
 }
 
@@ -339,7 +339,7 @@ xfs_buf_alloc_kmem(
 
 	bp->b_addr = kmem_alloc(size, kmflag_mask);
 	if (!bp->b_addr)
-		return -ENOMEM;
+		return flags & XBF_NOWAIT ? -EAGAIN : -ENOMEM;
 
 	if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 	    ((unsigned long)bp->b_addr & PAGE_MASK)) {
@@ -363,6 +363,7 @@ xfs_buf_alloc_pages(
 {
 	gfp_t		gfp_mask = __GFP_NOWARN;
 	long		filled = 0;
+	bool		nowait = flags & XBF_NOWAIT;
 
 	if (flags & XBF_READ_AHEAD)
 		gfp_mask |= __GFP_NORETRY;
@@ -377,7 +378,7 @@ xfs_buf_alloc_pages(
 		bp->b_pages = kzalloc(sizeof(struct page *) * bp->b_page_count,
 					gfp_mask);
 		if (!bp->b_pages)
-			return -ENOMEM;
+			return nowait ? -EAGAIN : -ENOMEM;
 	}
 	bp->b_flags |= _XBF_PAGES;
 
@@ -451,7 +452,7 @@ _xfs_buf_map_pages(
 		memalloc_nofs_restore(nofs_flag);
 
 		if (!bp->b_addr)
-			return -ENOMEM;
+			return flags & XBF_NOWAIT ? -EAGAIN : -ENOMEM;
 	}
 
 	return 0;
-- 
2.25.1