[PATCH] nfs: set block size according to pnfs_blksize first

[Gao Xiang <hsiangkao@linux.alibaba.com>]

When testing fstests with ext4 over nfs 4.2, I found generic/486
failed. The root cause is that the length of its xattr value is
  min(st_blksize * 3 / 4, XATTR_SIZE_MAX)

which is 4096 * 3 / 4 = 3072 for underlayfs ext4 rather than
XATTR_SIZE_MAX = 65536 for nfs since the block size would be wsize
(=131072) if bsize is not specified.

Let's use pnfs_blksize first instead of using wsize directly if
bsize isn't specified. And the testcase itself can pass now.

Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
Considering bsize is not specified, we might use pnfs_blksize
directly first rather than wsize.

 fs/nfs/super.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index fe58525cfed4..5015edf0cd9a 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1068,9 +1068,13 @@ static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
 	snprintf(sb->s_id, sizeof(sb->s_id),
 		 "%u:%u", MAJOR(sb->s_dev), MINOR(sb->s_dev));
 
-	if (sb->s_blocksize == 0)
-		sb->s_blocksize = nfs_block_bits(server->wsize,
+	if (sb->s_blocksize == 0) {
+		unsigned int blksize = server->pnfs_blksize ?
+			server->pnfs_blksize : server->wsize;
+
+		sb->s_blocksize = nfs_block_bits(blksize,
 						 &sb->s_blocksize_bits);
+	}
 
 	nfs_super_set_maxbytes(sb, server->maxfilesize);
 	server->has_sec_mnt_opts = ctx->has_sec_mnt_opts;
-- 
1.8.3.1