From 3f8a028ede974bfa2eb3b55df44be600b4d09198 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Sun, 1 Mar 2020 12:34:10 -0500
Subject: [PATCH] libxfs: introduce libxfs_buf_read_uncached

Introduce an uncached read function so that userspace can handle them in
the same way as the kernel.  This also eliminates the need for some of
the libxfs_purgebuf calls (and two trips into the cache code).

Refactor the get/read uncached buffer functions to hide the details of
uncached buffer-ism in rdwr.c.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 libxfs/libxfs_api_defs.h |  2 ++
 libxfs/libxfs_io.h       | 22 +++----------
 libxfs/rdwr.c            | 67 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 17 deletions(-)

diff --git a/libxfs/libxfs_api_defs.h b/libxfs/libxfs_api_defs.h
index df267c98a..1149e301f 100644
--- a/libxfs/libxfs_api_defs.h
+++ b/libxfs/libxfs_api_defs.h
@@ -45,7 +45,9 @@
 #define xfs_btree_init_block		libxfs_btree_init_block
 #define xfs_buf_delwri_submit		libxfs_buf_delwri_submit
 #define xfs_buf_get			libxfs_buf_get
+#define xfs_buf_get_uncached		libxfs_buf_get_uncached
 #define xfs_buf_read			libxfs_buf_read
+#define xfs_buf_read_uncached		libxfs_buf_read_uncached
 #define xfs_buf_relse			libxfs_buf_relse
 #define xfs_bunmapi			libxfs_bunmapi
 #define xfs_bwrite			libxfs_bwrite
diff --git a/libxfs/libxfs_io.h b/libxfs/libxfs_io.h
index d96b5318e..21afc99c1 100644
--- a/libxfs/libxfs_io.h
+++ b/libxfs/libxfs_io.h
@@ -255,23 +255,11 @@ xfs_buf_associate_memory(struct xfs_buf *bp, void *mem, size_t len)
 	return 0;
 }
 
-/*
- * Allocate an uncached buffer that points nowhere.  The refcount will be 1,
- * and the cache node hash list will be empty to indicate that it's uncached.
- */
-static inline struct xfs_buf *
-xfs_buf_get_uncached(struct xfs_buftarg *targ, size_t bblen, int flags)
-{
-	struct xfs_buf	*bp;
-
-	bp = libxfs_getbufr(targ, XFS_BUF_DADDR_NULL, bblen);
-	if (!bp)
-		return NULL;
-
-	INIT_LIST_HEAD(&bp->b_node.cn_hash);
-	bp->b_node.cn_count = 1;
-	return bp;
-}
+struct xfs_buf *libxfs_buf_get_uncached(struct xfs_buftarg *targ, size_t bblen,
+		int flags);
+int libxfs_buf_read_uncached(struct xfs_buftarg *targ, xfs_daddr_t daddr,
+		size_t bblen, int flags, struct xfs_buf **bpp,
+		const struct xfs_buf_ops *ops);
 
 /* Push a single buffer on a delwri queue. */
 static inline void
diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index 2c67edded..3b4702664 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -1073,6 +1073,73 @@ libxfs_readbuf_map(struct xfs_buftarg *btp, struct xfs_buf_map *map, int nmaps,
 	return bp;
 }
 
+/* Allocate a raw uncached buffer. */
+static inline struct xfs_buf *
+libxfs_getbufr_uncached(
+	struct xfs_buftarg	*targ,
+	xfs_daddr_t		daddr,
+	size_t			bblen)
+{
+	struct xfs_buf		*bp;
+
+	bp = libxfs_getbufr(targ, daddr, bblen);
+	if (!bp)
+		return NULL;
+
+	INIT_LIST_HEAD(&bp->b_node.cn_hash);
+	bp->b_node.cn_count = 1;
+	return bp;
+}
+
+/*
+ * Allocate an uncached buffer that points nowhere.  The refcount will be 1,
+ * and the cache node hash list will be empty to indicate that it's uncached.
+ */
+struct xfs_buf *
+libxfs_buf_get_uncached(
+	struct xfs_buftarg	*targ,
+	size_t			bblen,
+	int			flags)
+{
+	return libxfs_getbufr_uncached(targ, XFS_BUF_DADDR_NULL, bblen);
+}
+
+/*
+ * Allocate and read an uncached buffer.  The refcount will be 1, and the cache
+ * node hash list will be empty to indicate that it's uncached.
+ */
+int
+libxfs_buf_read_uncached(
+	struct xfs_buftarg	*targ,
+	xfs_daddr_t		daddr,
+	size_t			bblen,
+	int			flags,
+	struct xfs_buf		**bpp,
+	const struct xfs_buf_ops *ops)
+{
+	struct xfs_buf		*bp;
+	int			error;
+
+	*bpp = NULL;
+	bp = libxfs_getbufr_uncached(targ, daddr, bblen);
+	if (!bp)
+		return -ENOMEM;
+
+	error = libxfs_readbufr(targ, daddr, bp, bblen, flags);
+	if (error)
+		goto err;
+
+	error = libxfs_readbuf_verify(bp, ops);
+	if (error)
+		goto err;
+
+	*bpp = bp;
+	return 0;
+err:
+	libxfs_buf_relse(bp);
+	return error;
+}
+
 static int
 __write_buf(int fd, void *buf, int len, off64_t offset, int flags)
 {
-- 
2.47.3