linux-kernel - [PATCH v2 4/8] buffer: Fix __bread and __bread

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Message-Id: <20240109143357.2375046-5-willy@infradead.org>
Date: Tue,  9 Jan 2024 14:33:53 +0000
From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
To: Jonathan Corbet <corbet@....net>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	linux-doc@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Pankaj Raghav <p.raghav@...sung.com>
Subject: [PATCH v2 4/8] buffer: Fix __bread and __bread_gfp kernel-doc

The extra indentation confused the kernel-doc parser, so remove it.
Fix some other wording while I'm here, and advise the user they need to
call brelse() on this buffer.

__bread_gfp() isn't used directly by filesystems, but the other wrappers
for it don't have documentation, so document it accordingly.

Co-developed-by: Pankaj Raghav <p.raghav@...sung.com>
Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/buffer.c                 | 35 ++++++++++++++++++++++-------------
 include/linux/buffer_head.h | 22 +++++++++++++---------
 2 files changed, 35 insertions(+), 22 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 25861241657f..160bbc1f929c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1453,20 +1453,29 @@ void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
 EXPORT_SYMBOL(__breadahead);
 
 /**
- *  __bread_gfp() - reads a specified block and returns the bh
- *  @bdev: the block_device to read from
- *  @block: number of block
- *  @size: size (in bytes) to read
- *  @gfp: page allocation flag
- *
- *  Reads a specified block, and returns buffer head that contains it.
- *  The page cache can be allocated from non-movable area
- *  not to prevent page migration if you set gfp to zero.
- *  It returns NULL if the block was unreadable.
+ * __bread_gfp() - Read a block.
+ * @bdev: The block device to read from.
+ * @block: Block number in units of block size.
+ * @size: The block size of this device in bytes.
+ * @gfp: Not page allocation flags; see below.
+ *
+ * You are not expected to call this function.  You should use one of
+ * sb_bread(), sb_bread_unmovable() or __bread().
+ *
+ * Read a specified block, and return the buffer head that refers to it.
+ * If @gfp is 0, the memory will be allocated using the block device's
+ * default GFP flags.  If @gfp is __GFP_MOVABLE, the memory may be
+ * allocated from a movable area.  Do not pass in a complete set of
+ * GFP flags.
+ *
+ * The returned buffer head has its refcount increased.  The caller should
+ * call brelse() when it has finished with the buffer.
+ *
+ * Context: May sleep waiting for I/O.
+ * Return: NULL if the block was unreadable.
  */
-struct buffer_head *
-__bread_gfp(struct block_device *bdev, sector_t block,
-		   unsigned size, gfp_t gfp)
+struct buffer_head *__bread_gfp(struct block_device *bdev, sector_t block,
+		unsigned size, gfp_t gfp)
 {
 	struct buffer_head *bh;
 
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index d78454a4dd1f..56a1e9c1e71e 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -437,17 +437,21 @@ static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[],
 }
 
 /**
- *  __bread() - reads a specified block and returns the bh
- *  @bdev: the block_device to read from
- *  @block: number of block
- *  @size: size (in bytes) to read
+ * __bread() - Read a block.
+ * @bdev: The block device to read from.
+ * @block: Block number in units of block size.
+ * @size: The block size of this device in bytes.
  *
- *  Reads a specified block, and returns buffer head that contains it.
- *  The page cache is allocated from movable area so that it can be migrated.
- *  It returns NULL if the block was unreadable.
+ * Read a specified block, and return the buffer head that refers
+ * to it.  The memory is allocated from the movable area so that it can
+ * be migrated.  The returned buffer head has its refcount increased.
+ * The caller should call brelse() when it has finished with the buffer.
+ *
+ * Context: May sleep waiting for I/O.
+ * Return: NULL if the block was unreadable.
  */
-static inline struct buffer_head *
-__bread(struct block_device *bdev, sector_t block, unsigned size)
+static inline struct buffer_head *__bread(struct block_device *bdev,
+		sector_t block, unsigned size)
 {
 	return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 }
-- 
2.43.0