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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/fs/btrfs/struct-funcs.c
..
..
@@ -7,112 +7,152 @@
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 #include "ctree.h"
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-static inline u8 get_unaligned_le8(const void *p)
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+static bool check_setget_bounds(const struct extent_buffer *eb,
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+				const void *ptr, unsigned off, int size)
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 {
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-       return *(u8 *)p;
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-}
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+	const unsigned long member_offset = (unsigned long)ptr + off;
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-static inline void put_unaligned_le8(u8 val, void *p)
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-{
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-       *(u8 *)p = val;
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+	if (member_offset > eb->len) {
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+		btrfs_warn(eb->fs_info,
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+	"bad eb member start: ptr 0x%lx start %llu member offset %lu size %d",
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+			(unsigned long)ptr, eb->start, member_offset, size);
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+		return false;
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+	}
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+	if (member_offset + size > eb->len) {
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+		btrfs_warn(eb->fs_info,
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+	"bad eb member end: ptr 0x%lx start %llu member offset %lu size %d",
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+			(unsigned long)ptr, eb->start, member_offset, size);
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+		return false;
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+	}
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+
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+	return true;
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 }
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 /*
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- * this is some deeply nasty code.
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+ * Macro templates that define helpers to read/write extent buffer data of a
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+ * given size, that are also used via ctree.h for access to item members by
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+ * specialized helpers.
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  *
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- * The end result is that anyone who #includes ctree.h gets a
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- * declaration for the btrfs_set_foo functions and btrfs_foo functions,
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- * which are wrappers of btrfs_set_token_#bits functions and
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- * btrfs_get_token_#bits functions, which are defined in this file.
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+ * Generic helpers:
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+ * - btrfs_set_8 (for 8/16/32/64)
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+ * - btrfs_get_8 (for 8/16/32/64)
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  *
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- * These setget functions do all the extent_buffer related mapping
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- * required to efficiently read and write specific fields in the extent
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- * buffers.  Every pointer to metadata items in btrfs is really just
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- * an unsigned long offset into the extent buffer which has been
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- * cast to a specific type.  This gives us all the gcc type checking.
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+ * Generic helpers with a token (cached address of the most recently accessed
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+ * page):
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+ * - btrfs_set_token_8 (for 8/16/32/64)
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+ * - btrfs_get_token_8 (for 8/16/32/64)
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  *
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- * The extent buffer api is used to do the page spanning work required to
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- * have a metadata blocksize different from the page size.
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+ * The set/get functions handle data spanning two pages transparently, in case
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+ * metadata block size is larger than page.  Every pointer to metadata items is
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+ * an offset into the extent buffer page array, cast to a specific type.  This
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+ * gives us all the type checking.
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+ *
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+ * The extent buffer pages stored in the array pages do not form a contiguous
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+ * phyusical range, but the API functions assume the linear offset to the range
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+ * from 0 to metadata node size.
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  */
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 #define DEFINE_BTRFS_SETGET_BITS(bits)					\
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-u##bits btrfs_get_token_##bits(const struct extent_buffer *eb,		\
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-			       const void *ptr, unsigned long off,	\
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-			       struct btrfs_map_token *token)		\
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+u##bits btrfs_get_token_##bits(struct btrfs_map_token *token,		\
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+			       const void *ptr, unsigned long off)	\
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 {									\
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-	unsigned long part_offset = (unsigned long)ptr;			\
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-	unsigned long offset = part_offset + off;			\
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-	void *p;							\
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-	int err;							\
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-	char *kaddr;							\
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-	unsigned long map_start;					\
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-	unsigned long map_len;						\
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-	int size = sizeof(u##bits);					\
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-	u##bits res;							\
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+	const unsigned long member_offset = (unsigned long)ptr + off;	\
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+	const unsigned long idx = member_offset >> PAGE_SHIFT;		\
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+	const unsigned long oip = offset_in_page(member_offset);	\
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+	const int size = sizeof(u##bits);				\
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+	u8 lebytes[sizeof(u##bits)];					\
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+	const int part = PAGE_SIZE - oip;				\
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 									\
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-	if (token && token->kaddr && token->offset <= offset &&		\
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-	    token->eb == eb &&						\
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-	   (token->offset + PAGE_SIZE >= offset + size)) {	\
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-		kaddr = token->kaddr;					\
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-		p = kaddr + part_offset - token->offset;		\
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-		res = get_unaligned_le##bits(p + off);			\
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-		return res;						\
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+	ASSERT(token);							\
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+	ASSERT(token->kaddr);						\
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+	ASSERT(check_setget_bounds(token->eb, ptr, off, size));		\
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+	if (token->offset <= member_offset &&				\
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+	    member_offset + size <= token->offset + PAGE_SIZE) {	\
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+		return get_unaligned_le##bits(token->kaddr + oip);	\
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 	}								\
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-	err = map_private_extent_buffer(eb, offset, size,		\
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-					&kaddr, &map_start, &map_len);	\
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-	if (err) {							\
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-		__le##bits leres;					\
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+	token->kaddr = page_address(token->eb->pages[idx]);		\
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+	token->offset = idx << PAGE_SHIFT;				\
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+	if (oip + size <= PAGE_SIZE)					\
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+		return get_unaligned_le##bits(token->kaddr + oip);	\
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 									\
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-		read_extent_buffer(eb, &leres, offset, size);		\
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-		return le##bits##_to_cpu(leres);			\
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-	}								\
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-	p = kaddr + part_offset - map_start;				\
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-	res = get_unaligned_le##bits(p + off);				\
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-	if (token) {							\
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-		token->kaddr = kaddr;					\
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-		token->offset = map_start;				\
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-		token->eb = eb;						\
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-	}								\
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-	return res;							\
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+	memcpy(lebytes, token->kaddr + oip, part);			\
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+	token->kaddr = page_address(token->eb->pages[idx + 1]);		\
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+	token->offset = (idx + 1) << PAGE_SHIFT;			\
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+	memcpy(lebytes + part, token->kaddr, size - part);		\
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+	return get_unaligned_le##bits(lebytes);				\
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 }									\
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-void btrfs_set_token_##bits(struct extent_buffer *eb,			\
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-			    const void *ptr, unsigned long off,		\
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-			    u##bits val,				\
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-			    struct btrfs_map_token *token)		\
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+u##bits btrfs_get_##bits(const struct extent_buffer *eb,		\
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+			 const void *ptr, unsigned long off)		\
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 {									\
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-	unsigned long part_offset = (unsigned long)ptr;			\
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-	unsigned long offset = part_offset + off;			\
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-	void *p;							\
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-	int err;							\
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-	char *kaddr;							\
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-	unsigned long map_start;					\
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-	unsigned long map_len;						\
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-	int size = sizeof(u##bits);					\
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+	const unsigned long member_offset = (unsigned long)ptr + off;	\
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+	const unsigned long oip = offset_in_page(member_offset);	\
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+	const unsigned long idx = member_offset >> PAGE_SHIFT;		\
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+	char *kaddr = page_address(eb->pages[idx]);			\
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+	const int size = sizeof(u##bits);				\
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+	const int part = PAGE_SIZE - oip;				\
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+	u8 lebytes[sizeof(u##bits)];					\
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 									\
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-	if (token && token->kaddr && token->offset <= offset &&		\
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-	    token->eb == eb &&						\
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-	   (token->offset + PAGE_SIZE >= offset + size)) {	\
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-		kaddr = token->kaddr;					\
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-		p = kaddr + part_offset - token->offset;		\
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-		put_unaligned_le##bits(val, p + off);			\
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+	ASSERT(check_setget_bounds(eb, ptr, off, size));		\
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+	if (oip + size <= PAGE_SIZE)					\
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+		return get_unaligned_le##bits(kaddr + oip);		\
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+									\
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+	memcpy(lebytes, kaddr + oip, part);				\
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+	kaddr = page_address(eb->pages[idx + 1]);			\
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+	memcpy(lebytes + part, kaddr, size - part);			\
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+	return get_unaligned_le##bits(lebytes);				\
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+}									\
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+void btrfs_set_token_##bits(struct btrfs_map_token *token,		\
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+			    const void *ptr, unsigned long off,		\
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+			    u##bits val)				\
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+{									\
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+	const unsigned long member_offset = (unsigned long)ptr + off;	\
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+	const unsigned long idx = member_offset >> PAGE_SHIFT;		\
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+	const unsigned long oip = offset_in_page(member_offset);	\
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+	const int size = sizeof(u##bits);				\
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+	u8 lebytes[sizeof(u##bits)];					\
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+	const int part = PAGE_SIZE - oip;				\
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+									\
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+	ASSERT(token);							\
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+	ASSERT(token->kaddr);						\
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+	ASSERT(check_setget_bounds(token->eb, ptr, off, size));		\
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+	if (token->offset <= member_offset &&				\
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+	    member_offset + size <= token->offset + PAGE_SIZE) {	\
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+		put_unaligned_le##bits(val, token->kaddr + oip);	\
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 		return;							\
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 	}								\
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-	err = map_private_extent_buffer(eb, offset, size,		\
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-			&kaddr, &map_start, &map_len);			\
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-	if (err) {							\
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-		__le##bits val2;					\
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-									\
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-		val2 = cpu_to_le##bits(val);				\
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-		write_extent_buffer(eb, &val2, offset, size);		\
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+	token->kaddr = page_address(token->eb->pages[idx]);		\
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+	token->offset = idx << PAGE_SHIFT;				\
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+	if (oip + size <= PAGE_SIZE) {					\
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+		put_unaligned_le##bits(val, token->kaddr + oip);	\
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 		return;							\
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 	}								\
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-	p = kaddr + part_offset - map_start;				\
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-	put_unaligned_le##bits(val, p + off);				\
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-	if (token) {							\
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-		token->kaddr = kaddr;					\
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-		token->offset = map_start;				\
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-		token->eb = eb;						\
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+	put_unaligned_le##bits(val, lebytes);				\
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+	memcpy(token->kaddr + oip, lebytes, part);			\
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+	token->kaddr = page_address(token->eb->pages[idx + 1]);		\
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+	token->offset = (idx + 1) << PAGE_SHIFT;			\
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+	memcpy(token->kaddr, lebytes + part, size - part);		\
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+}									\
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+void btrfs_set_##bits(const struct extent_buffer *eb, void *ptr,	\
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+		      unsigned long off, u##bits val)			\
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+{									\
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+	const unsigned long member_offset = (unsigned long)ptr + off;	\
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+	const unsigned long oip = offset_in_page(member_offset);	\
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+	const unsigned long idx = member_offset >> PAGE_SHIFT;		\
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+	char *kaddr = page_address(eb->pages[idx]);			\
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+	const int size = sizeof(u##bits);				\
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+	const int part = PAGE_SIZE - oip;				\
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+	u8 lebytes[sizeof(u##bits)];					\
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+									\
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+	ASSERT(check_setget_bounds(eb, ptr, off, size));		\
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+	if (oip + size <= PAGE_SIZE) {					\
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+		put_unaligned_le##bits(val, kaddr + oip);		\
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+		return;							\
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 	}								\
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+									\
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+	put_unaligned_le##bits(val, lebytes);				\
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+	memcpy(kaddr + oip, lebytes, part);				\
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+	kaddr = page_address(eb->pages[idx + 1]);			\
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+	memcpy(kaddr, lebytes + part, size - part);			\
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 }
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 DEFINE_BTRFS_SETGET_BITS(8)