Btrfs: stop using highmem for extent_buffers

The extent_buffers have a very complex interface where
we use HIGHMEM for metadata and try to cache a kmap mapping
to access the memory.

The next commit adds reader/writer locks, and concurrent use
of this kmap cache would make it even more complex.

This commit drops the ability to use HIGHMEM with extent buffers,
and rips out all of the related code.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 31 insertions, 69 deletions

diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c
index c0f7eca..bc1f6ad 100644
--- a/fs/btrfs/struct-funcs.c
+++ b/fs/btrfs/struct-funcs.c
@@ -50,36 +50,22 @@ u##bits btrfs_##name(struct extent_buffer *eb,				\
 	unsigned long part_offset = (unsigned long)s;			\
 	unsigned long offset = part_offset + offsetof(type, member);	\
 	type *p;							\
-	/* ugly, but we want the fast path here */			\
-	if (eb->map_token && offset >= eb->map_start &&			\
-	    offset + sizeof(((type *)0)->member) <= eb->map_start +	\
-	    eb->map_len) {						\
-		p = (type *)(eb->kaddr + part_offset - eb->map_start);	\
-		return le##bits##_to_cpu(p->member);			\
-	}								\
-	{								\
-		int err;						\
-		char *map_token;					\
-		char *kaddr;						\
-		int unmap_on_exit = (eb->map_token == NULL);		\
-		unsigned long map_start;				\
-		unsigned long map_len;					\
-		u##bits res;						\
-		err = map_extent_buffer(eb, offset,			\
-				sizeof(((type *)0)->member),		\
-				&map_token, &kaddr,			\
-				&map_start, &map_len, KM_USER1);	\
-		if (err) {						\
-			__le##bits leres;				\
-			read_eb_member(eb, s, type, member, &leres);	\
-			return le##bits##_to_cpu(leres);		\
-		}							\
-		p = (type *)(kaddr + part_offset - map_start);		\
-		res = le##bits##_to_cpu(p->member);			\
-		if (unmap_on_exit)					\
-			unmap_extent_buffer(eb, map_token, KM_USER1);	\
-		return res;						\
-	}								\
+	int err;						\
+	char *kaddr;						\
+	unsigned long map_start;				\
+	unsigned long map_len;					\
+	u##bits res;						\
+	err = map_private_extent_buffer(eb, offset,		\
+			sizeof(((type *)0)->member),		\
+			&kaddr, &map_start, &map_len);		\
+	if (err) {						\
+		__le##bits leres;				\
+		read_eb_member(eb, s, type, member, &leres);	\
+		return le##bits##_to_cpu(leres);		\
+	}							\
+	p = (type *)(kaddr + part_offset - map_start);		\
+	res = le##bits##_to_cpu(p->member);			\
+	return res;						\
 }									\
 void btrfs_set_##name(struct extent_buffer *eb,				\
 				    type *s, u##bits val)		\
@@ -87,36 +73,21 @@ void btrfs_set_##name(struct extent_buffer *eb,				\
 	unsigned long part_offset = (unsigned long)s;			\
 	unsigned long offset = part_offset + offsetof(type, member);	\
 	type *p;							\
-	/* ugly, but we want the fast path here */			\
-	if (eb->map_token && offset >= eb->map_start &&			\
-	    offset + sizeof(((type *)0)->member) <= eb->map_start +	\
-	    eb->map_len) {						\
-		p = (type *)(eb->kaddr + part_offset - eb->map_start);	\
-		p->member = cpu_to_le##bits(val);			\
-		return;							\
-	}								\
-	{								\
-		int err;						\
-		char *map_token;					\
-		char *kaddr;						\
-		int unmap_on_exit = (eb->map_token == NULL);		\
-		unsigned long map_start;				\
-		unsigned long map_len;					\
-		err = map_extent_buffer(eb, offset,			\
-				sizeof(((type *)0)->member),		\
-				&map_token, &kaddr,			\
-				&map_start, &map_len, KM_USER1);	\
-		if (err) {						\
-			__le##bits val2;				\
-			val2 = cpu_to_le##bits(val);			\
-			write_eb_member(eb, s, type, member, &val2);	\
-			return;						\
-		}							\
-		p = (type *)(kaddr + part_offset - map_start);		\
-		p->member = cpu_to_le##bits(val);			\
-		if (unmap_on_exit)					\
-			unmap_extent_buffer(eb, map_token, KM_USER1);	\
-	}								\
+	int err;						\
+	char *kaddr;						\
+	unsigned long map_start;				\
+	unsigned long map_len;					\
+	err = map_private_extent_buffer(eb, offset,		\
+			sizeof(((type *)0)->member),		\
+			&kaddr, &map_start, &map_len);		\
+	if (err) {						\
+		__le##bits val2;				\
+		val2 = cpu_to_le##bits(val);			\
+		write_eb_member(eb, s, type, member, &val2);	\
+		return;						\
+	}							\
+	p = (type *)(kaddr + part_offset - map_start);		\
+	p->member = cpu_to_le##bits(val);			\
 }
 
 #include "ctree.h"
@@ -125,15 +96,6 @@ void btrfs_node_key(struct extent_buffer *eb,
 		    struct btrfs_disk_key *disk_key, int nr)
 {
 	unsigned long ptr = btrfs_node_key_ptr_offset(nr);
-	if (eb->map_token && ptr >= eb->map_start &&
-	    ptr + sizeof(*disk_key) <= eb->map_start + eb->map_len) {
-		memcpy(disk_key, eb->kaddr + ptr - eb->map_start,
-			sizeof(*disk_key));
-		return;
-	} else if (eb->map_token) {
-		unmap_extent_buffer(eb, eb->map_token, KM_USER1);
-		eb->map_token = NULL;
-	}
 	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 		       struct btrfs_key_ptr, key, disk_key);
 }