jim owens
2010-Jan-04 21:14 UTC
[RFC 09/12 PATCH] Btrfs: add direct I/O helper to process inline compressed extents.
Use access_extent_buffer_page() to point at btree location of
inline compressed data so it can be inflated without a memcopy.
Signed-off-by: jim owens <jowens@hp.com>
---
fs/btrfs/extent_io.c | 16 ++++++++++++++++
fs/btrfs/extent_io.h | 3 +++
2 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 96577e8..42b4cde 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3053,6 +3053,22 @@ static inline struct page *extent_buffer_page(struct
extent_buffer *eb,
return p;
}
+void access_extent_buffer_page(struct bio_vec *vec, struct extent_buffer *eb,
+ unsigned long start, unsigned long len)
+{
+ size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+ unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+ size_t offset = (start_offset + start) &
+ ((unsigned long)PAGE_CACHE_SIZE - 1);
+
+ WARN_ON(start > eb->len);
+ WARN_ON(start + len > eb->start + eb->len);
+
+ vec->bv_page = extent_buffer_page(eb, i);
+ vec->bv_offset = offset;
+ vec->bv_len = min(len, (PAGE_CACHE_SIZE - offset));
+}
+
static inline unsigned long num_extent_pages(u64 start, u64 len)
{
return ((start + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 36de250..c8c129b 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -2,6 +2,7 @@
#define __EXTENTIO__
#include <linux/rbtree.h>
+#include <linux/bio.h>
/* bits for the extent state */
#define EXTENT_DIRTY 1
@@ -300,4 +301,6 @@ int extent_clear_unlock_delalloc(struct inode *inode,
struct extent_io_tree *tree,
u64 start, u64 end, struct page *locked_page,
unsigned long op);
+extern void access_extent_buffer_page(struct bio_vec *vec, struct extent_buffer
*eb,
+ unsigned long start, unsigned long len);
#endif
--
1.5.6.3
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