This new function reads the content of an extent directly to user memory.
Signed-off-by: Gerhard Heift <Gerhard@xxxxxxxxxx>
---
fs/btrfs/extent_io.c | 37 +++++++++++++++++++++++++++++++++++++
fs/btrfs/extent_io.h | 3 +++
2 files changed, 40 insertions(+)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index fbe501d..d1e9dd8 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4956,6 +4956,43 @@ void read_extent_buffer(struct extent_buffer *eb, void *dstv,
}
}
+int read_extent_buffer_to_user(struct extent_buffer *eb, void __user *dstv,
+ unsigned long start,
+ unsigned long len)
+{
+ size_t cur;
+ size_t offset;
+ struct page *page;
+ char *kaddr;
+ char __user *dst = (char __user *)dstv;
+ size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+ unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+ int ret = 0;
+
+ WARN_ON(start > eb->len);
+ WARN_ON(start + len > eb->start + eb->len);
+
+ offset = (start_offset + start) & (PAGE_CACHE_SIZE - 1);
+
+ while (len > 0) {
+ page = extent_buffer_page(eb, i);
+
+ cur = min(len, (PAGE_CACHE_SIZE - offset));
+ kaddr = page_address(page);
+ if (copy_to_user(dst, kaddr + offset, cur)) {
+ ret = -EFAULT;
+ break;
+ }
+
+ dst += cur;
+ len -= cur;
+ offset = 0;
+ i++;
+ }
+
+ return ret;
+}
+
int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
unsigned long min_len, char **map,
unsigned long *map_start,
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 58b27e5..d0b1541 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -304,6 +304,9 @@ int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
void read_extent_buffer(struct extent_buffer *eb, void *dst,
unsigned long start,
unsigned long len);
+int read_extent_buffer_to_user(struct extent_buffer *eb, void __user *dst,
+ unsigned long start,
+ unsigned long len);
void write_extent_buffer(struct extent_buffer *eb, const void *src,
unsigned long start, unsigned long len);
void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
--
1.8.5.3
--
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