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btrfs: new function read_extent_buffer_to_user 

This new function reads the content of an extent directly to user memory.

Signed-off-by: Gerhard Heift <Gerhard@Heift.Name>
Signed-off-by: Chris Mason <clm@fb.com>
Acked-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Gerhard Heift 2014-01-30 16:24:01 +01:00 committed by Chris Mason
parent 9b6e817d02
commit 550ac1d85e
2 changed files with 40 additions and 0 deletions
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37
fs/btrfs/extent_io.c
View File

@ -5067,6 +5067,43 @@ 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,

3
fs/btrfs/extent_io.h
View File

@ -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,