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Commit 550ac1d8 authored by Gerhard Heift's avatar Gerhard Heift Committed by Chris Mason
Browse files

btrfs: new function read_extent_buffer_to_user 



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

Signed-off-by: default avatarGerhard Heift <Gerhard@Heift.Name>
Signed-off-by: default avatarChris Mason <clm@fb.com>
Acked-by: default avatarDavid Sterba <dsterba@suse.cz>
parent 9b6e817d

fs/btrfs/extent_io.c

+37 −0
Original line number Diff line number Diff line
@@ -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,

fs/btrfs/extent_io.h

+3 −0
Original line number Diff line number Diff line
@@ -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,