From 550ac1d85ef99f3390a6ea87c70b7683647f6110 Mon Sep 17 00:00:00 2001 From: Gerhard Heift Date: Thu, 30 Jan 2014 16:24:01 +0100 Subject: [PATCH] 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 Signed-off-by: Chris Mason Acked-by: David Sterba --- 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 0b5fa91d9a88..930f23dfaa2b 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -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, diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index 8b63f2d46518..15ce5f2a2b62 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, -- 2.20.1