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authorAl Viro <viro@zeniv.linux.org.uk>2014-04-03 15:05:18 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-05-06 17:39:42 -0400
commitf0d1bec9d58d4c038d0ac958c9af82be6eb18045 (patch)
treedd8f6896941a030b723fedbaff6e64e3073ba6fc /mm
parent84c3d55cc474f9c234c023c92e2769f940d5548c (diff)
downloadlinux-f0d1bec9d58d4c038d0ac958c9af82be6eb18045.tar.gz
new helper: copy_page_from_iter()
parallel to copy_page_to_iter(). pipe_write() switched to it (and became ->write_iter()). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'mm')
-rw-r--r--mm/iov_iter.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index a5c691c1a283..081e3273085b 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -82,6 +82,84 @@ done:
}
EXPORT_SYMBOL(copy_page_to_iter);
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, left, wanted;
+ const struct iovec *iov;
+ char __user *buf;
+ void *kaddr, *to;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ iov = i->iov;
+ skip = i->iov_offset;
+ buf = iov->iov_base + skip;
+ copy = min(bytes, iov->iov_len - skip);
+
+ if (!fault_in_pages_readable(buf, copy)) {
+ kaddr = kmap_atomic(page);
+ to = kaddr + offset;
+
+ /* first chunk, usually the only one */
+ left = __copy_from_user_inatomic(to, buf, copy);
+ copy -= left;
+ skip += copy;
+ to += copy;
+ bytes -= copy;
+
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_from_user_inatomic(to, buf, copy);
+ copy -= left;
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ if (likely(!bytes)) {
+ kunmap_atomic(kaddr);
+ goto done;
+ }
+ offset = to - kaddr;
+ buf += copy;
+ kunmap_atomic(kaddr);
+ copy = min(bytes, iov->iov_len - skip);
+ }
+ /* Too bad - revert to non-atomic kmap */
+ kaddr = kmap(page);
+ to = kaddr + offset;
+ left = __copy_from_user(to, buf, copy);
+ copy -= left;
+ skip += copy;
+ to += copy;
+ bytes -= copy;
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_from_user(to, buf, copy);
+ copy -= left;
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ kunmap(page);
+done:
+ i->count -= wanted - bytes;
+ i->nr_segs -= iov - i->iov;
+ i->iov = iov;
+ i->iov_offset = skip;
+ return wanted - bytes;
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
const struct iovec *iov, size_t base, size_t bytes)
{