Advance the original, let the caller revert if it needs to.
Don't mess with iov_iter_single_seg_count() in the caller -
if we got a (non-zero) short copy, use the amount actually
copied for the next pass, limit it to "up to the end
of page" if nothing got copied at all.
Originally fault-in only read the first iovec; back then it used
to make sense to limit to the just one iovec for the pass after
short copy. These days it's no long true.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/ntfs/file.c | 33 +++++++++++----------------------
1 file changed, 11 insertions(+), 22 deletions(-)
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index e5aab265dff1..0666d4578137 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1684,20 +1684,19 @@ static size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
{
struct page **last_page = pages + nr_pages;
size_t total = 0;
- struct iov_iter data = *i;
unsigned len, copied;
do {
len = PAGE_SIZE - ofs;
if (len > bytes)
len = bytes;
- copied = iov_iter_copy_from_user_atomic(*pages, &data, ofs,
+ copied = iov_iter_copy_from_user_atomic(*pages, i, ofs,
len);
+ iov_iter_advance(i, copied);
total += copied;
bytes -= copied;
if (!bytes)
break;
- iov_iter_advance(&data, copied);
if (copied < len)
goto err;
ofs = 0;
@@ -1866,34 +1865,24 @@ static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
if (likely(copied == bytes)) {
status = ntfs_commit_pages_after_write(pages, do_pages,
pos, bytes);
- if (!status)
- status = bytes;
}
do {
unlock_page(pages[--do_pages]);
put_page(pages[do_pages]);
} while (do_pages);
- if (unlikely(status < 0))
+ if (unlikely(status < 0)) {
+ iov_iter_revert(i, copied);
break;
- copied = status;
+ }
cond_resched();
- if (unlikely(!copied)) {
- size_t sc;
-
- /*
- * We failed to copy anything. Fall back to single
- * segment length write.
- *
- * This is needed to avoid possible livelock in the
- * case that all segments in the iov cannot be copied
- * at once without a pagefault.
- */
- sc = iov_iter_single_seg_count(i);
- if (bytes > sc)
- bytes = sc;
+ if (unlikely(copied < bytes)) {
+ iov_iter_revert(i, copied);
+ if (copied)
+ bytes = copied;
+ else if (bytes > PAGE_SIZE - ofs)
+ bytes = PAGE_SIZE - ofs;
goto again;
}
- iov_iter_advance(i, copied);
pos += copied;
written += copied;
balance_dirty_pages_ratelimited(mapping);
--
2.11.0
