1,231 changes: 540 additions & 691 deletions lib/iov_iter.c

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36 changes: 15 additions & 21 deletions mm/filemap.c
Original file line number Diff line number Diff line change
Expand Up @@ -3642,10 +3642,6 @@ ssize_t generic_perform_write(struct file *file,
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*
* Not only is this an optimisation, but it is also required
* to check that the address is actually valid, when atomic
* usercopies are used, below.
*/
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
status = -EFAULT;
Expand All @@ -3665,33 +3661,31 @@ ssize_t generic_perform_write(struct file *file,
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);

copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
flush_dcache_page(page);

status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status < 0))
break;
copied = status;

if (unlikely(status != copied)) {
iov_iter_revert(i, copied - max(status, 0L));
if (unlikely(status < 0))
break;
}
cond_resched();

iov_iter_advance(i, copied);
if (unlikely(copied == 0)) {
if (unlikely(status == 0)) {
/*
* If we were unable to copy any data at all, we must
* fall back to a single segment length write.
*
* If we didn't fallback here, we could livelock
* because not all segments in the iov can be copied at
* once without a pagefault.
* A short copy made ->write_end() reject the
* thing entirely. Might be memory poisoning
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_single_seg_count(i));
if (copied)
bytes = copied;
goto again;
}
pos += copied;
written += copied;
pos += status;
written += status;

balance_dirty_pages_ratelimited(mapping);
} while (iov_iter_count(i));
Expand Down