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-rw-r--r--mm/filemap.c36
1 files changed, 15 insertions, 21 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index ac82a93d4f38..d1458ecf2f51 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3642,10 +3642,6 @@ again:
* 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;
@@ -3665,33 +3661,31 @@ again:
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));