if we run into a short copy and ->write_end() refuses to advance at all,
use the amount we'd managed to copy for the next iteration to handle.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/iomap/buffered-io.c | 25 ++++++++++---------------
mm/filemap.c | 24 +++++++++---------------
2 files changed, 19 insertions(+), 30 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f2cd2034a87b..354b41d20e5d 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -771,10 +771,6 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
* 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;
@@ -791,25 +787,24 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
- copied = iomap_write_end(inode, pos, bytes, copied, page, iomap,
+ status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
srcmap);
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 iomap_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;
}
+ copied = status;
+ iov_iter_advance(i, copied);
pos += copied;
written += copied;
length -= copied;
diff --git a/mm/filemap.c b/mm/filemap.c
index 66f7e9fdfbc4..0be24942bf8e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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;
@@ -3672,24 +3668,22 @@ ssize_t generic_perform_write(struct file *file,
page, fsdata);
if (unlikely(status < 0))
break;
- copied = status;
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;
}
+ copied = status;
+ iov_iter_advance(i, copied);
pos += copied;
written += copied;
--
2.11.0
