diff mbox series

[2/2] iomap: Mark read blocks uptodate in write_begin

Message ID 20200907203707.3964-3-willy@infradead.org (mailing list archive)
State New
Headers show
Series Fix silent write loss in iomap | expand

Commit Message

Matthew Wilcox (Oracle) Sept. 7, 2020, 8:37 p.m. UTC
When bringing (portions of) a page uptodate, we were marking blocks that
were zeroed as being uptodate, but not blocks that were read from storage.

Like the previous commit, this problem was found with generic/127 and
a kernel which failed readahead I/Os.  This bug causes writes to be
silently lost when working with flaky storage.

Fixes: 9dc55f1389f9 ("iomap: add support for sub-pagesize buffered I/O without buffer heads")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/iomap/buffered-io.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

Comments

Christoph Hellwig Sept. 8, 2020, 3:03 p.m. UTC | #1
On Mon, Sep 07, 2020 at 09:37:07PM +0100, Matthew Wilcox (Oracle) wrote:
> When bringing (portions of) a page uptodate, we were marking blocks that
> were zeroed as being uptodate, but not blocks that were read from storage.
> 
> Like the previous commit, this problem was found with generic/127 and
> a kernel which failed readahead I/Os.  This bug causes writes to be
> silently lost when working with flaky storage.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index c95454784df4..897ab9a26a74 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -574,7 +574,6 @@  __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
 	loff_t block_start = pos & ~(block_size - 1);
 	loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1);
 	unsigned from = offset_in_page(pos), to = from + len, poff, plen;
-	int status;
 
 	if (PageUptodate(page))
 		return 0;
@@ -595,14 +594,13 @@  __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
 			if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
 				return -EIO;
 			zero_user_segments(page, poff, from, to, poff + plen);
-			iomap_set_range_uptodate(page, poff, plen);
-			continue;
+		} else {
+			int status = iomap_read_page_sync(block_start, page,
+					poff, plen, srcmap);
+			if (status)
+				return status;
 		}
-
-		status = iomap_read_page_sync(block_start, page, poff, plen,
-				srcmap);
-		if (status)
-			return status;
+		iomap_set_range_uptodate(page, poff, plen);
 	} while ((block_start += plen) < block_end);
 
 	return 0;