From: Matthew Wilcox (Oracle) <[email protected]>
[ Upstream commit e6e7ca92623a43156100306861272e04d46385fc ]
If we find a page in write_begin which is !Uptodate, we need
to clear any error on the page before starting to read data
into it. This matches how filemap_fault(), do_read_cache_page()
and generic_file_buffered_read() handle PageError on !Uptodate pages.
When calling iomap_set_range_uptodate() in __iomap_write_begin(), blocks
were not being marked as uptodate.
This was found with generic/127 and a specially modified kernel which
would fail (some) readahead I/Os. The test read some bytes in a prior
page which caused readahead to extend into page 0x34. There was
a subsequent write to page 0x34, followed by a read to page 0x34.
Because the blocks were still marked as !Uptodate, the read caused all
blocks to be re-read, overwriting the write. With this change, and the
next one, the bytes which were written are marked as being Uptodate, so
even though the page is still marked as !Uptodate, the blocks containing
the written data are not re-read from storage.
Fixes: 9dc55f1389f9 ("iomap: add support for sub-pagesize buffered I/O without
buffer heads")
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
fs/iomap/buffered-io.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index a30ea7ecb790a..80867a1a94f26 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -559,6 +559,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos,
unsigned len,
if (PageUptodate(page))
return 0;
+ ClearPageError(page);
do {
iomap_adjust_read_range(inode, iop, &block_start,
--
2.25.1
