From: Matthew Wilcox (Oracle) willy@infradead.org
[ Upstream commit 14284fedf59f1647264f4603d64418cf1fcd3eb0 ]
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 Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin sashal@kernel.org --- fs/iomap/buffered-io.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index c95454784df48..897ab9a26a74c 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;