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From: Matthew Wilcox <willy@infradead.org>
To: Josef Bacik <josef@toxicpanda.com>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: filemap_fault can lose errors
Date: Tue, 10 Sep 2019 19:51:58 -0700	[thread overview]
Message-ID: <20190911025158.GG29434@bombadil.infradead.org> (raw)


If we encounter an error on a page, we can lose the error if we've
dropped the mmap_sem while we wait for the I/O.  That can result in
taking the fault multiple times, and retrying the read multiple times.
Spotted by inspection.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations")

diff --git a/mm/filemap.c b/mm/filemap.c
index d0cf700bf201..37bd4aedfccf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2615,6 +2615,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 		if (!PageUptodate(page))
 			error = -EIO;
 	}
+	if (error < 0)
+		ret |= VM_FAULT_SIGBUS;
 	if (fpin)
 		goto out_retry;
 	put_page(page);
@@ -2622,9 +2624,9 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 	if (!error || error == AOP_TRUNCATED_PAGE)
 		goto retry_find;
 
-	/* Things didn't work out. Return zero to tell the mm layer so. */
+	/* Things didn't work out. */
 	shrink_readahead_size_eio(file, ra);
-	return VM_FAULT_SIGBUS;
+	return ret;
 
 out_retry:
 	/*


             reply	other threads:[~2019-09-11  2:52 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11  2:51 Matthew Wilcox [this message]
2019-09-11 15:23 ` filemap_fault can lose errors Kirill A. Shutemov

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