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[v8,07/18] mm: don't TestClearPageError in __filemap_fdatawait_range

Message ID 20170629131954.28733-8-jlayton@kernel.org (mailing list archive)
State New, archived
Headers show

Commit Message

Jeff Layton June 29, 2017, 1:19 p.m. UTC
From: Jeff Layton <jlayton@redhat.com>

The -EIO returned here can end up overriding whatever error is marked in
the address space, and be returned at fsync time, even when there is a
more appropriate error stored in the mapping.

Read errors are also sometimes tracked on a per-page level using
PG_error. Suppose we have a read error on a page, and then that page is
subsequently dirtied by overwriting the whole page. Writeback doesn't
clear PG_error, so we can then end up successfully writing back that
page and still return -EIO on fsync.

Worse yet, PG_error is cleared during a sync() syscall, but the -EIO
return from that is silently discarded. Any subsystem that is relying on
PG_error to report errors during fsync can easily lose writeback errors
due to this. All you need is a stray sync() call to wait for writeback
to complete and you've lost the error.

Since the handling of the PG_error flag is somewhat inconsistent across
subsystems, let's just rely on marking the address space when there are
writeback errors. Change the TestClearPageError call to ClearPageError,
and make __filemap_fdatawait_range a void return function.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
 mm/filemap.c | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)
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diff --git a/mm/filemap.c b/mm/filemap.c
index 49bc9720fb00..eb99b5f23c61 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -386,17 +386,16 @@  int filemap_flush(struct address_space *mapping)
-static int __filemap_fdatawait_range(struct address_space *mapping,
+static void __filemap_fdatawait_range(struct address_space *mapping,
 				     loff_t start_byte, loff_t end_byte)
 	pgoff_t index = start_byte >> PAGE_SHIFT;
 	pgoff_t end = end_byte >> PAGE_SHIFT;
 	struct pagevec pvec;
 	int nr_pages;
-	int ret = 0;
 	if (end_byte < start_byte)
-		goto out;
+		return;
 	pagevec_init(&pvec, 0);
 	while ((index <= end) &&
@@ -413,14 +412,11 @@  static int __filemap_fdatawait_range(struct address_space *mapping,
-			if (TestClearPageError(page))
-				ret = -EIO;
+			ClearPageError(page);
-	return ret;
@@ -440,14 +436,8 @@  static int __filemap_fdatawait_range(struct address_space *mapping,
 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 			    loff_t end_byte)
-	int ret, ret2;
-	ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
-	ret2 = filemap_check_errors(mapping);
-	if (!ret)
-		ret = ret2;
-	return ret;
+	__filemap_fdatawait_range(mapping, start_byte, end_byte);
+	return filemap_check_errors(mapping);