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Commit 5e8fcc1a authored by Jeff Layton's avatar Jeff Layton
Browse files

mm: don't TestClearPageError in __filemap_fdatawait_range 



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: default avatarJeff Layton <jlayton@redhat.com>
parent cbeaf951

mm/filemap.c

+5 −15
Original line number Diff line number Diff line
@@ -386,17 +386,16 @@ int filemap_flush(struct address_space *mapping) 
}

EXPORT_SYMBOL(filemap_flush);



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, 
				continue;



			wait_on_page_writeback(page);

			if (TestClearPageError(page))

				ret = -EIO;

			ClearPageError(page);

		}

		pagevec_release(&pvec);

		cond_resched();

	}

out:

	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);

}

EXPORT_SYMBOL(filemap_fdatawait_range);