Commit 212260aa authored Jan 13, 2011 by Rik van Riel Committed by Linus Torvalds Jan 13, 2011

mm: clear PageError bit in msync & fsync



Temporary IO failures, eg.  due to loss of both multipath paths, can
permanently leave the PageError bit set on a page, resulting in msync or
fsync returning -EIO over and over again, even if IO is now getting to the
disk correctly.

We already clear the AS_ENOSPC and AS_IO bits in mapping->flags in the
filemap_fdatawait_range function.  Also clearing the PageError bit on the
page allows subsequent msync or fsync calls on this file to return without
an error, if the subsequent IO succeeds.

Unfortunately data written out in the msync or fsync call that returned
-EIO can still get lost, because the page dirty bit appears to not get
restored on IO error.  However, the alternative could be potentially all
of memory filling up with uncleanable dirty pages, hanging the system, so
there is no nice choice here...

Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Valerie Aurora <vaurora@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent dabb16f6

include/linux/page-flags.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -198,7 +198,7 @@ static inline int __TestClearPage##uname(struct page *page) { return 0; }
		struct page; /* forward declaration */

		TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
		PAGEFLAG(Error, error)
		PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
		PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
		PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
		PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)

mm/filemap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -298,7 +298,7 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
		continue;

		wait_on_page_writeback(page);
		if (PageError(page))
		if (TestClearPageError(page))
		ret = -EIO;
		}
		pagevec_release(&pvec);

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