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>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 5f38c460367e41c1d9c7f9dab04fb2af993f52dc..4805fdec8d6ebb85301d087dbc862443694cc195 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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)

diff --git a/mm/filemap.c b/mm/filemap.c
index 1a3dd5914726d4cc06f8f30e9d2594c176c361be..b4ad8e36c81a857c2a4fb392da9feb7c483cf641 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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);