linux-ext4 - [PATCH v4 27/27] mm: clean up comments in me_pagecache

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Message-Id: <20170509154930.29524-28-jlayton@redhat.com>
Date:   Tue,  9 May 2017 11:49:30 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-cifs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, jfs-discussion@...ts.sourceforge.net,
        linux-xfs@...r.kernel.org, cluster-devel@...hat.com,
        linux-f2fs-devel@...ts.sourceforge.net,
        v9fs-developer@...ts.sourceforge.net, linux-nilfs@...r.kernel.org,
        linux-block@...r.kernel.org
Cc:     dhowells@...hat.com, akpm@...ux-foundation.org, hch@...radead.org,
        ross.zwisler@...ux.intel.com, mawilcox@...rosoft.com,
        jack@...e.com, viro@...iv.linux.org.uk, corbet@....net,
        neilb@...e.de, clm@...com, tytso@....edu, axboe@...nel.dk,
        josef@...icpanda.com, hubcap@...ibond.com, rpeterso@...hat.com,
        bo.li.liu@...cle.com
Subject: [PATCH v4 27/27] mm: clean up comments in me_pagecache_dirty

This no longer applies with the new writeback error tracking and
reporting infrastructure.

Signed-off-by: Jeff Layton <jlayton@...hat.com>
---
 mm/memory-failure.c | 35 +++++------------------------------
 1 file changed, 5 insertions(+), 30 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 4b56e53e5378..be5f998a0772 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -642,37 +642,12 @@ static int me_pagecache_dirty(struct page *p, unsigned long pfn)
 	if (mapping) {
 		/*
 		 * IO error will be reported by write(), fsync(), etc.
-		 * who check the mapping.
-		 * This way the application knows that something went
-		 * wrong with its dirty file data.
+		 * who check the mapping. This way the application knows that
+		 * something went wrong when writing back its dirty file data.
 		 *
-		 * There's one open issue:
-		 *
-		 * The EIO will be only reported on the next IO
-		 * operation and then cleared through the IO map.
-		 * Normally Linux has two mechanisms to pass IO error
-		 * first through the AS_EIO flag in the address space
-		 * and then through the PageError flag in the page.
-		 * Since we drop pages on memory failure handling the
-		 * only mechanism open to use is through AS_AIO.
-		 *
-		 * This has the disadvantage that it gets cleared on
-		 * the first operation that returns an error, while
-		 * the PageError bit is more sticky and only cleared
-		 * when the page is reread or dropped.  If an
-		 * application assumes it will always get error on
-		 * fsync, but does other operations on the fd before
-		 * and the page is dropped between then the error
-		 * will not be properly reported.
-		 *
-		 * This can already happen even without hwpoisoned
-		 * pages: first on metadata IO errors (which only
-		 * report through AS_EIO) or when the page is dropped
-		 * at the wrong time.
-		 *
-		 * So right now we assume that the application DTRT on
-		 * the first EIO, but we're not worse than other parts
-		 * of the kernel.
+		 * Note that errors are reported only once per file
+		 * description, but should be reported on all open file
+		 * descriptions for this inode.
 		 */
 		mapping_set_error(mapping, -EIO);
 	}
-- 
2.9.3