linux-kernel - [PATCH v2 9/9] Documentation: document what to do on a writeback error

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Message-Id: <20170308162934.21989-10-jlayton@redhat.com>
Date:   Wed,  8 Mar 2017 11:29:34 -0500
From:   Jeff Layton <jlayton@...hat.com>
To:     viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Cc:     konishi.ryusuke@....ntt.co.jp, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-nilfs@...r.kernel.org, ross.zwisler@...ux.intel.com,
        jack@...e.cz, neilb@...e.com, openosd@...il.com, adilger@...ger.ca,
        James.Bottomley@...senPartnership.com
Subject: [PATCH v2 9/9] Documentation: document what to do on a writeback error

There's no real guidance on this for filesystem authors, so add a
paragraph to vfs.txt that explains how this should be handled.

Signed-off-by: Jeff Layton <jlayton@...hat.com>
---
 Documentation/filesystems/vfs.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 569211703721..527370fbab39 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -577,6 +577,13 @@ should clear PG_Dirty and set PG_Writeback.  It can be actually
 written at any point after PG_Dirty is clear.  Once it is known to be
 safe, PG_Writeback is cleared.
 
+If there is an error during writeback, then the address_space should be
+marked with an AS_EIO or AS_ENOSPC error, in order to ensure that the
+error will be reported to the application at fsync or close.  Most
+writepage callers will do this automatically if writepage returns an
+error, but writepages implementations generally need to ensure this
+themselves.
+
 Writeback makes use of a writeback_control structure...
 
 struct address_space_operations
-- 
2.9.3