[Devel] [PATCH RHEL7 COMMIT] ms/dax: set errors in mapping when writeback fails

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-862.vz7.48.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-862.el7
------>
commit 24684d28c46938f3fb166adbeaaeb41b5fc877f3
Author: Vasily Averin <vvs at virtuozzo.com>
Date:   Sat Jun 9 13:29:37 2018 +0300

    ms/dax: set errors in mapping when writeback fails
    
    mainline commit ("dax: set errors in mapping when writeback fails")
    
    Jan Kara's description for this patch is much better than mine, so I'm
    quoting it verbatim here:
    
    DAX currently doesn't set errors in the mapping when cache flushing
    fails in dax_writeback_mapping_range(). Since this function can get
    called only from fsync(2) or sync(2), this is actually as good as it can
    currently get since we correctly propagate the error up from
    dax_writeback_mapping_range() to filemap_fdatawrite()
    
    However, in the future better writeback error handling will enable us to
    properly report these errors on fsync(2) even if there are multiple file
    descriptors open against the file or if sync(2) gets called before
    fsync(2). So convert DAX to using standard error reporting through the
    mapping.
    
    Signed-off-by: Jeff Layton <jlayton at redhat.com>
    Reviewed-by: Jan Kara <jack at suse.cz>
    Reviewed-by: Christoph Hellwig <hch at lst.de>
    Reviewed-and-tested-by: Ross Zwisler <ross.zwisler at linux.intel.com>
    Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 fs/dax.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6a798a9f5c05..e963575e04a5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -881,8 +881,10 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 			ret = dax_writeback_one(bdev, dax_dev, mapping,
 					indices[i], pvec.pages[i]);
-			if (ret < 0)
+			if (ret < 0) {
+				mapping_set_error(mapping, ret);
 				goto out;
+			}
 		}
 		start_index = indices[pvec.nr - 1] + 1;
 	}