linux-kernel - [PATCH v7 1/6] dax: fallback from pmd to pte on error

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Message-Id: <1463000932-31680-2-git-send-email-vishal.l.verma@intel.com>
Date:	Wed, 11 May 2016 15:08:47 -0600
From:	Vishal Verma <vishal.l.verma@...el.com>
To:	linux-nvdimm@...ts.01.org
Cc:	Dan Williams <dan.j.williams@...el.com>,
	linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
	xfs@....sgi.com, linux-ext4@...r.kernel.org, linux-mm@...ck.org,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
	Jens Axboe <axboe@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Jeff Moyer <jmoyer@...hat.com>,
	Boaz Harrosh <boaz@...xistor.com>
Subject: [PATCH v7 1/6] dax: fallback from pmd to pte on error

From: Dan Williams <dan.j.williams@...el.com>

In preparation for consulting a badblocks list in pmem_direct_access(),
teach dax_pmd_fault() to fallback rather than fail immediately upon
encountering an error.  The thought being that reducing the span of the
dax request may avoid the error region.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 fs/dax.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9bc6624..d602410 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -855,8 +855,8 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		long length = dax_map_atomic(bdev, &dax);
 
 		if (length < 0) {
-			result = VM_FAULT_SIGBUS;
-			goto out;
+			dax_pmd_dbg(&bh, address, "dax-error fallback");
+			goto fallback;
 		}
 		if (length < PMD_SIZE) {
 			dax_pmd_dbg(&bh, address, "dax-length too small");
-- 
2.5.5