linux-kernel - [PATCH 4.4 14/16] scsi: sg: reset res_in

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Date:   Thu, 31 Aug 2017 17:44:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Todd Poynor <toddpoynor@...gle.com>
Subject: [PATCH 4.4 14/16] scsi: sg: reset res_in_use after unlinking reserved array

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Reinecke <hare@...e.de>

commit e791ce27c3f6a1d3c746fd6a8f8e36c9540ec6f9 upstream.

Once the reserved page array is unused we can reset the 'res_in_use'
state; here we can do a lazy update without holding the mutex as we only
need to check against concurrent access, not concurrent release.

[mkp: checkpatch]

Fixes: 1bc0eb044615 ("scsi: sg: protect accesses to 'reserved' page array")
Signed-off-by: Hannes Reinecke <hare@...e.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@...e.de>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Todd Poynor <toddpoynor@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/scsi/sg.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2052,6 +2052,8 @@ sg_unlink_reserve(Sg_fd * sfp, Sg_reques
 	req_schp->sglist_len = 0;
 	sfp->save_scat_len = 0;
 	srp->res_used = 0;
+	/* Called without mutex lock to avoid deadlock */
+	sfp->res_in_use = 0;
 }

 static Sg_request *