linux-kernel - [PATCH 3.16 27/61] scsi: sg: reset 'res_in

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Message-ID: <lsq.1591725832.809977277@decadent.org.uk>
Date:   Tue, 09 Jun 2020 19:04:18 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Hannes Reinecke" <hare@...e.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Hannes Reinecke" <hare@...e.de>,
        "Todd Poynor" <toddpoynor@...gle.com>,
        "Christoph Hellwig" <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Johannes Thumshirn" <jthumshirn@...e.de>
Subject: [PATCH 3.16 27/61] scsi: sg: reset 'res_in_use' after unlinking
 reserved array

3.16.85-rc1 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>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/sg.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2062,6 +2062,8 @@ 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 *