[PATCH] sg: reset 'res_in_use' after unlinking reserved array

[PATCH] sg: reset 'res_in_use' after unlinking reserved array

[Hannes Reinecke]

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.

Fixes: 1bc0eb0 ("scsi: sg: protect accesses to 'reserved' page array")
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/sg.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 8147147..06503c1 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2056,6 +2056,8 @@ static long sg_compat_ioctl(struct file *filp, unsigned int cmd_in, unsigned lon
 	req_schp->page_order = 0;
 	req_schp->sglist_len = 0;
 	srp->res_used = 0;
+	/* Called without mutex lock to avoid deadlock */
+	sfp->res_in_use = 0;
 }
 
 static Sg_request *
-- 
1.8.5.6

Re: [PATCH] sg: reset 'res_in_use' after unlinking reserved array

[Johannes Thumshirn]

On Mon, Apr 24, 2017 at 10:26:36AM +0200, Hannes Reinecke wrote:
> 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.
> 
> Fixes: 1bc0eb0 ("scsi: sg: protect accesses to 'reserved' page array")
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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Re: [PATCH] sg: reset 'res_in_use' after unlinking reserved array

[Christoph Hellwig]

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] sg: reset 'res_in_use' after unlinking reserved array

[Martin K. Petersen]

Hannes,

> 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.

Applied to 4.12/scsi-queue.

-- 
Martin K. Petersen	Oracle Linux Engineering