Re: [PATCH v2 08/10] sg: completely protect sfds

[Douglas Gilbert <dgilbert@interlog.com>]

On 12-04-25 11:17 AM, Jörn Engel wrote:
> sfds is protected by sg_index_lock - except for sg_open(), where it
> isn't.  Change that and add some documentation.
>
> Signed-off-by: Joern Engel<joern@logfs.org>

Acked-by: Douglas Gilbert <dgilbert@interlog.com>

> ---
>   drivers/scsi/sg.c |   19 ++++++++++++++++---
>   1 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index e04b2a5..bb0514d 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -146,6 +146,7 @@ typedef struct sg_request {	/* SG_MAX_QUEUE requests outstanding per file */
>   } Sg_request;
>
>   typedef struct sg_fd {		/* holds the state of a file descriptor */
> +	/* sfd_siblings is protected by sg_index_lock */
>   	struct list_head sfd_siblings;
>   	struct sg_device *parentdp;	/* owning device */
>   	wait_queue_head_t read_wait;	/* queue read until command done */
> @@ -172,6 +173,7 @@ typedef struct sg_device { /* holds the state of each scsi generic device */
>   	wait_queue_head_t o_excl_wait;	/* queue open() when O_EXCL in use */
>   	int sg_tablesize;	/* adapter's max scatter-gather table size */
>   	u32 index;		/* device index number */
> +	/* sfds is protected by sg_index_lock */
>   	struct list_head sfds;
>   	volatile char detached;	/* 0->attached, 1->detached pending removal */
>   	/* exclude protected by sg_open_exclusive_lock */
> @@ -244,6 +246,17 @@ static int set_exclude(Sg_device *sdp, char val)
>   	return val;
>   }
>
> +static int sfds_list_empty(Sg_device *sdp)
> +{
> +	unsigned long flags;
> +	int ret;
> +
> +	read_lock_irqsave(&sg_index_lock, flags);
> +	ret = list_empty(&sdp->sfds);
> +	read_unlock_irqrestore(&sg_index_lock, flags);
> +	return ret;
> +}
> +
>   static int
>   sg_open(struct inode *inode, struct file *filp)
>   {
> @@ -287,12 +300,12 @@ sg_open(struct inode *inode, struct file *filp)
>   			retval = -EPERM; /* Can't lock it with read only access */
>   			goto error_out;
>   		}
> -		if (!list_empty(&sdp->sfds)&&  (flags&  O_NONBLOCK)) {
> +		if (!sfds_list_empty(sdp)&&  (flags&  O_NONBLOCK)) {
>   			retval = -EBUSY;
>   			goto error_out;
>   		}
>   		res = wait_event_interruptible(sdp->o_excl_wait,
> -					   ((!list_empty(&sdp->sfds) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
> +					   ((!sfds_list_empty(sdp) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
>   		if (res) {
>   			retval = res;	/* -ERESTARTSYS because signal hit process */
>   			goto error_out;
> @@ -312,7 +325,7 @@ sg_open(struct inode *inode, struct file *filp)
>   		retval = -ENODEV;
>   		goto error_out;
>   	}
> -	if (list_empty(&sdp->sfds)) {	/* no existing opens on this device */
> +	if (sfds_list_empty(sdp)) {	/* no existing opens on this device */
>   		sdp->sgdebug = 0;
>   		q = sdp->device->request_queue;
>   		sdp->sg_tablesize = queue_max_segments(q);

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