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authorLinus Torvalds <torvalds@linux-foundation.org>2015-02-21 19:16:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-21 19:16:42 -0800
commitc8c6c9ba39e3fe65cf3497d692bf6fe808ff222b (patch)
tree4358c44f57f9ce1bfb5886aea8bea3b137ecb551 /drivers/scsi/sg.c
parent93aaa830fc173560505c3411806509299d8871ce (diff)
parent7772855a996ec6e16944b120ab5ce21050279821 (diff)
Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
Pull misc SCSI patches from James Bottomley: "This is a short patch set representing a couple of left overs from the merge window (debug removal and MAINTAINER changes). Plus one merge window regression (the local workqueue for hpsa) and a set of bug fixes for several issues (two for scsi-mq and the rest an assortment of long standing stuff, all cc'd to stable)" * tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: sg: fix EWOULDBLOCK errors with scsi-mq sg: fix unkillable I/O wait deadlock with scsi-mq sg: fix read() error reporting wd719x: add missing .module to wd719x_template hpsa: correct compiler warnings introduced by hpsa-add-local-workqueue patch fixed invalid assignment of 64bit mask to host dma_boundary for scatter gather segment boundary limit. fcoe: Transition maintainership to Vasu am53c974: remove left-over debugging code
Diffstat (limited to 'drivers/scsi/sg.c')
-rw-r--r--drivers/scsi/sg.c40
1 files changed, 33 insertions, 7 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0cbc1fb45f10..2270bd51f9c2 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -546,7 +546,7 @@ static ssize_t
sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
{
sg_io_hdr_t *hp = &srp->header;
- int err = 0;
+ int err = 0, err2;
int len;
if (count < SZ_SG_IO_HDR) {
@@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
goto err_out;
}
err_out:
- err = sg_finish_rem_req(srp);
- return (0 == err) ? count : err;
+ err2 = sg_finish_rem_req(srp);
+ return err ? : err2 ? : count;
}
static ssize_t
@@ -1335,6 +1335,17 @@ sg_rq_end_io(struct request *rq, int uptodate)
}
/* Rely on write phase to clean out srp status values, so no "else" */
+ /*
+ * Free the request as soon as it is complete so that its resources
+ * can be reused without waiting for userspace to read() the
+ * result. But keep the associated bio (if any) around until
+ * blk_rq_unmap_user() can be called from user context.
+ */
+ srp->rq = NULL;
+ if (rq->cmd != rq->__cmd)
+ kfree(rq->cmd);
+ __blk_put_request(rq->q, rq);
+
write_lock_irqsave(&sfp->rq_list_lock, iflags);
if (unlikely(srp->orphan)) {
if (sfp->keep_orphan)
@@ -1669,7 +1680,22 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
return -ENOMEM;
}
- rq = blk_get_request(q, rw, GFP_ATOMIC);
+ /*
+ * NOTE
+ *
+ * With scsi-mq enabled, there are a fixed number of preallocated
+ * requests equal in number to shost->can_queue. If all of the
+ * preallocated requests are already in use, then using GFP_ATOMIC with
+ * blk_get_request() will return -EWOULDBLOCK, whereas using GFP_KERNEL
+ * will cause blk_get_request() to sleep until an active command
+ * completes, freeing up a request. Neither option is ideal, but
+ * GFP_KERNEL is the better choice to prevent userspace from getting an
+ * unexpected EWOULDBLOCK.
+ *
+ * With scsi-mq disabled, blk_get_request() with GFP_KERNEL usually
+ * does not sleep except under memory pressure.
+ */
+ rq = blk_get_request(q, rw, GFP_KERNEL);
if (IS_ERR(rq)) {
kfree(long_cmdp);
return PTR_ERR(rq);
@@ -1759,10 +1785,10 @@ sg_finish_rem_req(Sg_request *srp)
SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sfp->parentdp,
"sg_finish_rem_req: res_used=%d\n",
(int) srp->res_used));
- if (srp->rq) {
- if (srp->bio)
- ret = blk_rq_unmap_user(srp->bio);
+ if (srp->bio)
+ ret = blk_rq_unmap_user(srp->bio);
+ if (srp->rq) {
if (srp->rq->cmd != srp->rq->__cmd)
kfree(srp->rq->cmd);
blk_put_request(srp->rq);

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