[PATCH v5 16/23] sg: rework sg_vma_fault

[Douglas Gilbert <dgilbert@xxxxxxxxxxxx>]

Simple refactoring of the sg_vma_fault() function.

Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
 drivers/scsi/sg.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 903faafaeff9..befcbfbcece1 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1389,14 +1389,16 @@ sg_fasync(int fd, struct file *filp, int mode)
 	return fasync_helper(fd, filp, mode, &sfp->async_qp);
 }
 
+/* Note: the error return: VM_FAULT_SIGBUS causes a "bus error" */
 static vm_fault_t
 sg_vma_fault(struct vm_fault *vmf)
 {
-	struct vm_area_struct *vma = vmf->vma;
-	struct sg_fd *sfp;
+	int k, length;
 	unsigned long offset, len, sa;
+	struct vm_area_struct *vma = vmf->vma;
 	struct sg_scatter_hold *rsv_schp;
-	int k, length;
+	struct sg_device *sdp;
+	struct sg_fd *sfp;
 	const char *nbp = "==NULL, bad";
 
 	if (!vma) {
@@ -1408,20 +1410,31 @@ sg_vma_fault(struct vm_fault *vmf)
 		pr_warn("%s: sfp%s\n", __func__, nbp);
 		goto out_err;
 	}
+	sdp = sfp->parentdp;
+	if (sdp && unlikely(SG_IS_DETACHING(sdp))) {
+		SG_LOG(1, sfp, "%s: device detaching\n", __func__);
+		goto out_err;
+	}
 	rsv_schp = &sfp->reserve;
 	offset = vmf->pgoff << PAGE_SHIFT;
-	if (offset >= rsv_schp->buflen)
-		return VM_FAULT_SIGBUS;
+	if (offset >= (unsigned int)rsv_schp->buflen) {
+		SG_LOG(1, sfp, "%s: offset[%lu] >= rsv.buflen\n", __func__,
+		       offset);
+		goto out_err;
+	}
 	sa = vma->vm_start;
 	SG_LOG(3, sfp, "%s: vm_start=0x%lx, off=%lu\n", __func__, sa, offset);
 	length = 1 << (PAGE_SHIFT + rsv_schp->page_order);
-	for (k = 0; k < rsv_schp->num_sgat && sa < vma->vm_end; k++) {
+	for (k = 0; k < rsv_schp->num_sgat && sa < vma->vm_end; ++k) {
 		len = vma->vm_end - sa;
-		len = (len < length) ? len : length;
+		len = min_t(int, len, (int)length);
 		if (offset < len) {
-			struct page *page = nth_page(rsv_schp->pages[k],
-						     offset >> PAGE_SHIFT);
-			get_page(page);	/* increment page count */
+			struct page *page;
+			struct page *pp;
+
+			pp = rsv_schp->pages[k];
+			page = nth_page(pp, offset >> PAGE_SHIFT);
+			get_page(page); /* increment page count */
 			vmf->page = page;
 			return 0; /* success */
 		}
-- 
2.23.0