[PATCH v5 17/23] sg: rework sg_mmap

[Douglas Gilbert]

Simple rework of the sg_mmap() function.

Signed-off-by: Douglas Gilbert <dgilb...@interlog.com>
---
 drivers/scsi/sg.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index befcbfbcece1..2ad86aaaf74d 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1449,14 +1449,15 @@ static const struct vm_operations_struct sg_mmap_vm_ops 
= {
        .fault = sg_vma_fault,
 };
 
+/* Entry point for mmap(2) system call */
 static int
 sg_mmap(struct file *filp, struct vm_area_struct *vma)
 {
-       struct sg_fd *sfp;
-       unsigned long req_sz, len, sa;
-       struct sg_scatter_hold *rsv_schp;
        int k, length;
        int ret = 0;
+       unsigned long req_sz, len, sa;
+       struct sg_scatter_hold *rsv_schp;
+       struct sg_fd *sfp;
 
        if (!filp || !vma)
                return -ENXIO;
@@ -1469,19 +1470,23 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
        SG_LOG(3, sfp, "%s: vm_start=%p, len=%d\n", __func__,
               (void *)vma->vm_start, (int)req_sz);
        if (vma->vm_pgoff)
-               return -EINVAL; /* want no offset */
-       rsv_schp = &sfp->reserve;
+               return -EINVAL; /* only an offset of 0 accepted */
+       /* Check reserve request is inactive and has large enough buffer */
        mutex_lock(&sfp->f_mutex);
-       if (req_sz > rsv_schp->buflen) {
-               ret = -ENOMEM;  /* cannot map more than reserved buffer */
+       if (sfp->res_in_use) {
+               ret = -EBUSY;
+               goto out;
+       }
+       rsv_schp = &sfp->reserve;
+       if (req_sz > (unsigned long)rsv_schp->buflen) {
+               ret = -ENOMEM;
                goto out;
        }
-
        sa = vma->vm_start;
        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(unsigned long, len, (unsigned long)length);
                sa += len;
        }
 
-- 
2.23.0