diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index c014fb24eca17f..64e9de67ccd487 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -88,7 +88,11 @@ enum sg_rq_state {
 	SG_RS_BUSY,		/* temporary state should rarely be seen */
 };
 
+/* If sum_of(dlen) of a fd exceeds this, write() will yield E2BIG */
+#define SG_TOT_FD_THRESHOLD (32 * 1024 * 1024)
+
 #define SG_TIME_UNIT_MS 0	/* milliseconds */
+/* #define SG_TIME_UNIT_NS 1	   nanoseconds */
 #define SG_DEF_TIME_UNIT SG_TIME_UNIT_MS
 #define SG_DEFAULT_TIMEOUT mult_frac(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ)
 #define SG_FD_Q_AT_HEAD 0
@@ -223,7 +227,9 @@ struct sg_fd {		/* holds the state of a file descriptor */
 	struct list_head rq_fl; /* head of sg_request free list */
 	int timeout;		/* defaults to SG_DEFAULT_TIMEOUT      */
 	int timeout_user;	/* defaults to SG_DEFAULT_TIMEOUT_USER */
+	int tot_fd_thresh;      /* E2BIG if sum_of(dlen) > this, 0: ignore */
 	int sgat_elem_sz;	/* initialized to scatter_elem_sz */
+	atomic_t sum_fd_dlens;	/* when tot_fd_thresh>0 this is sum_of(dlen) */
 	atomic_t submitted;	/* number inflight or awaiting read */
 	atomic_t waiting;	/* number of requests awaiting read */
 	unsigned long ffd_bm[1];	/* see SG_FFD_* defines above */
@@ -1939,8 +1945,8 @@ sg_ctl_extended(struct sg_fd *sfp, void __user *p)
 {
 	int result = 0;
 	int ret = 0;
-	int s_wr_mask, s_rd_mask;
-	u32 or_masks;
+	int n, j, s_wr_mask, s_rd_mask;
+	u32 uv, or_masks;
 	struct sg_device *sdp = sfp->parentdp;
 	struct sg_extended_info *seip;
 	struct sg_extended_info sei;
@@ -1957,6 +1963,17 @@ sg_ctl_extended(struct sg_fd *sfp, void __user *p)
 	}
 	SG_LOG(3, sdp, "%s: wr_mask=0x%x rd_mask=0x%x\n", __func__, s_wr_mask,
 	       s_rd_mask);
+	/* tot_fd_thresh (u32), [raw] [sum of active cmd dlen_s] */
+	if (or_masks & SG_SEIM_TOT_FD_THRESH) {
+		if (s_wr_mask & SG_SEIM_TOT_FD_THRESH) {
+			uv = seip->tot_fd_thresh;
+			if (uv > 0 && uv < PAGE_SIZE)
+				uv = PAGE_SIZE;
+			sfp->tot_fd_thresh = uv;
+		}
+		if (s_rd_mask & SG_SEIM_TOT_FD_THRESH)
+			seip->tot_fd_thresh = sfp->tot_fd_thresh;
+	}
 	/* check all boolean flags for either wr or rd mask set in or_mask */
 	if (or_masks & SG_SEIM_CTL_FLAGS)
 		sg_extended_bool_flags(sfp, seip);
@@ -1971,6 +1988,23 @@ sg_ctl_extended(struct sg_fd *sfp, void __user *p)
 	}
 	if ((s_rd_mask & SG_SEIM_READ_VAL) && (s_wr_mask & SG_SEIM_READ_VAL))
 		sg_extended_read_value(sfp, seip);
+	/* override scatter gather element size [rbw] (def: SG_SCATTER_SZ) */
+	if (or_masks & SG_SEIM_SGAT_ELEM_SZ) {
+		n = sfp->sgat_elem_sz;
+		if (s_wr_mask & SG_SEIM_SGAT_ELEM_SZ) {
+			j = (int)seip->sgat_elem_sz;
+			if (j != (1 << ilog2(j)) || j < (int)PAGE_SIZE) {
+				SG_LOG(1, sdp, "%s: %s not power of 2, %s\n",
+				       __func__, "sgat element size",
+				       "or less than PAGE_SIZE");
+				ret = -EINVAL;
+			} else {
+				sfp->sgat_elem_sz = j;
+			}
+		}
+		if (s_rd_mask & SG_SEIM_SGAT_ELEM_SZ)
+			seip->sgat_elem_sz = n; /* prior value if rw */
+	}
 	/* reserved_sz [raw], since may be reduced by other limits */
 	if (s_wr_mask & SG_SEIM_RESERVED_SIZE) {
 		mutex_lock(&sfp->f_mutex);
@@ -3289,6 +3323,8 @@ sg_mk_sgat(struct sg_request *srp, struct sg_fd *sfp, int minlen)
 	if (unlikely(rem_sz > 0))       /* must have failed */
 		return -ENOMEM;
 	schp->buflen = align_sz;
+	if (sfp->tot_fd_thresh > 0)
+		atomic_add(align_sz, &sfp->sum_fd_dlens);
 	return 0;
 err_out:
 	for (j = 0; j < k; ++j)
@@ -3335,6 +3371,15 @@ sg_remove_sgat(struct sg_request *srp)
 	if (!test_bit(SG_FRQ_DIO_IN_USE, srp->frq_bm))
 		sg_remove_sgat_helper(sdp, schp);
 
+	if (sfp->tot_fd_thresh > 0) {
+		/* this is a subtraction, error if it goes negative */
+		if (atomic_add_negative(-schp->buflen, &sfp->sum_fd_dlens)) {
+			SG_LOG(2, sfp->parentdp,
+			       "%s: logic error: this dlen > %s\n",
+			       __func__, "sum_fd_dlens");
+			atomic_set(&sfp->sum_fd_dlens, 0);
+		}
+	}
 	memset(schp, 0, sizeof(*schp));         /* zeros buflen and dlen */
 }
 
@@ -3560,6 +3605,7 @@ sg_add_request(struct sg_comm_wr_t *cwrp, int dxfr_len)
 {
 	bool act_empty = false;
 	bool mk_new_srp = true;
+	u32 sum_dlen;
 	unsigned long iflags;
 	enum sg_rq_state sr_st;
 	struct sg_fd *fp = cwrp->sfp;
@@ -3613,6 +3659,13 @@ sg_add_request(struct sg_comm_wr_t *cwrp, int dxfr_len)
 			r_srp = ERR_PTR(-EDOM);
 			SG_LOG(6, sdp, "%s: trying 2nd req but cmd_q=false\n",
 			       __func__);
+		} else if (fp->tot_fd_thresh > 0) {
+			sum_dlen = atomic_read(&fp->sum_fd_dlens) + dxfr_len;
+			if (sum_dlen > (u32)fp->tot_fd_thresh) {
+				r_srp = ERR_PTR(-E2BIG);
+				SG_LOG(2, sdp, "%s: sum_of_dlen(%u) > %s\n",
+				       __func__, sum_dlen, "tot_fd_thresh");
+			}
 		}
 		spin_unlock_irqrestore(&fp->rq_list_lock, iflags);
 		if (IS_ERR(r_srp))        /* NULL is not an ERR here */
@@ -3742,6 +3795,8 @@ sg_add_sfp(struct sg_device *sdp)
 	assign_bit(SG_FFD_KEEP_ORPHAN, sfp->ffd_bm, SG_DEF_KEEP_ORPHAN);
 	assign_bit(SG_FFD_TIME_IN_NS, sfp->ffd_bm, SG_DEF_TIME_UNIT);
 	assign_bit(SG_FFD_Q_AT_TAIL, sfp->ffd_bm, SG_DEFAULT_Q_AT);
+	sfp->tot_fd_thresh = SG_TOT_FD_THRESHOLD;
+	atomic_set(&sfp->sum_fd_dlens, 0);
 	atomic_set(&sfp->submitted, 0);
 	atomic_set(&sfp->waiting, 0);
 	/*
@@ -4237,8 +4292,9 @@ sg_proc_dbg_fd(struct sg_fd *fp, char *obp, int len)
 		       (int)test_bit(SG_FFD_FORCE_PACKID, fp->ffd_bm),
 		       (int)test_bit(SG_FFD_KEEP_ORPHAN, fp->ffd_bm),
 		       fp->ffd_bm[0]);
-	n += scnprintf(obp + n, len - n, "   mmap_called=%d\n",
-		       test_bit(SG_FFD_MMAP_CALLED, fp->ffd_bm));
+	n += scnprintf(obp + n, len - n, "   mmap_called=%d sum_fd_dlens=%u\n",
+		       test_bit(SG_FFD_MMAP_CALLED, fp->ffd_bm),
+		       atomic_read(&fp->sum_fd_dlens));
 	n += scnprintf(obp + n, len - n,
 		       "   submitted=%d waiting=%d   open thr_id=%d\n",
 		       atomic_read(&fp->submitted),
diff --git a/include/uapi/scsi/sg.h b/include/uapi/scsi/sg.h
index ca2b4819ddcd61..378cf0532756ba 100644
--- a/include/uapi/scsi/sg.h
+++ b/include/uapi/scsi/sg.h
@@ -167,6 +167,7 @@ typedef struct sg_req_info {	/* used by SG_GET_REQUEST_TABLE ioctl() */
 #define SG_SEIM_CTL_FLAGS	0x1	/* ctl_flags_mask bits in ctl_flags */
 #define SG_SEIM_READ_VAL	0x2	/* write SG_SEIRV_*, read back value */
 #define SG_SEIM_RESERVED_SIZE	0x4	/* reserved_sz of reserve request */
+#define SG_SEIM_TOT_FD_THRESH	0x8	/* tot_fd_thresh of data buffers */
 #define SG_SEIM_MINOR_INDEX	0x10	/* sg device minor index number */
 #define SG_SEIM_SGAT_ELEM_SZ	0x80	/* sgat element size (>= PAGE_SIZE) */
 #define SG_SEIM_ALL_BITS	0xff	/* should be OR of previous items */