[PATCH v24 30/46] sg: expand sg_comm_wr_t

Douglas Gilbert
2022-04-11T02:32:24Z

The internal struct sg_comm_wr_t was added when the number of
arguments to sg_common_write() became excessive. Expand this idea
so multiple calls to sg_fetch_cmnd() can be deferred until a
scsi_request object is ready to receive the command. This saves
a 252 byte stack allocation on every submit path. Prior to this
and a few other changes, the kernel infrastructure was warning
about excessive stack usage.

Reviewed-by: Hannes Reinecke <hare@suse.com>

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
drivers/scsi/sg.c | 162 ++++++++++++++++++++++++----------------------
1 file changed, 83 insertions(+), 79 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index e8502dd9d6bf..5df79e5fc6d5 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -256,36 +256,38 @@ struct sg_device { /* holds the state of each scsi generic device */

struct sg_comm_wr_t { /* arguments to sg_common_write() */
int timeout;
+ int cmd_len;
unsigned long frq_bm[1]; /* see SG_FRQ_* defines above */
union { /* selector is frq_bm.SG_FRQ_IS_V4I */
struct sg_io_hdr *h3p;
struct sg_io_v4 *h4p;
};
- u8 *cmnd;
+ struct sg_fd *sfp;
+ struct file *filp;
+ const u8 __user *u_cmdp;
};

/* tasklet or soft irq callback */
static void sg_rq_end_io(struct request *rq, blk_status_t status);
/* Declarations of other static functions used before they are defined */
static int sg_proc_init(void);
-static int sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
- struct sg_io_v4 *h4p, int dxfer_dir);
+static int sg_start_req(struct sg_request *srp, struct sg_comm_wr_t *cwrp,
+ int dxfer_dir);
static void sg_finish_scsi_blk_rq(struct sg_request *srp);
static int sg_mk_sgat(struct sg_scatter_hold *schp, struct sg_fd *sfp, int minlen);
static void sg_remove_sgat_helper(struct sg_fd *sfp, struct sg_scatter_hold *schp);
static int sg_v3_submit(struct file *filp, struct sg_fd *sfp,
struct sg_io_hdr *hp, bool sync,
struct sg_request **o_srp);
-static struct sg_request *sg_common_write(struct sg_fd *sfp,
- struct sg_comm_wr_t *cwrp);
+static struct sg_request *sg_common_write(struct sg_comm_wr_t *cwrp);
static int sg_read_append(struct sg_request *srp, void __user *outp,
int num_xfer);
static void sg_remove_sgat(struct sg_request *srp);
static struct sg_fd *sg_add_sfp(struct sg_device *sdp);
static void sg_remove_sfp(struct kref *);
static struct sg_request *sg_find_srp_by_id(struct sg_fd *sfp, int id);
-static struct sg_request *sg_setup_req(struct sg_fd *sfp, int dxfr_len,
- struct sg_comm_wr_t *cwrp);
+static struct sg_request *sg_setup_req(struct sg_comm_wr_t *cwrp,
+ int dxfr_len);
static void sg_deact_request(struct sg_fd *sfp, struct sg_request *srp);
static struct sg_device *sg_get_dev(int min_dev);
static void sg_device_destroy(struct kref *kref);
@@ -571,7 +573,6 @@ sg_write(struct file *filp, const char __user *p, size_t count, loff_t *ppos)
struct sg_device *sdp;
struct sg_fd *sfp;
struct sg_request *srp;
- u8 cmnd[SG_MAX_CDB_SIZE];
struct sg_header ov2hdr;
struct sg_io_hdr v3hdr;
struct sg_header *ohp = &ov2hdr;
@@ -683,9 +684,6 @@ sg_write(struct file *filp, const char __user *p, size_t count, loff_t *ppos)
h3p->flags = input_size; /* structure abuse ... */
h3p->pack_id = ohp->pack_id;
h3p->usr_ptr = NULL;
- cmnd[0] = opcode;
- if (copy_from_user(cmnd + 1, p + 1, cmd_size - 1))
- return -EFAULT;
/*
* SG_DXFER_TO_FROM_DEV is functionally equivalent to SG_DXFER_FROM_DEV,
* but it is possible that the app intended SG_DXFER_TO_DEV, because
@@ -697,13 +695,16 @@ sg_write(struct file *filp, const char __user *p, size_t count, loff_t *ppos)
"%s: data in/out %d/%d bytes for SCSI command 0x%x-- guessing data in;\n"
" program %s not setting count and/or reply_len properly\n",
__func__, ohp->reply_len - (int)SZ_SG_HEADER,
- input_size, (unsigned int)cmnd[0], current->comm);
+ input_size, (unsigned int)opcode, current->comm);
}
- cwr.frq_bm[0] = 0; /* initial state clear for all req flags */
cwr.h3p = h3p;
+ cwr.frq_bm[0] = 0;
cwr.timeout = sfp->timeout;
- cwr.cmnd = cmnd;
- srp = sg_common_write(sfp, &cwr);
+ cwr.cmd_len = cmd_size;
+ cwr.filp = filp;
+ cwr.sfp = sfp;
+ cwr.u_cmdp = p;
+ srp = sg_common_write(&cwr);
return (IS_ERR(srp)) ? PTR_ERR(srp) : (int)count;
}

@@ -745,31 +746,29 @@ static int
sg_v3_submit(struct file *filp, struct sg_fd *sfp, struct sg_io_hdr *hp,
bool sync, struct sg_request **o_srp)
{
- int res, timeout;
unsigned long ul_timeout;
struct sg_request *srp;
struct sg_comm_wr_t cwr;
- u8 cmnd[SG_MAX_CDB_SIZE];

/* now doing v3 blocking (sync) or non-blocking submission */
if (hp->flags & SG_FLAG_MMAP_IO) {
- res = sg_chk_mmap(sfp, hp->flags, hp->dxfer_len);
+ int res = sg_chk_mmap(sfp, hp->flags, hp->dxfer_len);
+
if (res)
return res;
}
/* when v3 seen, allow cmd_q on this fd (def: no cmd_q) */
set_bit(SG_FFD_CMD_Q, sfp->ffd_bm);
ul_timeout = msecs_to_jiffies(hp->timeout);
- timeout = min_t(unsigned long, ul_timeout, INT_MAX);
- res = sg_fetch_cmnd(filp, sfp, hp->cmdp, hp->cmd_len, cmnd);
- if (res)
- return res;
cwr.frq_bm[0] = 0;
__assign_bit(SG_FRQ_SYNC_INVOC, cwr.frq_bm, (int)sync);
cwr.h3p = hp;
- cwr.timeout = timeout;
- cwr.cmnd = cmnd;
- srp = sg_common_write(sfp, &cwr);
+ cwr.timeout = min_t(unsigned long, ul_timeout, INT_MAX);
+ cwr.cmd_len = hp->cmd_len;
+ cwr.filp = filp;
+ cwr.sfp = sfp;
+ cwr.u_cmdp = hp->cmdp;
+ srp = sg_common_write(&cwr);
if (IS_ERR(srp))
return PTR_ERR(srp);
if (o_srp)
@@ -781,11 +780,10 @@ static int
sg_submit_v4(struct file *filp, struct sg_fd *sfp, void __user *p,
struct sg_io_v4 *h4p, bool sync, struct sg_request **o_srp)
{
- int timeout, res;
+ int res = 0;
unsigned long ul_timeout;
struct sg_request *srp;
struct sg_comm_wr_t cwr;
- u8 cmnd[SG_MAX_CDB_SIZE];

if (h4p->flags & SG_FLAG_MMAP_IO) {
int len = 0;
@@ -801,18 +799,16 @@ sg_submit_v4(struct file *filp, struct sg_fd *sfp, void __user *p,
/* once v4 (or v3) seen, allow cmd_q on this fd (def: no cmd_q) */
set_bit(SG_FFD_CMD_Q, sfp->ffd_bm);
ul_timeout = msecs_to_jiffies(h4p->timeout);
- timeout = min_t(unsigned long, ul_timeout, INT_MAX);
- res = sg_fetch_cmnd(filp, sfp, cuptr64(h4p->request), h4p->request_len,
- cmnd);
- if (res)
- return res;
+ cwr.filp = filp;
+ cwr.sfp = sfp;
cwr.frq_bm[0] = 0;
- assign_bit(SG_FRQ_SYNC_INVOC, cwr.frq_bm, (int)sync);
- set_bit(SG_FRQ_IS_V4I, cwr.frq_bm);
+ __assign_bit(SG_FRQ_SYNC_INVOC, cwr.frq_bm, (int)sync);
+ __set_bit(SG_FRQ_IS_V4I, cwr.frq_bm);
cwr.h4p = h4p;
- cwr.timeout = timeout;
- cwr.cmnd = cmnd;
- srp = sg_common_write(sfp, &cwr);
+ cwr.timeout = min_t(unsigned long, ul_timeout, INT_MAX);
+ cwr.cmd_len = h4p->request_len;
+ cwr.u_cmdp = cuptr64(h4p->request);
+ srp = sg_common_write(&cwr);
if (IS_ERR(srp))
return PTR_ERR(srp);
if (o_srp)
@@ -984,13 +980,14 @@ sg_execute_cmd(struct sg_fd *sfp, struct sg_request *srp)
* N.B. pack_id placed in sg_io_v4::request_extra field.
*/
static struct sg_request *
-sg_common_write(struct sg_fd *sfp, struct sg_comm_wr_t *cwrp)
+sg_common_write(struct sg_comm_wr_t *cwrp)
{
int res = 0;
- int dxfr_len, dir, cmd_len;
+ int dxfr_len, dir;
int pack_id = SG_PACK_ID_WILDCARD;
u32 rq_flags;
- struct sg_device *sdp = sfp->parentdp;
+ struct sg_fd *fp = cwrp->sfp;
+ struct sg_device *sdp = fp->parentdp;
struct sg_request *srp;
struct sg_io_hdr *hi_p;
struct sg_io_v4 *h4p;
@@ -1022,40 +1019,36 @@ sg_common_write(struct sg_fd *sfp, struct sg_comm_wr_t *cwrp)
if (dxfr_len >= SZ_256M)
return ERR_PTR(-EINVAL);

- srp = sg_setup_req(sfp, dxfr_len, cwrp);
+ srp = sg_setup_req(cwrp, dxfr_len);
if (IS_ERR(srp))
return srp;
srp->rq_flags = rq_flags;
srp->pack_id = pack_id;

if (h4p) {
- memset(&srp->s_hdr4, 0, sizeof(srp->s_hdr4));
srp->s_hdr4.usr_ptr = h4p->usr_ptr;
srp->s_hdr4.sbp = uptr64(h4p->response);
srp->s_hdr4.max_sb_len = h4p->max_response_len;
srp->s_hdr4.cmd_len = h4p->request_len;
srp->s_hdr4.dir = dir;
- cmd_len = h4p->request_len;
+ srp->s_hdr4.out_resid = 0;
} else { /* v3 interface active */
- cmd_len = hi_p->cmd_len;
memcpy(&srp->s_hdr3, hi_p, sizeof(srp->s_hdr3));
}
- srp->cmd_opcode = cwrp->cmnd[0];/* hold opcode of command for debug */
- SG_LOG(4, sfp, "%s: opcode=0x%02x, cdb_sz=%d, pack_id=%d\n", __func__,
- (int)cwrp->cmnd[0], cmd_len, pack_id);
-
- res = sg_start_req(srp, cwrp->cmnd, cmd_len, h4p, dir);
+ res = sg_start_req(srp, cwrp, dir);
if (res < 0) /* probably out of space --> -ENOMEM */
goto err_out;
+ SG_LOG(4, fp, "%s: opcode=0x%02x, cdb_sz=%d, pack_id=%d\n", __func__,
+ srp->cmd_opcode, cwrp->cmd_len, pack_id);
if (unlikely(SG_IS_DETACHING(sdp))) {
res = -ENODEV;
goto err_out;
}
srp->rq->timeout = cwrp->timeout;
- sg_execute_cmd(sfp, srp);
+ sg_execute_cmd(fp, srp);
return srp;
err_out:
- sg_deact_request(sfp, srp);
+ sg_deact_request(fp, srp);
return ERR_PTR(res);
}

@@ -1272,8 +1265,8 @@ sg_ctl_ioreceive(struct file *filp, struct sg_fd *sfp, void __user *p)
id));
if (unlikely(SG_IS_DETACHING(sdp)))
return -ENODEV;
- if (res) /* -ERESTARTSYS as signal hit process */
- return res;
+ if (res)
+ return res; /* signal --> -ERESTARTSYS */
} /* now srp should be valid */
return sg_receive_v4(sfp, srp, p, h4p);
}
@@ -2645,7 +2638,7 @@ init_sg(void)
}
sg_sysfs_valid = true;
rc = scsi_register_interface(&sg_interface);
- if (0 == rc) {
+ if (rc == 0) {
sg_proc_init();
return 0;
}
@@ -2696,11 +2689,10 @@ sg_chk_dio_allowed(struct sg_device *sdp, struct sg_request *srp,
return false;
}

-static void
+static inline void
sg_set_map_data(const struct sg_scatter_hold *schp, bool up_valid,
struct rq_map_data *mdp)
{
- memset(mdp, 0, sizeof(*mdp));
mdp->pages = schp->pages;
mdp->page_order = schp->page_order;
mdp->nr_entries = schp->num_sgat;
@@ -2709,8 +2701,7 @@ sg_set_map_data(const struct sg_scatter_hold *schp, bool up_valid,
}

static int
-sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
- struct sg_io_v4 *h4p, int dxfer_dir)
+sg_start_req(struct sg_request *srp, struct sg_comm_wr_t *cwrp, int dxfer_dir)
{
bool reserved, us_xfer;
int res = 0;
@@ -2720,7 +2711,7 @@ sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
void __user *up;
struct request *rq;
struct scsi_cmnd *scmd;
- struct sg_fd *sfp = srp->parentfp;
+ struct sg_fd *sfp = cwrp->sfp;
struct sg_device *sdp;
struct sg_scatter_hold *req_schp;
struct request_queue *q;
@@ -2729,7 +2720,9 @@ sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
struct rq_map_data map_data;

sdp = sfp->parentdp;
- if (h4p) {
+ if (test_bit(SG_FRQ_IS_V4I, srp->frq_bm)) {
+ struct sg_io_v4 *h4p = cwrp->h4p;
+
if (dxfer_dir == SG_DXFER_TO_DEV) {
r0w = WRITE;
up = uptr64(h4p->dout_xferp);
@@ -2772,8 +2765,15 @@ sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
scmd = blk_mq_rq_to_pdu(rq);
srp->rq = rq;

- memcpy(scmd->cmnd, cmd, cmd_len);
- scmd->cmd_len = cmd_len;
+ if (cwrp->u_cmdp)
+ res = sg_fetch_cmnd(cwrp->filp, sfp, cwrp->u_cmdp,
+ cwrp->cmd_len, scmd->cmnd);
+ else
+ res = -EPROTO;
+ if (res)
+ goto fini;
+ scmd->cmd_len = cwrp->cmd_len;
+ srp->cmd_opcode = scmd->cmnd[0];
us_xfer = !(srp->rq_flags & SG_FLAG_NO_DXFER);
assign_bit(SG_FRQ_NO_US_XFER, srp->frq_bm, !us_xfer);
reserved = (sfp->rsv_srp == srp);
@@ -2796,7 +2796,7 @@ sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,
}

if (likely(md)) { /* normal, "indirect" IO */
- if (unlikely((srp->rq_flags & SG_FLAG_MMAP_IO))) {
+ if (unlikely(srp->rq_flags & SG_FLAG_MMAP_IO)) {
/* mmap IO must use and fit in reserve request */
if (!reserved || dxfer_len > req_schp->buflen)
res = reserved ? -ENOMEM : -EBUSY;
@@ -2805,7 +2805,7 @@ sg_start_req(struct sg_request *srp, u8 *cmd, int cmd_len,

res = sg_mk_sgat(&srp->sgat_h, sfp, up_sz);
}
- if (res)
+ if (unlikely(res))
goto fini;

sg_set_map_data(req_schp, !!up, md);
@@ -3133,7 +3133,7 @@ sg_mk_srp_sgat(struct sg_fd *sfp, bool first, int db_len)
return n_srp;
if (db_len > 0) {
res = sg_mk_sgat(&n_srp->sgat_h, sfp, db_len);
- if (res) {
+ if (unlikely(res)) {
kfree(n_srp);
return ERR_PTR(res);
}
@@ -3186,18 +3186,18 @@ sg_build_reserve(struct sg_fd *sfp, int buflen)
* failure returns a negated errno value twisted by ERR_PTR() macro.
*/
static struct sg_request *
-sg_setup_req(struct sg_fd *sfp, int dxfr_len, struct sg_comm_wr_t *cwrp)
+sg_setup_req(struct sg_comm_wr_t *cwrp, int dxfr_len)
{
bool act_empty = false;
bool found = false;
- bool mk_new_srp = false;
+ bool mk_new_srp = true;
bool try_harder = false;
- int res;
int num_inactive = 0;
unsigned long idx, last_idx, iflags;
+ struct sg_fd *fp = cwrp->sfp;
struct sg_request *r_srp = NULL; /* request to return */
struct sg_request *last_srp = NULL;
- struct xarray *xafp = &sfp->srp_arr;
+ struct xarray *xafp = &fp->srp_arr;
__maybe_unused const char *cp;

start_again:
@@ -3250,18 +3250,19 @@ sg_setup_req(struct sg_fd *sfp, int dxfr_len, struct sg_comm_wr_t *cwrp)
mk_new_srp = true;
}
if (mk_new_srp) {
- bool allow_cmd_q = test_bit(SG_FFD_CMD_Q, sfp->ffd_bm);
+ bool allow_cmd_q = test_bit(SG_FFD_CMD_Q, fp->ffd_bm);
+ int res;
u32 n_idx;
struct xa_limit xal = { .max = 0, .min = 0 };

cp = "new";
- if (!allow_cmd_q && atomic_read(&sfp->submitted) > 0) {
+ if (!allow_cmd_q && atomic_read(&fp->submitted) > 0) {
r_srp = ERR_PTR(-EDOM);
- SG_LOG(6, sfp, "%s: trying 2nd req but cmd_q=false\n",
+ SG_LOG(6, fp, "%s: trying 2nd req but cmd_q=false\n",
__func__);
goto fini;
}
- r_srp = sg_mk_srp_sgat(sfp, act_empty, dxfr_len);
+ r_srp = sg_mk_srp_sgat(fp, act_empty, dxfr_len);
if (IS_ERR(r_srp)) {
if (!try_harder && dxfr_len < SG_DEF_SECTOR_SZ &&
num_inactive > 0) {
@@ -3272,11 +3273,11 @@ sg_setup_req(struct sg_fd *sfp, int dxfr_len, struct sg_comm_wr_t *cwrp)
}
atomic_set(&r_srp->rq_st, SG_RS_BUSY);
xa_lock_irqsave(xafp, iflags);
- xal.max = atomic_inc_return(&sfp->req_cnt);
+ xal.max = atomic_inc_return(&fp->req_cnt);
res = __xa_alloc(xafp, &n_idx, r_srp, xal, GFP_KERNEL);
xa_unlock_irqrestore(xafp, iflags);
if (res < 0) {
- SG_LOG(1, sfp, "%s: xa_alloc() failed, errno=%d\n",
+ SG_LOG(1, fp, "%s: xa_alloc() failed, errno=%d\n",
__func__, -res);
sg_remove_sgat(r_srp);
kfree(r_srp);
@@ -3285,17 +3286,18 @@ sg_setup_req(struct sg_fd *sfp, int dxfr_len, struct sg_comm_wr_t *cwrp)
}
idx = n_idx;
r_srp->rq_idx = idx;
- r_srp->parentfp = sfp;
- SG_LOG(4, sfp, "%s: mk_new_srp=0x%pK ++\n", __func__, r_srp);
+ r_srp->parentfp = fp;
+ SG_LOG(4, fp, "%s: mk_new_srp=0x%pK ++\n", __func__, r_srp);
}
r_srp->frq_bm[0] = cwrp->frq_bm[0]; /* assumes <= 32 req flags */
r_srp->sgat_h.dlen = dxfr_len;/* must be <= r_srp->sgat_h.buflen */
r_srp->cmd_opcode = 0xff; /* set invalid opcode (VS), 0x0 is TUR */
fini:
if (IS_ERR(r_srp))
- SG_LOG(1, sfp, "%s: err=%ld\n", __func__, PTR_ERR(r_srp));
+ SG_LOG(1, fp, "%s: err=%ld\n", __func__, PTR_ERR(r_srp));
if (!IS_ERR(r_srp))
- SG_LOG(4, sfp, "%s: %s r_srp=0x%pK\n", __func__, cp, r_srp);
+ SG_LOG(4, fp, "%s: %s %sr_srp=0x%pK\n", __func__, cp,
+ ((r_srp == fp->rsv_srp) ? "[rsv] " : ""), r_srp);
return r_srp;
}

@@ -3350,6 +3352,8 @@ sg_add_sfp(struct sg_device *sdp)
__assign_bit(SG_FFD_CMD_Q, sfp->ffd_bm, SG_DEF_COMMAND_Q);
__assign_bit(SG_FFD_KEEP_ORPHAN, sfp->ffd_bm, SG_DEF_KEEP_ORPHAN);
__assign_bit(SG_FFD_Q_AT_TAIL, sfp->ffd_bm, SG_DEFAULT_Q_AT);
+ atomic_set(&sfp->submitted, 0);
+ atomic_set(&sfp->waiting, 0);
/*
* SG_SCATTER_SZ initializes scatter_elem_sz but different value may
* be given as driver/module parameter (e.g. 'scatter_elem_sz=8192').
--
2.25.1