Replace the linked list and the fix arrays of requests (max 16)
with an xarray. The xarray (srp_arr) has two marks: one for
INACTIVE state (i.e. available for re-use) requests; the other
is AWAIT state which is after the internal completion point of
a request and before the user space has fetched the response.
Of the five states in sg_request::rq_st, two are marked. They are
SG_RS_INACTIVE and SG_RS_AWAIT_RCV. This allows the request xarray
(sg_fd::srp_arr) to be searched (with xa_for_each_mark) on two
embedded sub-lists. The SG_RS_INACTIVE sub-list replaces the free
list. The SG_RS_AWAIT_RCV sub-list contains requests that have
reached their internal completion point but have not been read/
received by the user space. Add support functions for this and
partially wire them up.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/sg.c | 325 +++++++++++++++++++++++++++++++++-------------
1 file changed, 238 insertions(+), 87 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index de4b35aabe40..ef3674b9a5dc 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -73,7 +73,7 @@ static char *sg_version_date = "20190606";
#define SG_MAX_CDB_SIZE 252
/* Following enum contains the states of sg_request::rq_st */
-enum sg_rq_state {
+enum sg_rq_state { /* N.B. sg_rq_state_arr assumes SG_RS_AWAIT_RCV==2 */
SG_RS_INACTIVE = 0, /* request not in use (e.g. on fl) */
SG_RS_INFLIGHT, /* active: cmd/req issued, no response yet */
SG_RS_AWAIT_RCV, /* have response from LLD, awaiting receive */
@@ -115,6 +115,11 @@ enum sg_rq_state {
#define SG_FDEV_DETACHING 1 /* may be unexpected device removal */
#define SG_FDEV_LOG_SENSE 2 /* set by ioctl(SG_SET_DEBUG) */
+/* xarray 'mark's allow sub-lists within main array/list. */
+#define SG_XA_RQ_FREE XA_MARK_0 /* xarray sets+clears */
+#define SG_XA_RQ_INACTIVE XA_MARK_1
+#define SG_XA_RQ_AWAIT XA_MARK_2
+
int sg_big_buff = SG_DEF_RESERVED_SIZE;
/*
* This variable is accessible via /proc/scsi/sg/def_reserved_size . Each
@@ -154,11 +159,11 @@ struct sg_device; /* forward declarations */
struct sg_fd;
struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */
- struct list_head entry; /* list entry */
struct sg_scatter_hold data; /* hold buffer, perhaps scatter list */
struct sg_io_hdr header; /* scsi command+info, see <scsi/sg.h> */
u8 sense_b[SCSI_SENSE_BUFFERSIZE];
u32 duration; /* cmd duration in milliseconds */
+ u32 rq_idx; /* my index within parent's srp_arr */
char res_used; /* 1 -> using reserve buffer, 0 -> not ... */
char orphan; /* 1 -> drop on sight, 0 -> normal */
u32 rq_result; /* packed scsi request result from LLD */
@@ -177,24 +182,23 @@ struct sg_request { /* SG_MAX_QUEUE requests
outstanding per file */
struct sg_fd { /* holds the state of a file descriptor */
struct sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
- spinlock_t rq_list_lock; /* protect access to list in req_arr */
struct mutex f_mutex; /* protect against changes in this fd */
int timeout; /* defaults to SG_DEFAULT_TIMEOUT */
int timeout_user; /* defaults to SG_DEFAULT_TIMEOUT_USER */
u32 idx; /* my index within parent's sfp_arr */
- atomic_t submitted; /* number inflight or awaiting read */
- atomic_t waiting; /* number of requests awaiting read */
+ atomic_t submitted; /* number inflight or awaiting receive */
+ atomic_t waiting; /* number of requests awaiting receive */
+ atomic_t req_cnt; /* number of requests */
int sgat_elem_sz; /* initialized to scatter_elem_sz */
struct sg_scatter_hold reserve; /* buffer for this file descriptor */
- struct list_head rq_list; /* head of request list */
- struct fasync_struct *async_qp; /* used by asynchronous notification */
- struct sg_request req_arr[SG_MAX_QUEUE];/* use as singly-linked list */
char force_packid; /* 1 -> pack_id input to read(), 0 -> ignored */
char cmd_q; /* 1 -> allow command queuing, 0 -> don't */
u8 next_cmd_len; /* 0: automatic, >0: use on next write() */
char keep_orphan; /* 0 -> drop orphan (def), 1 -> keep for read() */
char mmap_called; /* 0 -> mmap() never called on this fd */
char res_in_use; /* 1 -> 'reserve' array in use */
+ struct fasync_struct *async_qp; /* used by asynchronous notification */
+ struct xarray srp_arr;
struct kref f_ref;
struct execute_work ew_fd; /* harvest all fd resources and lists */
};
@@ -273,6 +277,7 @@ static const char *sg_rq_st_str(enum sg_rq_state rq_st,
bool long_str);
#if IS_ENABLED(CONFIG_SCSI_LOGGING) && IS_ENABLED(SG_DEBUG)
#define SG_LOG_BUFF_SZ 48
+#define SG_LOG_ACTIVE 1
#define SG_LOG(depth, sfp, fmt, a...) \
do { \
@@ -724,6 +729,119 @@ sg_submit(struct sg_fd *sfp, struct file *filp, const
char __user *buf,
return count;
}
+#if IS_ENABLED(SG_LOG_ACTIVE)
+static void
+sg_rq_state_fail(struct sg_fd *sfp, enum sg_rq_state exp_old_st,
+ enum sg_rq_state want_st, enum sg_rq_state act_old_st,
+ const char *fromp)
+{
+ const char *eaw_rs = "expected_old,actual_old,wanted rq_st";
+
+ if (IS_ENABLED(CONFIG_SCSI_PROC_FS))
+ SG_LOG(1, sfp, "%s: %s: %s: %s,%s,%s\n",
+ __func__, fromp, eaw_rs,
+ sg_rq_st_str(exp_old_st, false),
+ sg_rq_st_str(act_old_st, false),
+ sg_rq_st_str(want_st, false));
+ else
+ pr_info("sg: %s: %s: %s: %d,%d,%d\n", __func__, fromp, eaw_rs,
+ (int)exp_old_st, (int)act_old_st, (int)want_st);
+}
+#endif
+
+static void
+sg_rq_state_force(struct sg_request *srp, enum sg_rq_state new_st)
+{
+ bool prev, want;
+ struct xarray *xafp = &srp->parentfp->srp_arr;
+
+ atomic_set(&srp->rq_st, new_st);
+ want = (new_st == SG_RS_AWAIT_RCV);
+ prev = xa_get_mark(xafp, srp->rq_idx, SG_XA_RQ_AWAIT);
+ if (prev != want) {
+ if (want)
+ __xa_set_mark(xafp, srp->rq_idx, SG_XA_RQ_AWAIT);
+ else
+ __xa_clear_mark(xafp, srp->rq_idx, SG_XA_RQ_AWAIT);
+ }
+ want = (new_st == SG_RS_INACTIVE);
+ prev = xa_get_mark(xafp, srp->rq_idx, SG_XA_RQ_INACTIVE);
+ if (prev != want) {
+ if (want)
+ __xa_set_mark(xafp, srp->rq_idx, SG_XA_RQ_INACTIVE);
+ else
+ __xa_clear_mark(xafp, srp->rq_idx, SG_XA_RQ_INACTIVE);
+ }
+}
+
+/* Following array indexed by enum sg_rq_state, 0 means no xa mark change */
+static int sg_rq_state_arr[] = {1, 0, 4, 0, 0};
+
+static void
+sg_rq_state_helper(struct sg_request *srp, enum sg_rq_state old_st,
+ enum sg_rq_state new_st)
+{
+ int indic = sg_rq_state_arr[(int)old_st] +
+ (sg_rq_state_arr[(int)new_st] << 1);
+ struct xarray *xafp = &srp->parentfp->srp_arr;
+
+ if (indic == 0)
+ return;
+ if (indic & 1) /* from inactive state */
+ __xa_clear_mark(xafp, srp->rq_idx, SG_XA_RQ_INACTIVE);
+ else if (indic & 2) /* to inactive state */
+ __xa_set_mark(xafp, srp->rq_idx, SG_XA_RQ_INACTIVE);
+ if ((indic & (4 | 8)) == 0)
+ return;
+ if (test_bit(SG_FRQ_SYNC_INVOC, srp->frq_bm))
+ return; /* skip AWAIT mark for sync invocations */
+ if (indic & 4) /* from await state */
+ __xa_clear_mark(xafp, srp->rq_idx, SG_XA_RQ_AWAIT);
+ else if (indic & 8) /* to await state */
+ __xa_set_mark(xafp, srp->rq_idx, SG_XA_RQ_AWAIT);
+}
+
+/*
+ * This function keeps the srp->rq_st state and associated marks on the
+ * owning xarray's element in sync. If force is true then new_st is stored
+ * in srp->rq_st and xarray marks are set accordingly (and old_st is
+ * ignored); and 0 is returned.
+ * If force is false, then atomic_cmpxchg() is called. If the actual
+ * srp->rq_st is not old_st, then -EPROTOTYPE is returned. If the actual
+ * srp->rq_st is old_st then it is replaced by new_st and the xarray marks
+ * are setup accordingly and 0 is returned. This assumes srp_arr xarray
+ * spinlock is held.
+ */
+static int
+sg_rq_state_chg(struct sg_request *srp, enum sg_rq_state old_st,
+ enum sg_rq_state new_st, bool force, const char *fromp)
+{
+ unsigned long iflags;
+ enum sg_rq_state act_old_st;
+ struct xarray *xafp = &srp->parentfp->srp_arr;
+
+ if (force) {
+ xa_lock_irqsave(xafp, iflags);
+ sg_rq_state_force(srp, new_st);
+ xa_unlock_irqrestore(xafp, iflags);
+ return 0;
+ }
+ act_old_st = (enum sg_rq_state)atomic_cmpxchg(&srp->rq_st, old_st,
+ new_st);
+ if (act_old_st != old_st) {
+#if IS_ENABLED(SG_LOG_ACTIVE)
+ if (fromp)
+ sg_rq_state_fail(srp->parentfp, old_st, new_st,
+ act_old_st, fromp);
+#endif
+ return -EPROTOTYPE; /* only used for this error type */
+ }
+ xa_lock_irqsave(xafp, iflags);
+ sg_rq_state_helper(srp, old_st, new_st);
+ xa_unlock_irqrestore(xafp, iflags);
+ return 0;
+}
