blkcg: restructure blkio_group configruation setting

As part of userland interface restructuring, this patch updates
per-blkio_group configuration setting.  Instead of funneling
everything through a master function which has hard-coded cases for
each config file it may handle, the common part is factored into
blkg_conf_prep() and blkg_conf_finish() and different configuration
setters are implemented using the helpers.

While this doesn't result in immediate LOC reduction, this enables
further cleanups and more modular implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 147 insertions, 140 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index a9723a8dc983..1e1ee2af7b5f 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -43,12 +43,6 @@ EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
 static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
 
-/* for encoding cft->private value on file */
-#define BLKIOFILE_PRIVATE(x, val)       (((x) << 16) | (val))
-/* What policy owns the file, proportional or throttle */
-#define BLKIOFILE_POLICY(val)           (((val) >> 16) & 0xffff)
-#define BLKIOFILE_ATTR(val)             ((val) & 0xffff)
-
 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 {
         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
@@ -86,7 +80,7 @@ static inline void blkio_update_group_weight(struct blkio_group *blkg,
 }
 
 static inline void blkio_update_group_bps(struct blkio_group *blkg, int plid,
-                                          u64 bps, int fileid)
+                                          u64 bps, int rw)
 {
         struct blkio_policy_type *blkiop;
 
@@ -96,21 +90,18 @@ static inline void blkio_update_group_bps(struct blkio_group *blkg, int plid,
                 if (blkiop->plid != plid)
                         continue;
 
-                if (fileid == BLKIO_THROTL_read_bps_device
-                    && blkiop->ops.blkio_update_group_read_bps_fn)
+                if (rw == READ && blkiop->ops.blkio_update_group_read_bps_fn)
                         blkiop->ops.blkio_update_group_read_bps_fn(blkg->q,
                                                                 blkg, bps);
 
-                if (fileid == BLKIO_THROTL_write_bps_device
-                    && blkiop->ops.blkio_update_group_write_bps_fn)
+                if (rw == WRITE && blkiop->ops.blkio_update_group_write_bps_fn)
                         blkiop->ops.blkio_update_group_write_bps_fn(blkg->q,
                                                                 blkg, bps);
         }
 }
 
-static inline void blkio_update_group_iops(struct blkio_group *blkg,
-                                           int plid, unsigned int iops,
-                                           int fileid)
+static inline void blkio_update_group_iops(struct blkio_group *blkg, int plid,
+                                           u64 iops, int rw)
 {
         struct blkio_policy_type *blkiop;
 
@@ -120,13 +111,11 @@ static inline void blkio_update_group_iops(struct blkio_group *blkg,
                 if (blkiop->plid != plid)
                         continue;
 
-                if (fileid == BLKIO_THROTL_read_iops_device
-                    && blkiop->ops.blkio_update_group_read_iops_fn)
+                if (rw == READ && blkiop->ops.blkio_update_group_read_iops_fn)
                         blkiop->ops.blkio_update_group_read_iops_fn(blkg->q,
                                                                 blkg, iops);
 
-                if (fileid == BLKIO_THROTL_write_iops_device
-                    && blkiop->ops.blkio_update_group_write_iops_fn)
+                if (rw == WRITE && blkiop->ops.blkio_update_group_write_iops_fn)
                         blkiop->ops.blkio_update_group_write_iops_fn(blkg->q,
                                                                 blkg,iops);
         }
@@ -975,19 +964,40 @@ static int blkcg_print_avg_queue_size(struct cgroup *cgrp, struct cftype *cft,
 }
 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
 
-static int blkio_policy_parse_and_set(char *buf, enum blkio_policy_id plid,
-                                      int fileid, struct blkio_cgroup *blkcg)
+struct blkg_conf_ctx {
+        struct gendisk          *disk;
+        struct blkio_group      *blkg;
+        u64                     v;
+};
+
+/**
+ * blkg_conf_prep - parse and prepare for per-blkg config update
+ * @blkcg: target block cgroup
+ * @input: input string
+ * @ctx: blkg_conf_ctx to be filled
+ *
+ * Parse per-blkg config update from @input and initialize @ctx with the
+ * result.  @ctx->blkg points to the blkg to be updated and @ctx->v the new
+ * value.  This function returns with RCU read locked and must be paired
+ * with blkg_conf_finish().
+ */
+static int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
+                          struct blkg_conf_ctx *ctx)
+        __acquires(rcu)
 {
-        struct gendisk *disk = NULL;
-        struct blkio_group *blkg = NULL;
-        struct blkg_policy_data *pd;
-        char *s[4], *p, *major_s = NULL, *minor_s = NULL;
+        struct gendisk *disk;
+        struct blkio_group *blkg;
+        char *buf, *s[4], *p, *major_s, *minor_s;
         unsigned long major, minor;
         int i = 0, ret = -EINVAL;
         int part;
         dev_t dev;
         u64 temp;
 
+        buf = kstrdup(input, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+
         memset(s, 0, sizeof(s));
 
         while ((p = strsep(&buf, " ")) != NULL) {
@@ -1037,82 +1047,42 @@ static int blkio_policy_parse_and_set(char *buf, enum blkio_policy_id plid,
 
         if (IS_ERR(blkg)) {
                 ret = PTR_ERR(blkg);
-                goto out_unlock;
-        }
-
-        pd = blkg->pd[plid];
-
-        switch (plid) {
-        case BLKIO_POLICY_PROP:
-                if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
-                     temp > BLKIO_WEIGHT_MAX)
-                        goto out_unlock;
-
-                pd->conf.weight = temp;
-                blkio_update_group_weight(blkg, plid, temp ?: blkcg->weight);
-                break;
-        case BLKIO_POLICY_THROTL:
-                switch(fileid) {
-                case BLKIO_THROTL_read_bps_device:
-                        pd->conf.bps[READ] = temp;
-                        blkio_update_group_bps(blkg, plid, temp ?: -1, fileid);
-                        break;
-                case BLKIO_THROTL_write_bps_device:
-                        pd->conf.bps[WRITE] = temp;
-                        blkio_update_group_bps(blkg, plid, temp ?: -1, fileid);
-                        break;
-                case BLKIO_THROTL_read_iops_device:
-                        if (temp > THROTL_IOPS_MAX)
-                                goto out_unlock;
-                        pd->conf.iops[READ] = temp;
-                        blkio_update_group_iops(blkg, plid, temp ?: -1, fileid);
-                        break;
-                case BLKIO_THROTL_write_iops_device:
-                        if (temp > THROTL_IOPS_MAX)
-                                goto out_unlock;
-                        pd->conf.iops[WRITE] = temp;
-                        blkio_update_group_iops(blkg, plid, temp ?: -1, fileid);
-                        break;
+                rcu_read_unlock();
+                put_disk(disk);
+                /*
+                 * If queue was bypassing, we should retry.  Do so after a
+                 * short msleep().  It isn't strictly necessary but queue
+                 * can be bypassing for some time and it's always nice to
+                 * avoid busy looping.
+                 */
+                if (ret == -EBUSY) {
+                        msleep(10);
+                        ret = restart_syscall();
                 }
-                break;
-        default:
-                BUG();
+                goto out;
         }
+
+        ctx->disk = disk;
+        ctx->blkg = blkg;
+        ctx->v = temp;
         ret = 0;
-out_unlock:
-        rcu_read_unlock();
 out:
-        put_disk(disk);
-
-        /*
-         * If queue was bypassing, we should retry.  Do so after a short
-         * msleep().  It isn't strictly necessary but queue can be
-         * bypassing for some time and it's always nice to avoid busy
-         * looping.
-         */
-        if (ret == -EBUSY) {
-                msleep(10);
-                return restart_syscall();
-        }
+        kfree(buf);
         return ret;
 }
 
-static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
-                                       const char *buffer)
+/**
+ * blkg_conf_finish - finish up per-blkg config update
+ * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
+ *
+ * Finish up after per-blkg config update.  This function must be paired
+ * with blkg_conf_prep().
+ */
+static void blkg_conf_finish(struct blkg_conf_ctx *ctx)
+        __releases(rcu)
 {
-        int ret = 0;
-        char *buf;
-        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
-        enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
-        int fileid = BLKIOFILE_ATTR(cft->private);
-
-        buf = kstrdup(buffer, GFP_KERNEL);
-        if (!buf)
-                return -ENOMEM;
-
-        ret = blkio_policy_parse_and_set(buf, plid, fileid, blkcg);
-        kfree(buf);
-        return ret;
+        rcu_read_unlock();
+        put_disk(ctx->disk);
 }
 
 /* for propio conf */
@@ -1140,6 +1110,32 @@ static int blkcg_print_weight(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
+static int blkcg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
+                                   const char *buf)
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
+        struct blkg_policy_data *pd;
+        struct blkg_conf_ctx ctx;
+        int ret;
+
+        ret = blkg_conf_prep(blkcg, buf, &ctx);
+        if (ret)
+                return ret;
+
+        ret = -EINVAL;
+        pd = ctx.blkg->pd[BLKIO_POLICY_PROP];
+        if (pd && (!ctx.v || (ctx.v >= BLKIO_WEIGHT_MIN &&
+                              ctx.v <= BLKIO_WEIGHT_MAX))) {
+                pd->conf.weight = ctx.v;
+                blkio_update_group_weight(ctx.blkg, BLKIO_POLICY_PROP,
+                                          ctx.v ?: blkcg->weight);
+                ret = 0;
+        }
+
+        blkg_conf_finish(&ctx);
+        return ret;
+}
+
 static int blkcg_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
 {
         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
@@ -1181,39 +1177,67 @@ static u64 blkg_prfill_conf_u64(struct seq_file *sf,
 static int blkcg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
                                 struct seq_file *sf)
 {
-        int off;
-
-        switch (BLKIOFILE_ATTR(cft->private)) {
-        case BLKIO_THROTL_read_bps_device:
-                off = offsetof(struct blkio_group_conf, bps[READ]);
-                break;
-        case BLKIO_THROTL_write_bps_device:
-                off = offsetof(struct blkio_group_conf, bps[WRITE]);
-                break;
-        case BLKIO_THROTL_read_iops_device:
-                off = offsetof(struct blkio_group_conf, iops[READ]);
-                break;
-        case BLKIO_THROTL_write_iops_device:
-                off = offsetof(struct blkio_group_conf, iops[WRITE]);
-                break;
-        default:
-                return -EINVAL;
-        }
-
         blkcg_print_blkgs(sf, cgroup_to_blkio_cgroup(cgrp),
                           blkg_prfill_conf_u64, BLKIO_POLICY_THROTL,
-                          off, false);
+                          cft->private, false);
         return 0;
 }
+
+static int blkcg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft,
+                              const char *buf, int rw,
+                              void (*update)(struct blkio_group *, int, u64, int))
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
+        struct blkg_policy_data *pd;
+        struct blkg_conf_ctx ctx;
+        int ret;
+
+        ret = blkg_conf_prep(blkcg, buf, &ctx);
+        if (ret)
+                return ret;
+
+        ret = -EINVAL;
+        pd = ctx.blkg->pd[BLKIO_POLICY_THROTL];
+        if (pd) {
+                *(u64 *)((void *)&pd->conf + cft->private) = ctx.v;
+                update(ctx.blkg, BLKIO_POLICY_THROTL, ctx.v ?: -1, rw);
+                ret = 0;
+        }
+
+        blkg_conf_finish(&ctx);
+        return ret;
+}
+
+static int blkcg_set_conf_bps_r(struct cgroup *cgrp, struct cftype *cft,
+                                const char *buf)
+{
+        return blkcg_set_conf_u64(cgrp, cft, buf, READ, blkio_update_group_bps);
+}
+
+static int blkcg_set_conf_bps_w(struct cgroup *cgrp, struct cftype *cft,
+                                const char *buf)
+{
+        return blkcg_set_conf_u64(cgrp, cft, buf, WRITE, blkio_update_group_bps);
+}
+
+static int blkcg_set_conf_iops_r(struct cgroup *cgrp, struct cftype *cft,
+                                 const char *buf)
+{
+        return blkcg_set_conf_u64(cgrp, cft, buf, READ, blkio_update_group_iops);
+}
+
+static int blkcg_set_conf_iops_w(struct cgroup *cgrp, struct cftype *cft,
+                                 const char *buf)
+{
+        return blkcg_set_conf_u64(cgrp, cft, buf, WRITE, blkio_update_group_iops);
+}
 #endif
 
 struct cftype blkio_files[] = {
         {
                 .name = "weight_device",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_weight_device),
                 .read_seq_string = blkcg_print_weight_device,
-                .write_string = blkiocg_file_write,
+                .write_string = blkcg_set_weight_device,
                 .max_write_len = 256,
         },
         {
@@ -1276,37 +1300,33 @@ struct cftype blkio_files[] = {
 #ifdef CONFIG_BLK_DEV_THROTTLING
         {
                 .name = "throttle.read_bps_device",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_read_bps_device),
+                .private = offsetof(struct blkio_group_conf, bps[READ]),
                 .read_seq_string = blkcg_print_conf_u64,
-                .write_string = blkiocg_file_write,
+                .write_string = blkcg_set_conf_bps_r,
                 .max_write_len = 256,
         },
 
         {
                 .name = "throttle.write_bps_device",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_write_bps_device),
+                .private = offsetof(struct blkio_group_conf, bps[WRITE]),
                 .read_seq_string = blkcg_print_conf_u64,
-                .write_string = blkiocg_file_write,
+                .write_string = blkcg_set_conf_bps_w,
                 .max_write_len = 256,
         },
 
         {
                 .name = "throttle.read_iops_device",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_read_iops_device),
+                .private = offsetof(struct blkio_group_conf, iops[READ]),
                 .read_seq_string = blkcg_print_conf_u64,
-                .write_string = blkiocg_file_write,
+                .write_string = blkcg_set_conf_iops_r,
                 .max_write_len = 256,
         },
 
         {
                 .name = "throttle.write_iops_device",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_write_iops_device),
+                .private = offsetof(struct blkio_group_conf, iops[WRITE]),
                 .read_seq_string = blkcg_print_conf_u64,
-                .write_string = blkiocg_file_write,
+                .write_string = blkcg_set_conf_iops_w,
                 .max_write_len = 256,
         },
         {
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index b67eefa706c3..108ffbf0d184 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -50,19 +50,6 @@ enum blkg_state_flags {
         BLKG_empty,
 };
 
-/* cgroup files owned by proportional weight policy */
-enum blkcg_file_name_prop {
-        BLKIO_PROP_weight_device,
-};
-
-/* cgroup files owned by throttle policy */
-enum blkcg_file_name_throtl {
-        BLKIO_THROTL_read_bps_device,
-        BLKIO_THROTL_write_bps_device,
-        BLKIO_THROTL_read_iops_device,
-        BLKIO_THROTL_write_iops_device,
-};
-
 struct blkio_cgroup {
         struct cgroup_subsys_state css;
         unsigned int weight;