blktrace: print human-readable act_mask

Impact: new feature, allow symbolic values in /debug/tracing/act_mask

Print stringified act_mask instead of hex value:

 # cat act_mask
 read,write,barrier,sync,queue,requeue,issue,complete,fs,pc,ahead,meta,
 discard,drv_data
 # echo "meta,write" > act_mask
 # cat act_mask
 write,meta

Also:
 - make act_mask accept "ahead", "meta", "discard" and "drv_data"
 - use strsep() instead of strchr() to parse user input
 - return -EINVAL if a token is not found in the mask map
 - fix a bug that 'value' is unsigned, so it can < 0
 - propagate error value of blk_trace_mask2str() to userspace, but not
   always return -ENXIO.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <49C8AB42.1000802@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 65 insertions, 38 deletions

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index f69f8bd8bef9..6fb274f5f34e 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1316,53 +1316,77 @@ struct attribute_group blk_trace_attr_group = {
         .attrs = blk_trace_attrs,
 };
 
-static int blk_str2act_mask(const char *str)
+static const struct {
+        int mask;
+        const char *str;
+} mask_maps[] = {
+        { BLK_TC_READ,          "read"          },
+        { BLK_TC_WRITE,         "write"         },
+        { BLK_TC_BARRIER,       "barrier"       },
+        { BLK_TC_SYNC,          "sync"          },
+        { BLK_TC_QUEUE,         "queue"         },
+        { BLK_TC_REQUEUE,       "requeue"       },
+        { BLK_TC_ISSUE,         "issue"         },
+        { BLK_TC_COMPLETE,      "complete"      },
+        { BLK_TC_FS,            "fs"            },
+        { BLK_TC_PC,            "pc"            },
+        { BLK_TC_AHEAD,         "ahead"         },
+        { BLK_TC_META,          "meta"          },
+        { BLK_TC_DISCARD,       "discard"       },
+        { BLK_TC_DRV_DATA,      "drv_data"      },
+};
+
+static int blk_trace_str2mask(const char *str)
 {
+        int i;
         int mask = 0;
-        char *copy = kstrdup(str, GFP_KERNEL), *s;
+        char *s, *token;
 
-        if (copy == NULL)
+        s = kstrdup(str, GFP_KERNEL);
+        if (s == NULL)
                 return -ENOMEM;
-
-        s = strstrip(copy);
+        s = strstrip(s);
 
         while (1) {
-                char *sep = strchr(s, ',');
-
-                if (sep != NULL)
-                        *sep = '\0';
-
-                if (strcasecmp(s, "barrier") == 0)
-                        mask |= BLK_TC_BARRIER;
-                else if (strcasecmp(s, "complete") == 0)
-                        mask |= BLK_TC_COMPLETE;
-                else if (strcasecmp(s, "fs") == 0)
-                        mask |= BLK_TC_FS;
-                else if (strcasecmp(s, "issue") == 0)
-                        mask |= BLK_TC_ISSUE;
-                else if (strcasecmp(s, "pc") == 0)
-                        mask |= BLK_TC_PC;
-                else if (strcasecmp(s, "queue") == 0)
-                        mask |= BLK_TC_QUEUE;
-                else if (strcasecmp(s, "read") == 0)
-                        mask |= BLK_TC_READ;
-                else if (strcasecmp(s, "requeue") == 0)
-                        mask |= BLK_TC_REQUEUE;
-                else if (strcasecmp(s, "sync") == 0)
-                        mask |= BLK_TC_SYNC;
-                else if (strcasecmp(s, "write") == 0)
-                        mask |= BLK_TC_WRITE;
-
-                if (sep == NULL)
+                token = strsep(&s, ",");
+                if (token == NULL)
                         break;
 
-                s = sep + 1;
+                if (*token == '\0')
+                        continue;
+
+                for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
+                        if (strcasecmp(token, mask_maps[i].str) == 0) {
+                                mask |= mask_maps[i].mask;
+                                break;
+                        }
+                }
+                if (i == ARRAY_SIZE(mask_maps)) {
+                        mask = -EINVAL;
+                        break;
+                }
         }
-        kfree(copy);
+        kfree(s);
 
         return mask;
 }
 
+static ssize_t blk_trace_mask2str(char *buf, int mask)
+{
+        int i;
+        char *p = buf;
+
+        for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
+                if (mask & mask_maps[i].mask) {
+                        p += sprintf(p, "%s%s",
+                                    (p == buf) ? "" : ",", mask_maps[i].str);
+                }
+        }
+        *p++ = '\n';
+
+        return p - buf;
+}
+
 static struct request_queue *blk_trace_get_queue(struct block_device *bdev)
 {
         if (bdev->bd_disk == NULL)
@@ -1399,7 +1423,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
         if (q->blk_trace == NULL)
                 ret = sprintf(buf, "disabled\n");
         else if (attr == &dev_attr_act_mask)
-                ret = sprintf(buf, "%#x\n", q->blk_trace->act_mask);
+                ret = blk_trace_mask2str(buf, q->blk_trace->act_mask);
         else if (attr == &dev_attr_pid)
                 ret = sprintf(buf, "%u\n", q->blk_trace->pid);
         else if (attr == &dev_attr_start_lba)
@@ -1424,7 +1448,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
         struct request_queue *q;
         struct hd_struct *p;
         u64 value;
-        ssize_t ret = -ENXIO;
+        ssize_t ret = -EINVAL;
 
         if (count == 0)
                 goto out;
@@ -1432,13 +1456,16 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
         if (attr == &dev_attr_act_mask) {
                 if (sscanf(buf, "%llx", &value) != 1) {
                         /* Assume it is a list of trace category names */
-                        value = blk_str2act_mask(buf);
-                        if (value < 0)
+                        ret = blk_trace_str2mask(buf);
+                        if (ret < 0)
                                 goto out;
+                        value = ret;
                 }
         } else if (sscanf(buf, "%llu", &value) != 1)
                 goto out;
 
+        ret = -ENXIO;
+
         lock_kernel();
         p = dev_to_part(dev);
         bdev = bdget(part_devt(p));