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    Subject[tip:tracing/blktrace] blktrace: print human-readable act_mask
    Commit-ID:  093419971e03362a00f499960557c119982ea09f
    Gitweb: http://git.kernel.org/tip/093419971e03362a00f499960557c119982ea09f
    Author: Li Zefan <lizf@cn.fujitsu.com>
    AuthorDate: Tue, 24 Mar 2009 17:43:30 +0800
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Tue, 24 Mar 2009 13:09:00 +0100

    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>


    ---
    kernel/trace/blktrace.c | 103 +++++++++++++++++++++++++++++-----------------
    1 files changed, 65 insertions(+), 38 deletions(-)

    diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
    index f69f8bd..6fb274f 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));

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