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SubjectRe: [PATCH] blk queue io tracing support
Hi Jens,

On Wed, Aug 24, 2005 at 11:28:39AM +0200, Jens Axboe wrote:
> Ok, updated version.

One thing I found a bit awkward was the way its putting all inodes
in the root of the relayfs namespace, with the cpuid tacked on the
end of the bdevname - I was a bit confused at first when a trace of
sdd on my 4P box spontaneously created files for "partitions" sdd0,
sdd1, sdd2, and sdd3 ;).

I suppose if many more users of relayfs spring into existance, this
is going to get quite ugly. Below is a patch that aligns the names
to the conventions used in sysfs; so, for example, when running two
traces simultaneously on /dev/sdd and /dev/sdb, instead of this:

# find /relay
/relay
/relay/sdd3
/relay/sdd2
/relay/sdd1
/relay/sdd0
/relay/sdb3
/relay/sdb2
/relay/sdb1
/relay/sdb0

it now uses this...

# find /relay
/relay
/relay/block
/relay/block/sdd
/relay/block/sdd/trace3
/relay/block/sdd/trace2
/relay/block/sdd/trace1
/relay/block/sdd/trace0
/relay/block/sdb
/relay/block/sdb/trace3
/relay/block/sdb/trace2
/relay/block/sdb/trace1
/relay/block/sdb/trace0

and does the correct dynamic setup and teardown of the hierarchy
as the userspace tool starts and stops tracing. I had to modify
the relayfs rmdir code a bit to make this work properly, I'll
send a separate patch for that shortly.

> http://www.kernel.org/pub/linux/kernel/people/axboe/tools/blktrace.c
>
> has been updated as well, the protocol version was increased to
> accomodate the trace structure changes.

I have the associated userspace change for this, as well as several
other fixes and tweaks for your tool - if you could slap a copyright
and license notice onto that source (pretty please? :) I'll send 'em
right along.

cheers.

--
Nathan

Index: 2.6.x-xfs/drivers/block/blktrace.c
===================================================================
--- 2.6.x-xfs.orig/drivers/block/blktrace.c
+++ 2.6.x-xfs/drivers/block/blktrace.c
@@ -40,6 +40,50 @@ void __blk_add_trace(struct blk_trace *b
local_irq_restore(flags);
}

+static struct dentry * blk_tree_root;
+static DEFINE_SPINLOCK(blk_tree_lock);
+
+static inline void blk_remove_root(void)
+{
+ if (relayfs_remove_dir(blk_tree_root) != -ENOTEMPTY)
+ blk_tree_root = NULL;
+}
+
+static void blk_remove_tree(struct dentry *dir)
+{
+ spin_lock(&blk_tree_lock);
+ relayfs_remove_dir(dir);
+ blk_remove_root();
+ spin_unlock(&blk_tree_lock);
+}
+
+static struct dentry *blk_create_tree(const char *blk_name)
+{
+ struct dentry *dir;
+
+ spin_lock(&blk_tree_lock);
+ if (!blk_tree_root) {
+ blk_tree_root = relayfs_create_dir("block", NULL);
+ if (!blk_tree_root) {
+ spin_unlock(&blk_tree_lock);
+ return NULL;
+ }
+ }
+ dir = relayfs_create_dir(blk_name, blk_tree_root);
+ if (!dir)
+ blk_remove_root();
+ spin_unlock(&blk_tree_lock);
+
+ return dir;
+}
+
+void blk_cleanup_trace(struct blk_trace *bt)
+{
+ relay_close(bt->rchan);
+ blk_remove_tree(bt->dir);
+ kfree(bt);
+}
+
int blk_stop_trace(struct block_device *bdev)
{
request_queue_t *q = bdev_get_queue(bdev);
@@ -61,10 +105,8 @@ int blk_stop_trace(struct block_device *

up(&bdev->bd_sem);

- if (bt) {
- relay_close(bt->rchan);
- kfree(bt);
- }
+ if (bt)
+ blk_cleanup_trace(bt);

return ret;
}
@@ -74,6 +116,7 @@ int blk_start_trace(struct block_device
request_queue_t *q = bdev_get_queue(bdev);
struct blk_user_trace_setup buts;
struct blk_trace *bt = NULL;
+ struct dentry *dir = NULL;
char b[BDEVNAME_SIZE];
int ret;

@@ -101,11 +144,16 @@ int blk_start_trace(struct block_device
if (!bt)
goto err;

+ ret = -ENOENT;
+ dir = blk_create_tree(bdevname(bdev, b));
+ if (!dir)
+ goto err;
+
+ bt->dir = dir;
atomic_set(&bt->sequence, 0);

- bt->rchan = relay_open(bdevname(bdev, b), NULL, buts.buf_size,
- buts.buf_nr, NULL);
ret = -EIO;
+ bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, NULL);
if (!bt->rchan)
goto err;

@@ -122,6 +170,8 @@ int blk_start_trace(struct block_device

err:
up(&bdev->bd_sem);
+ if (dir)
+ blk_remove_tree(dir);
if (bt)
kfree(bt);
return ret;
Index: 2.6.x-xfs/include/linux/blktrace.h
===================================================================
--- 2.6.x-xfs.orig/include/linux/blktrace.h
+++ 2.6.x-xfs/include/linux/blktrace.h
@@ -71,6 +71,7 @@ struct blk_io_trace {
};

struct blk_trace {
+ struct dentry *dir;
struct rchan *rchan;
atomic_t sequence;
u16 act_mask;
@@ -89,6 +90,7 @@ struct blk_user_trace_setup {
#if defined(CONFIG_BLK_DEV_IO_TRACE)
extern int blk_start_trace(struct block_device *, char __user *);
extern int blk_stop_trace(struct block_device *);
+extern void blk_cleanup_trace(struct blk_trace *);
extern void __blk_add_trace(struct blk_trace *, sector_t, int, int, u32, int, int, char *);

static inline void blk_add_trace_rq(struct request_queue *q, struct request *rq,
@@ -137,6 +139,7 @@ static inline void blk_add_trace_generic
#else /* !CONFIG_BLK_DEV_IO_TRACE */
#define blk_start_trace(bdev, arg) (-EINVAL)
#define blk_stop_trace(bdev) (-EINVAL)
+#define blk_cleanup_trace(bt) do { } while (0)
#define blk_add_trace_rq(q, rq, what) do { } while (0)
#define blk_add_trace_bio(q, rq, what) do { } while (0)
#define blk_add_trace_generic(q, rq, rw, what) do { } while (0)
Index: 2.6.x-xfs/drivers/block/ll_rw_blk.c
===================================================================
--- 2.6.x-xfs.orig/drivers/block/ll_rw_blk.c
+++ 2.6.x-xfs/drivers/block/ll_rw_blk.c
@@ -1625,8 +1625,7 @@ void blk_cleanup_queue(request_queue_t *
__blk_queue_free_tags(q);

if (q->blk_trace) {
- relay_close(q->blk_trace->rchan);
- kfree(q->blk_trace);
+ blk_cleanup_trace(q->blk_trace);
q->blk_trace = NULL;
}

-
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