Messages in this thread | | | Date | Sun, 22 Jun 2008 22:29:53 +0300 | From | "Pekka Enberg" <> | Subject | Re: [PATCH 3/3] relay: Add buffer-only channels; useful for early logging. |
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On Sat, Jun 21, 2008 at 5:11 PM, Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> wrote: > Allows one to create and use a channel with no associated files. Files > can be initialized later. This is useful in scenarios such as logging > in early code, before VFS is up. Therefore, such channels can be > created and used as soon as kmem_cache_init() completed. > > This is needed by kmemtrace to do tracing in early kernel code. > > +static int relay_setup_buf_file(struct rchan *chan, > + struct rchan_buf *buf, > + unsigned int cpu) > +{ > + struct dentry *dentry; > + unsigned long flags; > + char *tmpname; > + > + tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); > + if (!tmpname) > + goto failed;
Why don't you return -ENOMEM here?
> + snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu); > + > + /* Create file in fs */ > + dentry = chan->cb->create_buf_file(tmpname, chan->parent, > + S_IRUSR, buf, > + &chan->is_global); > + > + kfree(tmpname); > + > + if (!dentry) > + goto failed;
And here?
> + spin_lock_irqsave(&buf->rw_lock, flags); > + buf->dentry = dentry; > + buf->dentry->d_inode->i_size = buf->early_bytes; > + spin_unlock_irqrestore(&buf->rw_lock, flags); > + > + return 0; > + > +failed: > + return 1;
The separate goto seems pointless. Why don't you use negative return values for error handling?
> +} > + > /* > * relay_open_buf - create a new relay channel buffer > * > @@ -415,48 +448,33 @@ EXPORT_SYMBOL_GPL(relay_reset); > static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu) > { > struct rchan_buf *buf = NULL; > - struct dentry *dentry; > - char *tmpname; > > if (chan->is_global) > return chan->buf[0]; > > - tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); > - if (!tmpname) > - goto end; > - snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu); > - > buf = relay_create_buf(chan); > if (!buf) > - goto free_name; > + return NULL; > > spin_lock_init(&buf->rw_lock); > > + if (chan->has_base_filename) > + if (relay_setup_buf_file(chan, buf, cpu)) > + goto free_buf; > + > buf->cpu = cpu; > __relay_reset(buf, 1); > > - /* Create file in fs */ > - dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR, > - buf, &chan->is_global); > - if (!dentry) > - goto free_buf; > - > - buf->dentry = dentry; > - > if(chan->is_global) { > chan->buf[0] = buf; > buf->cpu = 0; > } > > - goto free_name; > + return buf; > > free_buf: > relay_destroy_buf(buf); > - buf = NULL; > -free_name: > - kfree(tmpname); > -end: > - return buf; > + return NULL; > } > > /** > @@ -539,8 +557,8 @@ static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb, > > /** > * relay_open - create a new relay channel > - * @base_filename: base name of files to create > - * @parent: dentry of parent directory, %NULL for root directory > + * @base_filename: base name of files to create, %NULL for buffering only > + * @parent: dentry of parent directory, %NULL for root directory or buffer > * @subbuf_size: size of sub-buffers > * @n_subbufs: number of sub-buffers > * @cb: client callback functions > @@ -562,8 +580,6 @@ struct rchan *relay_open(const char *base_filename, > { > unsigned int i; > struct rchan *chan; > - if (!base_filename) > - return NULL; > > if (!(subbuf_size && n_subbufs)) > return NULL; > @@ -578,7 +594,10 @@ struct rchan *relay_open(const char *base_filename, > chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs); > chan->parent = parent; > chan->private_data = private_data; > - strlcpy(chan->base_filename, base_filename, NAME_MAX); > + if (base_filename) { > + chan->has_base_filename = 1; > + strlcpy(chan->base_filename, base_filename, NAME_MAX); > + } > setup_callbacks(chan, cb); > kref_init(&chan->kref); > > @@ -607,6 +626,62 @@ free_bufs: > EXPORT_SYMBOL_GPL(relay_open); > > /** > + * relay_late_setup_files - triggers file creation > + * @chan: channel to operate on > + * @base_filename: base name of files to create > + * @parent: dentry of parent directory, %NULL for root directory > + * > + * Returns 0 if successful, non-zero otherwise. > + * > + * Use to setup files for a previously buffer-only channel. > + * Useful to do early tracing in kernel, before VFS is up, for example. > + */ > +int relay_late_setup_files(struct rchan *chan, > + const char *base_filename, > + struct dentry *parent) > +{ > + unsigned int i; > + int err; > + struct rchan_buf *buf; > + > + if (!chan || !base_filename) > + return 1;
-EINVAL?
> + > + strlcpy(chan->base_filename, base_filename, NAME_MAX); > + > + mutex_lock(&relay_channels_mutex); > + if (unlikely(chan->has_base_filename)) > + goto out;
-EINVAL?
> + chan->has_base_filename = 1; > + chan->parent = parent; > + /* > + * The CPU hotplug notifier ran before us and created buffers with > + * no files associated. So it's safe to call relay_setup_buf_file() > + * on all currently online CPUs. > + */ > + for_each_online_cpu(i) { > + buf = chan->buf[i]; > + > + if (unlikely(!buf)) { > + printk(KERN_ERR "relay_late_setup_files: " > + "all CPUs should have buffers!\n"); > + goto out; > + } > + > + err = relay_setup_buf_file(chan, buf, i); > + if (unlikely(err)) > + goto out; > + } > + mutex_unlock(&relay_channels_mutex); > + > + return 0; > + > +out: > + mutex_unlock(&relay_channels_mutex); > + return 1;
You don't need two return statements (and coincidentally two unlocks) if you keep the return value in a local variable 'err'.
> +} > + > +/** > * relay_switch_subbuf - switch to a new sub-buffer > * @buf: channel buffer > * @length: size of current event > @@ -629,8 +704,13 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) > old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; > buf->padding[old_subbuf] = buf->prev_padding; > buf->subbufs_produced++; > - buf->dentry->d_inode->i_size += buf->chan->subbuf_size - > - buf->padding[old_subbuf]; > + if (buf->dentry) > + buf->dentry->d_inode->i_size += > + buf->chan->subbuf_size - > + buf->padding[old_subbuf]; > + else > + buf->early_bytes += buf->chan->subbuf_size - > + buf->padding[old_subbuf]; > smp_mb(); > if (waitqueue_active(&buf->read_wait)) > /* > @@ -1241,9 +1321,8 @@ EXPORT_SYMBOL_GPL(relay_file_operations); > > static __init int relay_init(void) > { > - > hotcpu_notifier(relay_hotcpu_callback, 0); > return 0; > } > > -module_init(relay_init); > +early_initcall(relay_init); > -- > 1.5.5.4 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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