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Date: Fri, 21 Nov 2008 03:15:39 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: David Howells <dhowells@...hat.com>
Cc: trond.myklebust@....uio.no, viro@...IV.linux.org.uk,
nfsv4@...ux-nfs.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 11/45] FS-Cache: Add use of /proc and presentation of
statistics [ver #41]
On Thu, Nov 20, 2008 at 02:42:36PM +0000, David Howells wrote:
> Make FS-Cache create its /proc interface and present various statistical
> information through it. Also provide the functions for updating this
> information.
>
> These features are enabled by:
>
> CONFIG_FSCACHE_PROC
> CONFIG_FSCACHE_STATS
> CONFIG_FSCACHE_HISTOGRAM
I'd say, if one enabled PROC_FS and this fscache stuff, one should get files
in /proc. More, if one enables "gather statistics" (if it's performance-
or space- sensitive), one also gets fs/fscache/stats et al.
config option per proc file is way too much.
> The /proc directory for FS-Cache is also exported so that caching modules can
> add their own statistics there too.
No need, see below.
> The FS-Cache module is loadable at this point, and the statistics files can be
> examined by userspace:
>
> cat /proc/fs/fscache/stats
> cat /proc/fs/fscache/histogram
> --- /dev/null
> +++ b/fs/fscache/fsc-proc.c
> @@ -0,0 +1,370 @@
> +struct fscache_proc {
> + unsigned nlines;
> + const struct seq_operations *ops;
> +};
> +
> +struct proc_dir_entry *proc_fscache;
> +EXPORT_SYMBOL(proc_fscache);
Export isn't needed because other modules can just create by path their proc
files and it will work as expected:
pde = proc_create("fs/fscache/xxx",...)
> +#if defined(CONFIG_FSCACHE_STATS) || defined(CONFIG_FSCACHE_HISTOGRAM)
> +static int fscache_proc_open(struct inode *inode, struct file *file);
> +static void *fscache_proc_start(struct seq_file *m, loff_t *pos);
> +static void fscache_proc_stop(struct seq_file *m, void *v);
> +static void *fscache_proc_next(struct seq_file *m, void *v, loff_t *pos);
> +
> +static const struct file_operations fscache_proc_fops = {
> + .open = fscache_proc_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = seq_release,
> +};
> +#endif
> +
> +#ifdef CONFIG_FSCACHE_STATS
> +static int fscache_stats_show(struct seq_file *m, void *v);
> +
> +static const struct seq_operations fscache_stats_ops = {
> + .start = fscache_proc_start,
> + .stop = fscache_proc_stop,
> + .next = fscache_proc_next,
> + .show = fscache_stats_show,
> +};
> +
> +static const struct fscache_proc fscache_stats = {
> + .nlines = 17,
> + .ops = &fscache_stats_ops,
> +};
> +#endif
> +
> +#ifdef CONFIG_FSCACHE_HISTOGRAM
> +static int fscache_histogram_show(struct seq_file *m, void *v);
> +
> +static const struct seq_operations fscache_histogram_ops = {
> + .start = fscache_proc_start,
> + .stop = fscache_proc_stop,
> + .next = fscache_proc_next,
> + .show = fscache_histogram_show,
> +};
> +
> +static const struct fscache_proc fscache_histogram = {
> + .nlines = HZ + 1,
> + .ops = &fscache_histogram_ops,
> +};
> +#endif
> +
> +#define FSC_DESC(SELECT, N) ((void *) (unsigned long) (((SELECT) << 16) | (N)))
> +
> +/*
> + * initialise the /proc/fs/fscache/ directory
> + */
> +int __init fscache_proc_init(void)
> +{
> +#if defined(CONFIG_FSCACHE_STATS) || defined(CONFIG_FSCACHE_HISTOGRAM)
> + struct proc_dir_entry *p;
> +#endif
> +
> + _enter("");
> +
> + proc_fscache = proc_mkdir("fs/fscache", NULL);
> + if (!proc_fscache)
> + goto error_dir;
> + proc_fscache->owner = THIS_MODULE;
->owner settings is not needed nowadays.
> +#ifdef CONFIG_FSCACHE_STATS
> + p = create_proc_entry("stats", 0, proc_fscache);
> + if (!p)
> + goto error_stats;
> + p->proc_fops = &fscache_proc_fops;
> + p->owner = THIS_MODULE;
> + p->data = (void *) &fscache_stats;
> +#endif
a) set .owner in ->proc_fops instead
b) use (in your case) proc_create_data()
> +
> +#ifdef CONFIG_FSCACHE_HISTOGRAM
> + p = create_proc_entry("histogram", 0, proc_fscache);
> + if (!p)
> + goto error_histogram;
> + p->proc_fops = &fscache_proc_fops;
> + p->owner = THIS_MODULE;
> + p->data = (void *) &fscache_histogram;
> +#endif
ditto
> +#if defined(CONFIG_FSCACHE_STATS) || defined(CONFIG_FSCACHE_HISTOGRAM)
> +/*
> + * open "/proc/fs/fscache/XXX" which provide statistics summaries
> + */
> +static int fscache_proc_open(struct inode *inode, struct file *file)
> +{
> + const struct fscache_proc *proc = PDE(inode)->data;
> + struct seq_file *m;
> + int ret;
> +
> + ret = seq_open(file, proc->ops);
> + if (ret == 0) {
> + m = file->private_data;
> + m->private = (void *) proc;
> + }
> + return ret;
> +}
> +
> +/*
> + * set up the iterator to start reading from the first line
> + */
> +static void *fscache_proc_start(struct seq_file *m, loff_t *_pos)
> +{
> + if (*_pos == 0)
> + *_pos = 1;
> + return (void *)(unsigned long) *_pos;
> +}
> +
> +/*
> + * move to the next line
> + */
> +static void *fscache_proc_next(struct seq_file *m, void *v, loff_t *pos)
> +{
> + const struct fscache_proc *proc = m->private;
> +
> + (*pos)++;
> + return *pos > proc->nlines ? NULL : (void *)(unsigned long) *pos;
> +}
> +
> +/*
> + * clean up after reading
> + */
> +static void fscache_proc_stop(struct seq_file *m, void *v)
> +{
> +}
> +#endif
> +
> +#ifdef CONFIG_FSCACHE_STATS
> +/*
> + * display the general statistics
> + */
> +static int fscache_stats_show(struct seq_file *m, void *v)
> +{
> + unsigned long line = (unsigned long) v;
> +
> + switch (line) {
> + case 1:
> + seq_puts(m, "FS-Cache statistics\n");
> + break;
> +
> + case 2:
> + seq_printf(m, "Cookies: idx=%u dat=%u spc=%u\n",
> + atomic_read(&fscache_n_cookie_index),
> + atomic_read(&fscache_n_cookie_data),
> + atomic_read(&fscache_n_cookie_special));
> + break;
This is overly complex for unclear need. Just set_printf() all these lines
and drop iterator business. Use single_open()! Ditto for histo stuff.
> + case 3:
> + case 4:
> + case 5:
> + case 6:
> + case 7:
> + case 8:
> + case 9:
> + case 10:
> + case 11:
> + case 12:
> + case 13:
> + case 14:
> + case 15:
> + case 16:
> + case 17:
> + case 18:
> + return 0;
> +}
> +
> +#endif /* end CONFIG_FSCACHE_STATS */
> +
> +#ifdef CONFIG_FSCACHE_HISTOGRAM
...
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