The use of Seq_file

/*

Initialize Code

*/

Entry = Create_proc_entry (Cache_file_path, 0, NULL);

if (entry) {

Entry->proc_fops = &flashcache_cache_operations;

Entry->data = DMC;

}

Kfree (s);

/*

Destroying function code

*/

Remove_proc_entry (Cache_file_path,null);

Kfree (s);

Simple Way to Single_open

static int

Flashcache_version_show (struct seq_file*seq, void *v)

{

seq_printf (seq, "flashcacheversion:%s\n", flashcache_sw_version);

#ifdef Commit_rev

seq_printf (seq, "Git commit:%s\n", commit_rev);

#endif

return 0;

}

static int

Flashcache_version_open (struct inode*inode, struct file *file)

{

Return Single_open (File,&flashcache_version_show, PDE (inode)->data);

}

static struct file_operationsflashcache_version_operations = {

. open = Flashcache_version_open,

. Read = Seq_read,

. Llseek = Seq_lseek,

. Release = Single_release,

};

Advantages and Disadvantages

The advantage of this method is simple, but after testing in a show function of the seq_printf will first output to the Seq_file buff, when the output data is too large, there is a buffer overflow error, resulting in cannotallocate memory error.

The complex way Seq_open

/*

Returns null if the current iteration position exceeds the bounds of the list

*/

Static Void*flashcache_cache_start (struct Seq_file *seq, loff_t *pos)

{

struct Cache_c *DMC = seq->private;

if (*pos >= (dmc->num_sets *dmc->assoc)) {

return NULL;

}

Return &dmc->cache[*pos];

}

/*

If the current iteration position exceeds the bounds of the list, NULL is returned.

*/

Static Void*flashcache_cache_next (struct seq_file *seq, void *v, loff_t *pos)

{

struct Cache_c *DMC = seq->private;

(*pos) + +;

if (*pos >= (dmc->num_sets *dmc->assoc)) {

return NULL;

}

Return &dmc->cache[*pos];

}

Static voidflashcache_cache_stop (struct seq_file *seq, void *v)

{

}

/*

If the function outputs less data, return to the next function to continue the iteration. When the show function produces a certain amount of output, the iteration enters into the start function. When one of the next or start functions returns NULL, the iteration stops

*/

static int flashcache_cache_show (Structseq_file *seq, void *v)

{

struct Cacheblock *cache = (Structcacheblock *) v;

if (Cache->cache_state & VALID) {

seq_printf (seq, "%llu", (u_int64_t) CACHE->DBN);

}

return 0;

}

static struct Seq_operationsflashcache_cache_seq_ops = {

. Start = Flashcache_cache_start,

. Next = Flashcache_cache_next,

. Stop = Flashcache_cache_stop,

. Show = Flashcache_cache_show,

};

/*

Here set Seq_file's private,private as private member passed in the iteration

*/

static int

Flashcache_cache_open (struct inode*inode, struct file *file)

{

struct Seq_file *seq;

int ret;

ret = Seq_open (file,&flashcache_cache_seq_ops);

if (ret) {

return ret;

}

Seq = (struct seq_file*) file->private_data;

Seq->private = PDE (inode)->data;

return 0;

}

static struct file_operationsflashcache_cache_operations = {

. open = Flashcache_cache_open,

. Read = Seq_read,

. Llseek = Seq_lseek,

. Release = Seq_release,

};

Reference documents