smb: client: account smb directory cache usage and per-tcon totals

Add lightweight accounting for directory lease cache usage
to aid debugging and limiting cache size in future. Track
per-directory entry/byte counts and maintain per-tcon
aggregates. Also expose the totals in /proc/fs/cifs/open_dirs.

Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: bharathsm-ms

fs/smb/client/cached_dir.c

@@ -697,6 +697,21 @@ static void free_cached_dir(struct cached_fid *cfid)
 		kfree(dirent);
 	}
 
+	/* adjust tcon-level counters and reset per-dir accounting */
+	if (cfid->cfids) {
+		if (cfid->dirents.entries_count)
+			atomic_long_sub((long)cfid->dirents.entries_count,
+					&cfid->cfids->total_dirents_entries);
+		if (cfid->dirents.bytes_used) {
+			atomic64_sub((long long)cfid->dirents.bytes_used,
+					&cfid->cfids->total_dirents_bytes);
+			atomic64_sub((long long)cfid->dirents.bytes_used,
+					&cifs_dircache_bytes_used);
+		}
+	}
+	cfid->dirents.entries_count = 0;
+	cfid->dirents.bytes_used = 0;
+
 	kfree(cfid->path);
 	cfid->path = NULL;
 	kfree(cfid);
@@ -792,6 +807,9 @@ struct cached_fids *init_cached_dirs(void)
 	queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
 			   dir_cache_timeout * HZ);
 
+	atomic_long_set(&cfids->total_dirents_entries, 0);
+	atomic64_set(&cfids->total_dirents_bytes, 0);
+
 	return cfids;
 }
 

fs/smb/client/cached_dir.h

@@ -27,6 +27,9 @@ struct cached_dirents {
 	struct mutex de_mutex;
 	loff_t pos;		 /* Expected ctx->pos */
 	struct list_head entries;
+	/* accounting for cached entries in this directory */
+	unsigned long entries_count;
+	unsigned long bytes_used;
 };
 
 struct cached_fid {
@@ -62,8 +65,14 @@ struct cached_fids {
 	struct list_head dying;
 	struct work_struct invalidation_work;
 	struct delayed_work laundromat_work;
+	/* aggregate accounting for all cached dirents under this tcon */
+	atomic_long_t total_dirents_entries;
+	atomic64_t total_dirents_bytes;
 };
 
+/* Module-wide directory cache accounting (defined in cifsfs.c) */
+extern atomic64_t cifs_dircache_bytes_used; /* bytes across all mounts */
+
 extern struct cached_fids *init_cached_dirs(void);
 extern void free_cached_dirs(struct cached_fids *cfids);
 extern int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,

fs/smb/client/cifs_debug.c

@@ -331,7 +331,10 @@ static int cifs_debug_dirs_proc_show(struct seq_file *m, void *v)
 				if (!cfids)
 					continue;
 				spin_lock(&cfids->cfid_list_lock); /* check lock ordering */
-				seq_printf(m, "Num entries: %d\n", cfids->num_entries);
+				seq_printf(m, "Num entries: %d, cached_dirents: %lu entries, %llu bytes\n",
+						cfids->num_entries,
+						(unsigned long)atomic_long_read(&cfids->total_dirents_entries),
+						(unsigned long long)atomic64_read(&cfids->total_dirents_bytes));
 				list_for_each_entry(cfid, &cfids->entries, entry) {
 					seq_printf(m, "0x%x 0x%llx 0x%llx     %s",
 						tcon->tid,
@@ -342,6 +345,9 @@ static int cifs_debug_dirs_proc_show(struct seq_file *m, void *v)
 						seq_printf(m, "\tvalid file info");
 					if (cfid->dirents.is_valid)
 						seq_printf(m, ", valid dirents");
+					if (!list_empty(&cfid->dirents.entries))
+						seq_printf(m, ", dirents: %lu entries, %lu bytes",
+						cfid->dirents.entries_count, cfid->dirents.bytes_used);
 					seq_printf(m, "\n");
 				}
 				spin_unlock(&cfids->cfid_list_lock);

fs/smb/client/cifsfs.c

@@ -121,6 +121,8 @@ unsigned int dir_cache_timeout = 30;
 module_param(dir_cache_timeout, uint, 0644);
 MODULE_PARM_DESC(dir_cache_timeout, "Number of seconds to cache directory contents for which we have a lease. Default: 30 "
 				 "Range: 1 to 65000 seconds, 0 to disable caching dir contents");
+/* Module-wide total cached dirents (in bytes) across all tcons */
+atomic64_t cifs_dircache_bytes_used = ATOMIC64_INIT(0);
 
 /*
  * Write-only module parameter to drop all cached directory entries across

fs/smb/client/readdir.c

@@ -874,39 +874,42 @@ static void finished_cached_dirents_count(struct cached_dirents *cde,
 	cde->is_valid = 1;
 }
 
-static void add_cached_dirent(struct cached_dirents *cde,
-			      struct dir_context *ctx,
-			      const char *name, int namelen,
-			      struct cifs_fattr *fattr,
-				  struct file *file)
+static bool add_cached_dirent(struct cached_dirents *cde,
+			      struct dir_context *ctx, const char *name,
+			      int namelen, struct cifs_fattr *fattr,
+			      struct file *file)
 {
 	struct cached_dirent *de;
 
 	if (cde->file != file)
-		return;
+		return false;
 	if (cde->is_valid || cde->is_failed)
-		return;
+		return false;
 	if (ctx->pos != cde->pos) {
 		cde->is_failed = 1;
-		return;
+		return false;
 	}
 	de = kzalloc(sizeof(*de), GFP_ATOMIC);
 	if (de == NULL) {
 		cde->is_failed = 1;
-		return;
+		return false;
 	}
 	de->namelen = namelen;
 	de->name = kstrndup(name, namelen, GFP_ATOMIC);
 	if (de->name == NULL) {
 		kfree(de);
 		cde->is_failed = 1;
-		return;
+		return false;
 	}
 	de->pos = ctx->pos;
 
 	memcpy(&de->fattr, fattr, sizeof(struct cifs_fattr));
 
 	list_add_tail(&de->entry, &cde->entries);
+	/* update accounting */
+	cde->entries_count++;
+	cde->bytes_used += sizeof(*de) + (size_t)namelen + 1;
+	return true;
 }
 
 static bool cifs_dir_emit(struct dir_context *ctx,
@@ -915,18 +918,29 @@ static bool cifs_dir_emit(struct dir_context *ctx,
 			  struct cached_fid *cfid,
 			  struct file *file)
 {
-	bool rc;
+	size_t delta_bytes = 0;
+	bool rc, added = false;
 	ino_t ino = cifs_uniqueid_to_ino_t(fattr->cf_uniqueid);
 
 	rc = dir_emit(ctx, name, namelen, ino, fattr->cf_dtype);
 	if (!rc)
 		return rc;
 
 	if (cfid) {
+		/* Cost of this entry */
+		delta_bytes = sizeof(struct cached_dirent) + (size_t)namelen + 1;
+
 		mutex_lock(&cfid->dirents.de_mutex);
-		add_cached_dirent(&cfid->dirents, ctx, name, namelen,
-				  fattr, file);
+		added = add_cached_dirent(&cfid->dirents, ctx, name, namelen,
+					  fattr, file);
 		mutex_unlock(&cfid->dirents.de_mutex);
+
+		if (added) {
+			/* per-tcon then global for consistency with free path */
+			atomic64_add((long long)delta_bytes, &cfid->cfids->total_dirents_bytes);
+			atomic_long_inc(&cfid->cfids->total_dirents_entries);
+			atomic64_add((long long)delta_bytes, &cifs_dircache_bytes_used);
+		}
 	}
 
 	return rc;