[PATCH v5 17/17] cifs: invalidate cached_dirents if population aborted

[nspmangalore@gmail.com]

From: Shyam Prasad N <sprasad@microsoft.com>

In order to make sure that parallel readdirs do not populate
the cfid->cached_dirents, only the first readdir is given
"ownership" of populating cached_dirents. However, if the
next readdir on the same FD never arrives, we will always
miss the dirent cache.

This change introduces a 10-second timeout which will be used
by laundromat thread to check if the cached_dirents can be
invalidated. Ten seconds is a long enough interval between
successive readdir calls.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
---
 fs/smb/client/cached_dir.c | 65 ++++++++++++++++++++++++++++++++++----
 fs/smb/client/cached_dir.h |  1 +
 2 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index 3cf4cfa23c377..fa1ebc7132475 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -23,12 +23,18 @@ static void cfids_laundromat_worker(struct work_struct *work);
 
 #define CACHED_DIRENT_HASH_BITS	7
 #define CACHED_DIR_DENTRY_HT_BITS	8
+#define CACHED_DIR_POPULATE_TIMEOUT	10
 
 struct cached_dir_dentry {
 	struct list_head entry;
 	struct dentry *dentry;
 };
 
+struct cached_dir_invalidate_entry {
+	struct list_head entry;
+	struct cached_fid *cfid;
+};
+
 /* Generic helpers */
 bool cached_dir_is_valid(struct cached_fid *cfid)
 {
@@ -496,6 +502,7 @@ static void fail_cached_dir_locked(struct cached_dirents *cde)
 	 * can claim this slot and repopulate the cache.
 	 */
 	cde->file = NULL;
+	cde->last_populate_time = 0;
 }
 
 /* insert cached_dirent into lookup hashtable */
@@ -799,6 +806,7 @@ bool emit_cached_dir_if_valid(struct cached_fid *cfid,
 		cfid->dirents.file = file;
 		cfid->dirents.dir_inode = file_inode(file);
 		cfid->dirents.pos = 2;
+		cfid->dirents.last_populate_time = jiffies;
 		cached_dir_reset_insert_cursor_locked(&cfid->dirents);
 		/*
 		 * A previous population attempt may have failed and left
@@ -851,6 +859,28 @@ static void finished_cached_dirents_count(struct cached_dirents *cde,
 		cached_mapping->folio_is_eof = 1;
 
 	cde->is_valid = 1;
+	cde->last_populate_time = 0;
+}
+
+static void maybe_invalidate_stale_cached_dirents(struct cached_fid *cfid)
+{
+	struct cached_dirents *cde = &cfid->dirents;
+
+	mutex_lock(&cde->de_mutex);
+	if (cde->last_populate_time && !cde->is_valid && !cde->is_failed &&
+	    cde->file &&
+	    time_after(jiffies,
+		       cde->last_populate_time + HZ * CACHED_DIR_POPULATE_TIMEOUT))
+		fail_cached_dir_locked(cde);
+	mutex_unlock(&cde->de_mutex);
+}
+
+static unsigned long cached_dir_laundromat_interval_seconds(void)
+{
+	if (!dir_cache_timeout)
+		return CACHED_DIR_POPULATE_TIMEOUT;
+
+	return min_t(unsigned int, dir_cache_timeout, CACHED_DIR_POPULATE_TIMEOUT);
 }
 
 /* update the cached_dirent for a given name in list */
@@ -992,6 +1022,8 @@ bool add_to_cached_dir(struct cached_fid *cfid,
 	old_bytes = cfid->dirents.bytes_used;
 	added = add_cached_dirent(&cfid->dirents, ctx, name, namelen,
 				  fattr, file);
+	if (added)
+		cfid->dirents.last_populate_time = jiffies;
 	new_entries = cfid->dirents.entries_count;
 	new_bytes = cfid->dirents.bytes_used;
 	mutex_unlock(&cfid->dirents.de_mutex);
@@ -2098,7 +2130,9 @@ static void cfids_laundromat_worker(struct work_struct *work)
 {
 	struct cached_fids *cfids;
 	struct cached_fid *cfid, *q;
+	struct cached_dir_invalidate_entry *inv, *inv_q;
 	LIST_HEAD(entry);
+	LIST_HEAD(invalidate_list);
 
 	cfids = container_of(work, struct cached_fids, laundromat_work.work);
 
@@ -2108,6 +2142,9 @@ static void cfids_laundromat_worker(struct work_struct *work)
 
 	for (struct rb_node *rb_node = rb_first(&cfids->entries), *next_node;
 	     rb_node; rb_node = next_node) {
+		struct cached_dir_invalidate_entry *inv_ent;
+		unsigned long last_populate_time;
+
 		next_node = rb_next(rb_node);
 		cfid = rb_entry(rb_node, struct cached_fid, node);
 		spin_lock(&cfid->cfid_lock);
@@ -2131,11 +2168,29 @@ static void cfids_laundromat_worker(struct work_struct *work)
 				kref_get(&cfid->refcount);
 			}
 		} else {
+			last_populate_time = READ_ONCE(cfid->dirents.last_populate_time);
+			if (last_populate_time &&
+			    time_after(jiffies,
+				       last_populate_time + HZ * CACHED_DIR_POPULATE_TIMEOUT)) {
+				inv_ent = kmalloc_obj(*inv_ent, GFP_ATOMIC);
+				if (inv_ent) {
+					kref_get(&cfid->refcount);
+					inv_ent->cfid = cfid;
+					list_add_tail(&inv_ent->entry, &invalidate_list);
+				}
+			}
 			spin_unlock(&cfid->cfid_lock);
 		}
 	}
 	spin_unlock(&cfids->cfid_list_lock);
 
+	list_for_each_entry_safe(inv, inv_q, &invalidate_list, entry) {
+		list_del(&inv->entry);
+		maybe_invalidate_stale_cached_dirents(inv->cfid);
+		close_cached_dir(inv->cfid);
+		kfree(inv);
+	}
+
 	list_for_each_entry_safe(cfid, q, &entry, dying_entry) {
 		list_del(&cfid->dying_entry);
 
@@ -2156,9 +2211,8 @@ static void cfids_laundromat_worker(struct work_struct *work)
 			 */
 			close_cached_dir(cfid);
 	}
-	if (dir_cache_timeout)
-		queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
-				   dir_cache_timeout * HZ);
+	queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
+			   cached_dir_laundromat_interval_seconds() * HZ);
 }
 
 struct cached_fids *init_cached_dirs(void)
@@ -2179,9 +2233,8 @@ struct cached_fids *init_cached_dirs(void)
 	INIT_LIST_HEAD(&cfids->dying);
 
 	INIT_DELAYED_WORK(&cfids->laundromat_work, cfids_laundromat_worker);
-	if (dir_cache_timeout)
-		queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
-				   dir_cache_timeout * HZ);
+	queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
+			   cached_dir_laundromat_interval_seconds() * HZ);
 
 	atomic_long_set(&cfids->total_dirents_entries, 0);
 	atomic64_set(&cfids->total_dirents_bytes, 0);
diff --git a/fs/smb/client/cached_dir.h b/fs/smb/client/cached_dir.h
index 4091fa7867618..b41d157ec2f08 100644
--- a/fs/smb/client/cached_dir.h
+++ b/fs/smb/client/cached_dir.h
@@ -120,6 +120,7 @@ struct cached_dirents {
 	struct inode *dir_inode;
 	struct mutex de_mutex;
 	loff_t pos;		 /* Expected ctx->pos */
+	unsigned long last_populate_time; /* jiffies of last successful populate progress */
 	struct folio_queue *folioq;
 	struct list_head entry_list;
 	unsigned int entry_list_count;
-- 
2.43.0