9p: Performance improvements for build workloads

Documentation/filesystems/9p.rst

@@ -238,6 +238,11 @@ Options
   cachetag	cache tag to use the specified persistent cache.
 		cache tags for existing cache sessions can be listed at
 		/sys/fs/9p/caches. (applies only to cache=fscache)
+
+  negtimeout    the duration (in milliseconds) that negative dentries (paths
+                that do not actually exist) are retained in the cache. If
+                set to a negative value, those entries are kept indefinitely
+                until evicted by the buffer cache management system
   ============= ===============================================================
 
 Behavior

fs/9p/fid.c

@@ -20,7 +20,9 @@
 
 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
 {
-	hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
+	struct v9fs_dentry *v9fs_dentry = to_v9fs_dentry(dentry);
+
+	hlist_add_head(&fid->dlist, &v9fs_dentry->head);
 }
 
 
@@ -112,18 +114,17 @@ void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
 
 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
 {
+	struct v9fs_dentry *v9fs_dentry = to_v9fs_dentry(dentry);
 	struct p9_fid *fid, *ret;
 
 	p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
 		 dentry, dentry, from_kuid(&init_user_ns, uid),
 		 any);
 	ret = NULL;
 	/* we'll recheck under lock if there's anything to look in */
-	if (dentry->d_fsdata) {
-		struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
-
+	if (!hlist_empty(&v9fs_dentry->head)) {
 		spin_lock(&dentry->d_lock);
-		hlist_for_each_entry(fid, h, dlist) {
+		hlist_for_each_entry(fid, &v9fs_dentry->head, dlist) {
 			if (any || uid_eq(fid->uid, uid)) {
 				ret = fid;
 				p9_fid_get(ret);

fs/9p/v9fs.c

@@ -24,6 +24,9 @@
 #include "v9fs_vfs.h"
 #include "cache.h"
 
+/* cache=loose default negative dentry retention time is 24hours */
+#define CACHE_LOOSE_NDENTRY_TIMEOUT_DEFAULT (24 * 60 * 60 * 1000)
+
 static DEFINE_SPINLOCK(v9fs_sessionlist_lock);
 static LIST_HEAD(v9fs_sessionlist);
 struct kmem_cache *v9fs_inode_cache;
@@ -39,7 +42,7 @@ enum {
 	 * source if we rejected it as EINVAL */
 	Opt_source,
 	/* Options that take integer arguments */
-	Opt_debug, Opt_dfltuid, Opt_dfltgid, Opt_afid,
+	Opt_debug, Opt_dfltuid, Opt_dfltgid, Opt_afid, Opt_negtimeout,
 	/* String options */
 	Opt_uname, Opt_remotename, Opt_cache, Opt_cachetag,
 	/* Options that take no arguments */
@@ -93,6 +96,7 @@ const struct fs_parameter_spec v9fs_param_spec[] = {
 	fsparam_string	("access",	Opt_access),
 	fsparam_flag	("posixacl",	Opt_posixacl),
 	fsparam_u32	("locktimeout",	Opt_locktimeout),
+	fsparam_s32	("negtimeout",	Opt_negtimeout),
 
 	/* client options */
 	fsparam_u32	("msize",	Opt_msize),
@@ -159,6 +163,9 @@ int v9fs_show_options(struct seq_file *m, struct dentry *root)
 			   from_kgid_munged(&init_user_ns, v9ses->dfltgid));
 	if (v9ses->afid != ~0)
 		seq_printf(m, ",afid=%u", v9ses->afid);
+	if (v9ses->flags & V9FS_NDENTRY_TIMEOUT_SET)
+		seq_printf(m, ",negtimeout=%d",
+			   (int)v9ses->ndentry_timeout_ms);
 	if (strcmp(v9ses->uname, V9FS_DEFUSER) != 0)
 		seq_printf(m, ",uname=%s", v9ses->uname);
 	if (strcmp(v9ses->aname, V9FS_DEFANAME) != 0)
@@ -337,6 +344,16 @@ int v9fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		session_opts->session_lock_timeout = (long)result.uint_32 * HZ;
 		break;
 
+	case Opt_negtimeout:
+		session_opts->flags |= V9FS_NDENTRY_TIMEOUT_SET;
+		if (result.int_32 < 0) {
+			session_opts->ndentry_timeout_ms =
+				NDENTRY_TIMEOUT_NEVER;
+		} else {
+			session_opts->ndentry_timeout_ms = result.int_32;
+		}
+		break;
+
 	/* Options for client */
 	case Opt_msize:
 		if (result.uint_32 < 4096) {
@@ -422,6 +439,14 @@ static void v9fs_apply_options(struct v9fs_session_info *v9ses,
 	v9ses->cache = ctx->session_opts.cache;
 	v9ses->uid = ctx->session_opts.uid;
 	v9ses->session_lock_timeout = ctx->session_opts.session_lock_timeout;
+	v9ses->ndentry_timeout_ms = ctx->session_opts.ndentry_timeout_ms;
+
+	/* If negative dentry timeout has not been overriden set default for
+	 * cache=loose
+	 */
+	if (!(v9ses->flags & V9FS_NDENTRY_TIMEOUT_SET) &&
+	    (v9ses->cache & CACHE_LOOSE))
+		v9ses->ndentry_timeout_ms = CACHE_LOOSE_NDENTRY_TIMEOUT_DEFAULT;
 }
 
 /**

fs/9p/v9fs.h

@@ -24,6 +24,8 @@
  * @V9FS_ACCESS_ANY: use a single attach for all users
  * @V9FS_ACCESS_MASK: bit mask of different ACCESS options
  * @V9FS_POSIX_ACL: POSIX ACLs are enforced
+ * @V9FS_NDENTRY_TIMEOUT_SET: Has negative dentry timeout retention time been
+ *                            overriden by ndentrycache mount option
  *
  * Session flags reflect options selected by users at mount time
  */
@@ -34,16 +36,17 @@
 #define V9FS_ACL_MASK V9FS_POSIX_ACL
 
 enum p9_session_flags {
-	V9FS_PROTO_2000U    = 0x01,
-	V9FS_PROTO_2000L    = 0x02,
-	V9FS_ACCESS_SINGLE  = 0x04,
-	V9FS_ACCESS_USER    = 0x08,
-	V9FS_ACCESS_CLIENT  = 0x10,
-	V9FS_POSIX_ACL      = 0x20,
-	V9FS_NO_XATTR       = 0x40,
-	V9FS_IGNORE_QV      = 0x80, /* ignore qid.version for cache hints */
-	V9FS_DIRECT_IO      = 0x100,
-	V9FS_SYNC           = 0x200
+	V9FS_PROTO_2000U         = 0x01,
+	V9FS_PROTO_2000L         = 0x02,
+	V9FS_ACCESS_SINGLE       = 0x04,
+	V9FS_ACCESS_USER         = 0x08,
+	V9FS_ACCESS_CLIENT       = 0x10,
+	V9FS_POSIX_ACL           = 0x20,
+	V9FS_NO_XATTR            = 0x40,
+	V9FS_IGNORE_QV           = 0x80, /* ignore qid.version for cache hints */
+	V9FS_DIRECT_IO           = 0x100,
+	V9FS_SYNC                = 0x200,
+	V9FS_NDENTRY_TIMEOUT_SET = 0x400,
 };
 
 /**
@@ -91,6 +94,7 @@ enum p9_cache_bits {
  * @debug: debug level
  * @afid: authentication handle
  * @cache: cache mode of type &p9_cache_bits
+ * @ndentry_timeout: Negative dentry lookup cache retention time in ms
  * @cachetag: the tag of the cache associated with this session
  * @fscache: session cookie associated with FS-Cache
  * @uname: string user name to mount hierarchy as
@@ -101,6 +105,7 @@ enum p9_cache_bits {
  * @uid: if %V9FS_ACCESS_SINGLE, the numeric uid which mounted the hierarchy
  * @clnt: reference to 9P network client instantiated for this session
  * @slist: reference to list of registered 9p sessions
+ * @ndentry_timeout_ms: Negative dentry caching retention time
  *
  * This structure holds state for each session instance established during
  * a sys_mount() .
@@ -116,6 +121,7 @@ struct v9fs_session_info {
 	unsigned short debug;
 	unsigned int afid;
 	unsigned int cache;
+	unsigned int ndentry_timeout_ms;
 #ifdef CONFIG_9P_FSCACHE
 	char *cachetag;
 	struct fscache_volume *fscache;
@@ -133,6 +139,8 @@ struct v9fs_session_info {
 	long session_lock_timeout; /* retry interval for blocking locks */
 };
 
+#define NDENTRY_TIMEOUT_NEVER (-1U)
+
 /* cache_validity flags */
 #define V9FS_INO_INVALID_ATTR 0x01
 

fs/9p/v9fs_vfs.h

@@ -28,13 +28,28 @@
 /* flags for v9fs_stat2inode() & v9fs_stat2inode_dotl() */
 #define V9FS_STAT2INODE_KEEP_ISIZE 1
 
+/**
+ * struct v9fs_dentry - v9fs specific dentry data
+ * @head: List of fid associated with this dentry
+ * @expire_time: Lookup cache expiration time for negative dentries
+ * @rcu: used by kfree_rcu to schedule clean up job
+ */
+struct v9fs_dentry {
+	struct hlist_head head;
+	u64 expire_time;
+	struct rcu_head rcu;
+};
+#define to_v9fs_dentry(d) ((struct v9fs_dentry *)((d)->d_fsdata))
+
 extern struct file_system_type v9fs_fs_type;
 extern const struct address_space_operations v9fs_addr_operations;
 extern const struct file_operations v9fs_file_operations;
 extern const struct file_operations v9fs_file_operations_dotl;
 extern const struct file_operations v9fs_dir_operations;
 extern const struct file_operations v9fs_dir_operations_dotl;
 extern const struct dentry_operations v9fs_dentry_operations;
+extern void v9fs_ndentry_refresh_timeout(struct dentry *dentry);
+extern void v9fs_dentry_fid_remove(struct dentry *dentry);
 extern const struct dentry_operations v9fs_cached_dentry_operations;
 extern struct kmem_cache *v9fs_inode_cache;
 

fs/9p/vfs_addr.c

@@ -70,11 +70,31 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
 {
 	struct netfs_io_request *rreq = subreq->rreq;
 	struct p9_fid *fid = rreq->netfs_priv;
+	char *target;
 	unsigned long long pos = subreq->start + subreq->transferred;
-	int total, err;
-
-	total = p9_client_read(fid, pos, &subreq->io_iter, &err);
+	int total = 0, err, len, n;
+
+	if (S_ISLNK(rreq->inode->i_mode)) {
+		/* p9_client_readlink() must not be called for legacy protocols
+		 * 9p2000 or 9p2000.u.
+		 */
+		BUG_ON(!p9_is_proto_dotl(fid->clnt));
+		err = p9_client_readlink(fid, &target);
+		if (err != 0)
+			goto fill_subreq;
+		len = strnlen(target, PAGE_SIZE - 1);
+		n = copy_to_iter(target, len, &subreq->io_iter);
+		kfree(target);
+		if (n != len) {
+			err = -EFAULT;
+			goto fill_subreq;
+		}
+		total = i_size_read(rreq->inode);
+	} else {
+		total = p9_client_read(fid, pos, &subreq->io_iter, &err);
+	}
 
+fill_subreq:
 	/* if we just extended the file size, any portion not in
 	 * cache won't be on server and is zeroes */
 	if (subreq->rreq->origin != NETFS_UNBUFFERED_READ &&
@@ -99,6 +119,7 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
 static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
 	struct p9_fid *fid;
+	struct dentry *dentry;
 	bool writing = (rreq->origin == NETFS_READ_FOR_WRITE ||
 			rreq->origin == NETFS_WRITETHROUGH ||
 			rreq->origin == NETFS_UNBUFFERED_WRITE ||
@@ -115,6 +136,14 @@ static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
 		if (!fid)
 			goto no_fid;
 		p9_fid_get(fid);
+	} else if (S_ISLNK(rreq->inode->i_mode)) {
+		dentry = d_find_alias(rreq->inode);
+		if (!dentry)
+			goto no_fid;
+		fid = v9fs_fid_lookup(dentry);
+		dput(dentry);
+		if (IS_ERR(fid))
+			goto no_fid;
 	} else {
 		fid = v9fs_fid_find_inode(rreq->inode, writing, INVALID_UID, true);
 		if (!fid)