gfapi: introduce glfs_readdir() and glfs_readdirplus() APIs

Change-Id: I6b233bf647585675f233898351bf593f251716cc
BUG: 839950
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/6201
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra Talur <rtalur@redhat.com>

api/src/glfs-fops.c

@@ -13,7 +13,15 @@
 #include "glfs-mem-types.h"
 #include "syncop.h"
 #include "glfs.h"
+#include <limits.h>
 
+#ifdef NAME_MAX
+#define GF_NAME_MAX NAME_MAX
+#else
+#define GF_NAME_MAX 255
+#endif
+
+#define READDIRBUF_SIZE (sizeof(struct dirent) + GF_NAME_MAX + 1)
 
 int
 glfs_loc_link (loc_t *loc, struct iatt *iatt)
@@ -1918,7 +1926,7 @@ gf_dirent_to_dirent (gf_dirent_t *gf_dirent, struct dirent *dirent)
 	dirent->d_namlen = strlen (gf_dirent->d_name);
 #endif
 
-	strncpy (dirent->d_name, gf_dirent->d_name, 256);
+	strncpy (dirent->d_name, gf_dirent->d_name, GF_NAME_MAX + 1);
 }
 
 
@@ -2012,16 +2020,56 @@ glfd_entry_next (struct glfs_fd *glfd, int plus)
 }
 
 
+static struct dirent *
+glfs_readdirbuf_get (struct glfs_fd *glfd)
+{
+        struct dirent *buf = NULL;
+
+        LOCK (&glfd->fd->lock);
+        {
+                buf = glfd->readdirbuf;
+                if (buf) {
+                        memset (buf, 0, READDIRBUF_SIZE);
+                        goto unlock;
+                }
+
+                buf = GF_CALLOC (1, READDIRBUF_SIZE, glfs_mt_readdirbuf_t);
+                if (!buf) {
+                        errno = ENOMEM;
+                        goto unlock;
+                }
+
+                glfd->readdirbuf = buf;
+        }
+unlock:
+        UNLOCK (&glfd->fd->lock);
+
+        return buf;
+}
+
+
 int
-glfs_readdirplus_r (struct glfs_fd *glfd, struct stat *stat, struct dirent *buf,
+glfs_readdirplus_r (struct glfs_fd *glfd, struct stat *stat, struct dirent *ext,
 		    struct dirent **res)
 {
 	int              ret = 0;
 	gf_dirent_t     *entry = NULL;
+	struct dirent   *buf = NULL;
 
 	__glfs_entry_fd (glfd);
 
 	errno = 0;
+
+	if (ext)
+		buf = ext;
+	else
+		buf = glfs_readdirbuf_get (glfd);
+
+	if (!buf) {
+		errno = ENOMEM;
+		return -1;
+	}
+
 	entry = glfd_entry_next (glfd, !!stat);
 	if (errno)
 		ret = -1;
@@ -2050,6 +2098,28 @@ glfs_readdir_r (struct glfs_fd *glfd, struct dirent *buf, struct dirent **res)
 }
 
 
+struct dirent *
+glfs_readdirplus (struct glfs_fd *glfd, struct stat *stat)
+{
+        struct dirent *res = NULL;
+        int ret = -1;
+
+        ret = glfs_readdirplus_r (glfd, stat, NULL, &res);
+        if (ret)
+                return NULL;
+
+        return res;
+}
+
+
+
+struct dirent *
+glfs_readdir (struct glfs_fd *glfd)
+{
+        return glfs_readdirplus (glfd, NULL);
+}
+
+
 int
 glfs_statvfs (struct glfs *fs, const char *path, struct statvfs *buf)
 {

api/src/glfs-internal.h

@@ -95,6 +95,7 @@ struct glfs_fd {
 	fd_t              *fd; /* Currently guared by @fs->mutex. TODO: per-glfd lock */
 	struct list_head   entries;
 	gf_dirent_t       *next;
+	struct dirent     *readdirbuf;
 };
 
 /* glfs object handle introduced for the alternate gfapi implementation based

api/src/glfs-mem-types.h

@@ -24,6 +24,7 @@ enum glfs_mem_types_ {
 	glfs_mt_volfile_t,
 	glfs_mt_xlator_cmdline_option_t,
 	glfs_mt_glfs_object_t,
+	glfs_mt_readdirbuf_t,
 	glfs_mt_end
 
 };

api/src/glfs.c

@@ -384,6 +384,9 @@ glfs_fd_destroy (struct glfs_fd *glfd)
 
 	if (glfd->fd)
 		fd_unref (glfd->fd);
+
+	GF_FREE (glfd->readdirbuf);
+
 	GF_FREE (glfd);
 }
 

api/src/glfs.h

@@ -468,12 +468,31 @@ int glfs_link (glfs_t *fs, const char *oldpath, const char *newpath);
 
 glfs_fd_t *glfs_opendir (glfs_t *fs, const char *path);
 
+/*
+ * @glfs_readdir_r and @glfs_readdirplus_r ARE thread safe AND re-entrant,
+ * but the interface has ambiguity about the size of @dirent to be allocated
+ * before calling the APIs. 512 byte buffer (for @dirent) is sufficient for
+ * all known systems which are tested againt glusterfs/gfapi, but may be
+ * insufficient in the future.
+ */
+
 int glfs_readdir_r (glfs_fd_t *fd, struct dirent *dirent,
 		    struct dirent **result);
 
 int glfs_readdirplus_r (glfs_fd_t *fd, struct stat *stat, struct dirent *dirent,
 			struct dirent **result);
 
+/*
+ * @glfs_readdir and @glfs_readdirplus are NEITHER thread safe NOR re-entrant
+ * when called on the same directory handle. However they ARE thread safe
+ * AND re-entrant when called on different directory handles (which may be
+ * referring to the same directory too.)
+ */
+
+struct dirent *glfs_readdir (glfs_fd_t *fd);
+
+struct dirent *glfs_readdirplus (glfs_fd_t *fd, struct stat *stat);
+
 long glfs_telldir (glfs_fd_t *fd);
 
 void glfs_seekdir (glfs_fd_t *fd, long offset);