Linux 4.7 compat: use iterate_shared for concurrent readdir

Register iterate_shared if it exists so the kernel will used shared
lock and allowing concurrent readdir.

Also, use shared lock when doing llseek with SEEK_DATA or SEEK_HOLE
to allow concurrent seeking.

Signed-off-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #4664
Closes #4665

4 files changed, 54 insertions, 25 deletions

diff --git a/config/kernel-vfs-iterate.m4 b/config/kernel-vfs-iterate.m4
index c2c65622c..7b1599e13 100644
--- a/config/kernel-vfs-iterate.m4
+++ b/config/kernel-vfs-iterate.m4
@@ -1,8 +1,8 @@
-dnl #
-dnl # 3.11 API change
-dnl #
 AC_DEFUN([ZFS_AC_KERNEL_VFS_ITERATE], [
-	AC_MSG_CHECKING([whether fops->iterate() is available])
+	dnl #
+	dnl # 4.7 API change
+	dnl #
+	AC_MSG_CHECKING([whether fops->iterate_shared() is available])
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/fs.h>
 		int iterate(struct file *filp, struct dir_context * context)
@@ -10,34 +10,55 @@ AC_DEFUN([ZFS_AC_KERNEL_VFS_ITERATE], [
 
 		static const struct file_operations fops
 		    __attribute__ ((unused)) = {
-			.iterate	 = iterate,
+			.iterate_shared	 = iterate,
 		};
 	],[
 	],[
 		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_VFS_ITERATE, 1,
-		          [fops->iterate() is available])
+		AC_DEFINE(HAVE_VFS_ITERATE_SHARED, 1,
+		          [fops->iterate_shared() is available])
 	],[
 		AC_MSG_RESULT(no)
 
-		AC_MSG_CHECKING([whether fops->readdir() is available])
+		dnl #
+		dnl # 3.11 API change
+		dnl #
+		AC_MSG_CHECKING([whether fops->iterate() is available])
 		ZFS_LINUX_TRY_COMPILE([
 			#include <linux/fs.h>
-			int readdir(struct file *filp, void *entry, filldir_t func)
+			int iterate(struct file *filp, struct dir_context * context)
 			    { return 0; }
 
 			static const struct file_operations fops
 			    __attribute__ ((unused)) = {
-				.readdir = readdir,
+				.iterate	 = iterate,
 			};
 		],[
 		],[
 			AC_MSG_RESULT(yes)
-			AC_DEFINE(HAVE_VFS_READDIR, 1,
-				  [fops->readdir() is available])
+			AC_DEFINE(HAVE_VFS_ITERATE, 1,
+				  [fops->iterate() is available])
 		],[
-			AC_MSG_ERROR(no; file a bug report with ZFSOnLinux)
-		])
+			AC_MSG_RESULT(no)
+
+			AC_MSG_CHECKING([whether fops->readdir() is available])
+			ZFS_LINUX_TRY_COMPILE([
+				#include <linux/fs.h>
+				int readdir(struct file *filp, void *entry, filldir_t func)
+				    { return 0; }
 
+				static const struct file_operations fops
+				    __attribute__ ((unused)) = {
+					.readdir = readdir,
+				};
+			],[
+			],[
+				AC_MSG_RESULT(yes)
+				AC_DEFINE(HAVE_VFS_READDIR, 1,
+					  [fops->readdir() is available])
+			],[
+				AC_MSG_ERROR(no; file a bug report with ZFSOnLinux)
+			])
+		])
 	])
 ])
diff --git a/include/sys/zpl.h b/include/sys/zpl.h
index 54b35e02d..c6085481b 100644
--- a/include/sys/zpl.h
+++ b/include/sys/zpl.h
@@ -123,7 +123,7 @@ extern const struct inode_operations zpl_ops_snapdirs;
 extern const struct file_operations zpl_fops_shares;
 extern const struct inode_operations zpl_ops_shares;
 
-#ifdef HAVE_VFS_ITERATE
+#if defined(HAVE_VFS_ITERATE) || defined(HAVE_VFS_ITERATE_SHARED)
 
 #define	DIR_CONTEXT_INIT(_dirent, _actor, _pos) {	\
 	.actor = _actor,				\
diff --git a/module/zfs/zpl_ctldir.c b/module/zfs/zpl_ctldir.c
index dd02e9e99..069834eae 100644
--- a/module/zfs/zpl_ctldir.c
+++ b/module/zfs/zpl_ctldir.c
@@ -81,7 +81,7 @@ out:
 	return (error);
 }
 
-#if !defined(HAVE_VFS_ITERATE)
+#if !defined(HAVE_VFS_ITERATE) && !defined(HAVE_VFS_ITERATE_SHARED)
 static int
 zpl_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
@@ -144,7 +144,9 @@ const struct file_operations zpl_fops_root = {
 	.open		= zpl_common_open,
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
-#ifdef HAVE_VFS_ITERATE
+#ifdef HAVE_VFS_ITERATE_SHARED
+	.iterate_shared	= zpl_root_iterate,
+#elif defined(HAVE_VFS_ITERATE)
 	.iterate	= zpl_root_iterate,
 #else
 	.readdir	= zpl_root_readdir,
@@ -285,7 +287,7 @@ out:
 	return (error);
 }
 
-#if !defined(HAVE_VFS_ITERATE)
+#if !defined(HAVE_VFS_ITERATE) && !defined(HAVE_VFS_ITERATE_SHARED)
 static int
 zpl_snapdir_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
@@ -385,7 +387,9 @@ const struct file_operations zpl_fops_snapdir = {
 	.open		= zpl_common_open,
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
-#ifdef HAVE_VFS_ITERATE
+#ifdef HAVE_VFS_ITERATE_SHARED
+	.iterate_shared	= zpl_snapdir_iterate,
+#elif defined(HAVE_VFS_ITERATE)
 	.iterate	= zpl_snapdir_iterate,
 #else
 	.readdir	= zpl_snapdir_readdir,
@@ -472,7 +476,7 @@ out:
 	return (error);
 }
 
-#if !defined(HAVE_VFS_ITERATE)
+#if !defined(HAVE_VFS_ITERATE) && !defined(HAVE_VFS_ITERATE_SHARED)
 static int
 zpl_shares_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
@@ -525,7 +529,9 @@ const struct file_operations zpl_fops_shares = {
 	.open		= zpl_common_open,
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
-#ifdef HAVE_VFS_ITERATE
+#ifdef HAVE_VFS_ITERATE_SHARED
+	.iterate_shared	= zpl_shares_iterate,
+#elif defined(HAVE_VFS_ITERATE)
 	.iterate	= zpl_shares_iterate,
 #else
 	.readdir	= zpl_shares_readdir,
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c
index 36153cb90..4481237bc 100644
--- a/module/zfs/zpl_file.c
+++ b/module/zfs/zpl_file.c
@@ -93,7 +93,7 @@ zpl_iterate(struct file *filp, struct dir_context *ctx)
 	return (error);
 }
 
-#if !defined(HAVE_VFS_ITERATE)
+#if !defined(HAVE_VFS_ITERATE) && !defined(HAVE_VFS_ITERATE_SHARED)
 static int
 zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
@@ -421,13 +421,13 @@ zpl_llseek(struct file *filp, loff_t offset, int whence)
 		loff_t maxbytes = ip->i_sb->s_maxbytes;
 		loff_t error;
 
-		spl_inode_lock(ip);
+		spl_inode_lock_shared(ip);
 		cookie = spl_fstrans_mark();
 		error = -zfs_holey(ip, whence, &offset);
 		spl_fstrans_unmark(cookie);
 		if (error == 0)
 			error = lseek_execute(filp, ip, offset, maxbytes);
-		spl_inode_unlock(ip);
+		spl_inode_unlock_shared(ip);
 
 		return (error);
 	}
@@ -853,7 +853,9 @@ const struct file_operations zpl_file_operations = {
 const struct file_operations zpl_dir_file_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
-#ifdef HAVE_VFS_ITERATE
+#ifdef HAVE_VFS_ITERATE_SHARED
+	.iterate_shared	= zpl_iterate,
+#elif defined(HAVE_VFS_ITERATE)
 	.iterate	= zpl_iterate,
 #else
 	.readdir	= zpl_readdir,