RHEL 7.5 compat: FMODE_KABI_ITERATE

As of RHEL 7.5 the mainline fops.iterate() method was added to
the file_operations structure and is correctly detected by the
configure script.

Normally this is what we want, but in order to maintain KABI
compatibility the RHEL change additionally does the following:

* Requires that callers intending to use this extended interface
  set the FMODE_KABI_ITERATE flag on the file structure when
  opening the directory.
* Adds the fops.iterate() method to the end of the structure,
  without removing fops.readdir().

This change updates the configure check to ignore the RHEL 7.5+
variant of fops.iterate() when detected.  Instead fallback to
the fops.readdir() interface which will be available.

Finally, add the 'zpl_' prefix to the directory context wrappers
to avoid colliding with the kernel provided symbols when both
the fops.iterate() and fops.readdir() are provided by the kernel.

Reviewed-by: Olaf Faaland <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #7460 
Closes #7463 

3 files changed, 27 insertions, 23 deletions

diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 0eeb2bb42..d7d73201d 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -2273,7 +2273,7 @@ out:
  */
 /* ARGSUSED */
 int
-zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
+zfs_readdir(struct inode *ip, zpl_dir_context_t *ctx, cred_t *cr)
 {
 	znode_t		*zp = ITOZ(ip);
 	zfsvfs_t	*zfsvfs = ITOZSB(ip);
@@ -2378,7 +2378,7 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
 			type = ZFS_DIRENT_TYPE(zap.za_first_integer);
 		}
 
-		done = !dir_emit(ctx, zap.za_name, strlen(zap.za_name),
+		done = !zpl_dir_emit(ctx, zap.za_name, strlen(zap.za_name),
 		    objnum, type);
 		if (done)
 			break;
diff --git a/module/zfs/zpl_ctldir.c b/module/zfs/zpl_ctldir.c
index 1c5fb34e6..6df367b81 100644
--- a/module/zfs/zpl_ctldir.c
+++ b/module/zfs/zpl_ctldir.c
@@ -50,27 +50,27 @@ zpl_common_open(struct inode *ip, struct file *filp)
  * Get root directory contents.
  */
 static int
-zpl_root_iterate(struct file *filp, struct dir_context *ctx)
+zpl_root_iterate(struct file *filp, zpl_dir_context_t *ctx)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(file_inode(filp));
 	int error = 0;
 
 	ZFS_ENTER(zfsvfs);
 
-	if (!dir_emit_dots(filp, ctx))
+	if (!zpl_dir_emit_dots(filp, ctx))
 		goto out;
 
 	if (ctx->pos == 2) {
-		if (!dir_emit(ctx, ZFS_SNAPDIR_NAME, strlen(ZFS_SNAPDIR_NAME),
-		    ZFSCTL_INO_SNAPDIR, DT_DIR))
+		if (!zpl_dir_emit(ctx, ZFS_SNAPDIR_NAME,
+		    strlen(ZFS_SNAPDIR_NAME), ZFSCTL_INO_SNAPDIR, DT_DIR))
 			goto out;
 
 		ctx->pos++;
 	}
 
 	if (ctx->pos == 3) {
-		if (!dir_emit(ctx, ZFS_SHAREDIR_NAME, strlen(ZFS_SHAREDIR_NAME),
-		    ZFSCTL_INO_SHARES, DT_DIR))
+		if (!zpl_dir_emit(ctx, ZFS_SHAREDIR_NAME,
+		    strlen(ZFS_SHAREDIR_NAME), ZFSCTL_INO_SHARES, DT_DIR))
 			goto out;
 
 		ctx->pos++;
@@ -85,7 +85,8 @@ out:
 static int
 zpl_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
-	struct dir_context ctx = DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
+	zpl_dir_context_t ctx =
+	    ZPL_DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
 	int error;
 
 	error = zpl_root_iterate(filp, &ctx);
@@ -93,7 +94,7 @@ zpl_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 	return (error);
 }
-#endif /* HAVE_VFS_ITERATE */
+#endif /* !HAVE_VFS_ITERATE && !HAVE_VFS_ITERATE_SHARED */
 
 /*
  * Get root directory attributes.
@@ -248,7 +249,7 @@ zpl_snapdir_lookup(struct inode *dip, struct dentry *dentry,
 }
 
 static int
-zpl_snapdir_iterate(struct file *filp, struct dir_context *ctx)
+zpl_snapdir_iterate(struct file *filp, zpl_dir_context_t *ctx)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(file_inode(filp));
 	fstrans_cookie_t cookie;
@@ -260,7 +261,7 @@ zpl_snapdir_iterate(struct file *filp, struct dir_context *ctx)
 	ZFS_ENTER(zfsvfs);
 	cookie = spl_fstrans_mark();
 
-	if (!dir_emit_dots(filp, ctx))
+	if (!zpl_dir_emit_dots(filp, ctx))
 		goto out;
 
 	pos = ctx->pos;
@@ -272,7 +273,7 @@ zpl_snapdir_iterate(struct file *filp, struct dir_context *ctx)
 		if (error)
 			goto out;
 
-		if (!dir_emit(ctx, snapname, strlen(snapname),
+		if (!zpl_dir_emit(ctx, snapname, strlen(snapname),
 		    ZFSCTL_INO_SHARES - id, DT_DIR))
 			goto out;
 
@@ -292,7 +293,8 @@ out:
 static int
 zpl_snapdir_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
-	struct dir_context ctx = DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
+	zpl_dir_context_t ctx =
+	    ZPL_DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
 	int error;
 
 	error = zpl_snapdir_iterate(filp, &ctx);
@@ -300,7 +302,7 @@ zpl_snapdir_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 	return (error);
 }
-#endif /* HAVE_VFS_ITERATE */
+#endif /* !HAVE_VFS_ITERATE && !HAVE_VFS_ITERATE_SHARED */
 
 static int
 zpl_snapdir_rename2(struct inode *sdip, struct dentry *sdentry,
@@ -463,7 +465,7 @@ zpl_shares_lookup(struct inode *dip, struct dentry *dentry,
 }
 
 static int
-zpl_shares_iterate(struct file *filp, struct dir_context *ctx)
+zpl_shares_iterate(struct file *filp, zpl_dir_context_t *ctx)
 {
 	fstrans_cookie_t cookie;
 	cred_t *cr = CRED();
@@ -475,7 +477,7 @@ zpl_shares_iterate(struct file *filp, struct dir_context *ctx)
 	cookie = spl_fstrans_mark();
 
 	if (zfsvfs->z_shares_dir == 0) {
-		dir_emit_dots(filp, ctx);
+		zpl_dir_emit_dots(filp, ctx);
 		goto out;
 	}
 
@@ -500,7 +502,8 @@ out:
 static int
 zpl_shares_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
-	struct dir_context ctx = DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
+	zpl_dir_context_t ctx =
+	    ZPL_DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
 	int error;
 
 	error = zpl_shares_iterate(filp, &ctx);
@@ -508,7 +511,7 @@ zpl_shares_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 	return (error);
 }
-#endif /* HAVE_VFS_ITERATE */
+#endif /* !HAVE_VFS_ITERATE && !HAVE_VFS_ITERATE_SHARED */
 
 /* ARGSUSED */
 static int
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c
index 1c5f5e409..e03a0481c 100644
--- a/module/zfs/zpl_file.c
+++ b/module/zfs/zpl_file.c
@@ -76,7 +76,7 @@ zpl_release(struct inode *ip, struct file *filp)
 }
 
 static int
-zpl_iterate(struct file *filp, struct dir_context *ctx)
+zpl_iterate(struct file *filp, zpl_dir_context_t *ctx)
 {
 	cred_t *cr = CRED();
 	int error;
@@ -96,7 +96,8 @@ zpl_iterate(struct file *filp, struct dir_context *ctx)
 static int
 zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
-	struct dir_context ctx = DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
+	zpl_dir_context_t ctx =
+	    ZPL_DIR_CONTEXT_INIT(dirent, filldir, filp->f_pos);
 	int error;
 
 	error = zpl_iterate(filp, &ctx);
@@ -104,7 +105,7 @@ zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 	return (error);
 }
-#endif /* HAVE_VFS_ITERATE */
+#endif /* !HAVE_VFS_ITERATE && !HAVE_VFS_ITERATE_SHARED */
 
 #if defined(HAVE_FSYNC_WITH_DENTRY)
 /*
@@ -965,7 +966,7 @@ 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_SHARED
+#if defined(HAVE_VFS_ITERATE_SHARED)
 	.iterate_shared	= zpl_iterate,
 #elif defined(HAVE_VFS_ITERATE)
 	.iterate	= zpl_iterate,