[PATCH v3] f2fs: add fast symlink support

[Wanpeng Li <wanpeng.li@linux.intel.com>]

This patch introduces the improvement fast symlinks to allow storage of
the target path within inode, thus symlinks with short target paths are
more accessed quickly. It will fall back to using the original slow
symlink if the target path exceeds the available inode space.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v2 -> v3:
 * handle fast symlink in remove_inode_page
v1 -> v2:
 * set max size of fast symlink according to inline_xattr flag

 fs/f2fs/f2fs.h          | 15 ++++++++++++++
 fs/f2fs/file.c          |  2 ++
 fs/f2fs/inode.c         |  9 +++++++--
 fs/f2fs/namei.c         | 53 +++++++++++++++++++++++++++++++++++++++++++++----
 fs/f2fs/node.c          |  5 +++--
 include/linux/f2fs_fs.h |  2 ++
 6 files changed, 78 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 511d6cd..3012ea0 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1226,6 +1226,7 @@ enum {
 	FI_VOLATILE_FILE,	/* indicate volatile file */
 	FI_DROP_CACHE,		/* drop dirty page cache */
 	FI_DATA_EXIST,		/* indicate data exists */
+	FI_FAST_SYMLINK,        /* indicate fast symlink */
 };
 
 static inline void set_inode_flag(struct f2fs_inode_info *fi, int flag)
@@ -1262,6 +1263,8 @@ static inline void get_inline_info(struct f2fs_inode_info *fi,
 		set_inode_flag(fi, FI_INLINE_DENTRY);
 	if (ri->i_inline & F2FS_DATA_EXIST)
 		set_inode_flag(fi, FI_DATA_EXIST);
+	if (ri->i_inline & F2FS_FAST_SYMLINK)
+		set_inode_flag(fi, FI_FAST_SYMLINK);
 }
 
 static inline void set_raw_inline(struct f2fs_inode_info *fi,
@@ -1277,6 +1280,8 @@ static inline void set_raw_inline(struct f2fs_inode_info *fi,
 		ri->i_inline |= F2FS_INLINE_DENTRY;
 	if (is_inode_flag_set(fi, FI_DATA_EXIST))
 		ri->i_inline |= F2FS_DATA_EXIST;
+	if (is_inode_flag_set(fi, FI_FAST_SYMLINK))
+		ri->i_inline |= F2FS_FAST_SYMLINK;
 }
 
 static inline int f2fs_has_inline_xattr(struct inode *inode)
@@ -1370,6 +1375,15 @@ static inline void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi)
 	sbi->sb->s_flags |= MS_RDONLY;
 }
 
+/*
+ * Test whether an inode is a fast symlink.
+ */
+static inline int f2fs_inode_is_fast_symlink(struct inode *inode)
+{
+	return (S_ISLNK(inode->i_mode) &&
+			is_inode_flag_set(F2FS_I(inode), FI_FAST_SYMLINK));
+}
+
 #define get_inode_mode(i) \
 	((is_inode_flag_set(F2FS_I(i), FI_ACL_MODE)) ? \
 	 (F2FS_I(i)->i_acl_mode) : ((i)->i_mode))
@@ -1746,6 +1760,7 @@ extern const struct address_space_operations f2fs_node_aops;
 extern const struct address_space_operations f2fs_meta_aops;
 extern const struct inode_operations f2fs_dir_inode_operations;
 extern const struct inode_operations f2fs_symlink_inode_operations;
+extern const struct inode_operations f2fs_fast_symlink_inode_operations;
 extern const struct inode_operations f2fs_special_inode_operations;
 extern struct kmem_cache *inode_entry_slab;
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f1341c7..05a3d4f 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -546,6 +546,8 @@ void f2fs_truncate(struct inode *inode)
 	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
 				S_ISLNK(inode->i_mode)))
 		return;
+	if (f2fs_inode_is_fast_symlink(inode))
+		return;
 
 	trace_f2fs_truncate(inode);
 
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index b508744..ec9ad22 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -13,6 +13,7 @@
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 #include <linux/bitops.h>
+#include <linux/namei.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -188,8 +189,12 @@ make_now:
 		inode->i_mapping->a_ops = &f2fs_dblock_aops;
 		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_HIGH_ZERO);
 	} else if (S_ISLNK(inode->i_mode)) {
-		inode->i_op = &f2fs_symlink_inode_operations;
-		inode->i_mapping->a_ops = &f2fs_dblock_aops;
+		if (f2fs_inode_is_fast_symlink(inode))
+			inode->i_op = &f2fs_fast_symlink_inode_operations;
+		else {
+			inode->i_op = &f2fs_symlink_inode_operations;
+			inode->i_mapping->a_ops = &f2fs_dblock_aops;
+		}
 	} else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
 			S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
 		inode->i_op = &f2fs_special_inode_operations;
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 1e2ae21..0619909 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -14,6 +14,7 @@
 #include <linux/sched.h>
 #include <linux/ctype.h>
 #include <linux/dcache.h>
+#include <linux/namei.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -247,6 +248,21 @@ fail:
 	return err;
 }
 
+static void *f2fs_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+	struct page *node_page;
+
+	node_page = get_node_page(F2FS_I_SB(dentry->d_inode),
+				dentry->d_inode->i_ino);
+	if (IS_ERR(node_page)) {
+		nd_set_link(nd, NULL);
+		return NULL;
+	}
+	nd_set_link(nd, (char *)(F2FS_INODE(node_page)->i_addr));
+	f2fs_put_page(node_page, 1);
+	return NULL;
+}
+
 static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 					const char *symname)
 {
@@ -261,16 +277,31 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 	if (IS_ERR(inode))
 		return PTR_ERR(inode);
 
-	inode->i_op = &f2fs_symlink_inode_operations;
-	inode->i_mapping->a_ops = &f2fs_dblock_aops;
-
 	f2fs_lock_op(sbi);
 	err = f2fs_add_link(dentry, inode);
 	if (err)
 		goto out;
 	f2fs_unlock_op(sbi);
 
-	err = page_symlink(inode, symname, symlen);
+
+	if (symlen > MAX_FAST_SYMLINK_SIZE) {
+		/* slow symlink */
+		inode->i_op = &f2fs_symlink_inode_operations;
+		inode->i_mapping->a_ops = &f2fs_dblock_aops;
+		err = page_symlink(inode, symname, symlen);
+	} else {
+		/* fast symlink */
+		struct page *node_page;
+
+		inode->i_op = &f2fs_fast_symlink_inode_operations;
+		node_page = get_node_page(sbi, inode->i_ino);
+		memcpy((char *)&F2FS_INODE(node_page)->i_addr, symname, symlen);
+		set_page_dirty(node_page);
+		f2fs_put_page(node_page, 1);
+		inode->i_size = symlen-1;
+		set_inode_flag(F2FS_I(inode), FI_FAST_SYMLINK);
+		mark_inode_dirty(inode);
+	}
 	alloc_nid_done(sbi, inode->i_ino);
 
 	d_instantiate(dentry, inode);
@@ -743,6 +774,20 @@ const struct inode_operations f2fs_symlink_inode_operations = {
 #endif
 };
 
+const struct inode_operations f2fs_fast_symlink_inode_operations = {
+	.readlink       = generic_readlink,
+	.follow_link    = f2fs_follow_link,
+	.put_link       = page_put_link,
+	.getattr	= f2fs_getattr,
+	.setattr	= f2fs_setattr,
+#ifdef CONFIG_F2FS_FS_XATTR
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
+	.listxattr	= f2fs_listxattr,
+	.removexattr	= generic_removexattr,
+#endif
+};
+
 const struct inode_operations f2fs_special_inode_operations = {
 	.getattr	= f2fs_getattr,
 	.setattr        = f2fs_setattr,
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 35a9117..efe28a2b 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -908,8 +908,9 @@ void remove_inode_page(struct inode *inode)
 	}
 
 	/* remove potential inline_data blocks */
-	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
-				S_ISLNK(inode->i_mode))
+	if ((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+				S_ISLNK(inode->i_mode)) &&
+				!f2fs_inode_is_fast_symlink(inode))
 		truncate_data_blocks_range(&dn, 1);
 
 	/* 0 is possible, after f2fs_new_inode() has failed */
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 502f28c..834880c 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -178,9 +178,11 @@ struct f2fs_extent {
 #define F2FS_INLINE_DATA	0x02	/* file inline data flag */
 #define F2FS_INLINE_DENTRY	0x04	/* file inline dentry flag */
 #define F2FS_DATA_EXIST		0x08	/* file inline data exist flag */
+#define F2FS_FAST_SYMLINK	0x10    /* file fast symlink flag */
 
 #define MAX_INLINE_DATA		(sizeof(__le32) * (DEF_ADDRS_PER_INODE - \
 						F2FS_INLINE_XATTR_ADDRS - 1))
+#define MAX_FAST_SYMLINK_SIZE (MAX_INLINE_DATA + 1)
 
 struct f2fs_inode {
 	__le16 i_mode;			/* file mode */
-- 
1.9.1