RE: [PATCH RFC] f2fs: add fast symlink

[Chao Yu <chao2.yu@samsung.com>]

Hi Wanpeng,

> -----Original Message-----
> From: Wanpeng Li [mailto:wanpeng.li@linux.intel.com]
> Sent: Wednesday, March 11, 2015 7:52 PM
> To: Jaegeuk Kim
> Cc: Changman Lee; Chao Yu; linux-f2fs-devel@lists.sourceforge.net;
> linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; Wanpeng Li
> Subject: [PATCH RFC] f2fs: add fast symlink
> 
> This patch add fast symlink for f2fs, I'm not sure if inline
> interference with fast symlink, f2fs_follow_link can't be called
> in my patch, so my patch still can't work correctly, please help
> review and give comments to help me out.
> 
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  fs/f2fs/f2fs.h  |  9 +++++++++
>  fs/f2fs/file.c  |  2 ++
>  fs/f2fs/inode.c | 15 +++++++++++++--
>  fs/f2fs/namei.c | 44 +++++++++++++++++++++++++++++++++++++++++---
>  4 files changed, 65 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 511d6cd..5938318 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1370,6 +1370,14 @@ 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) && inode->i_blocks == 0);

How about introducing FI_FAST_SYMLINK & F2FS_FAST_SYMLINK to indicate whether
the inode is fast symlink or not?

So here could be:
	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 +1754,7 @@ 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..627fe6b 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 +189,18 @@ 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)) {
> +			struct page *node_page;
> +
> +			node_page = get_node_page(sbi, inode->i_ino);
> +			inode->i_op = &f2fs_fast_symlink_inode_operations;
> +			nd_terminate_link(F2FS_INODE(node_page)->i_addr,
> +				inode->i_size,
> +				sizeof(F2FS_INODE(node_page)->i_addr) - 1);

I don't think nd_terminate_link() is necessary because we have already copied
terminate char '\0' when creating fast symlink.

> +		} 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..ffc0d52 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 +248,16 @@ 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);

get_node_page can fail, we should handle this.

> +	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)
>  {
> @@ -254,6 +265,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
>  	struct inode *inode;
>  	size_t symlen = strlen(symname) + 1;
>  	int err;
> +	struct page *node_page;
> 
>  	f2fs_balance_fs(sbi);
> 
> @@ -261,16 +273,28 @@ 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;
> 
> +	clear_inode_flag(F2FS_I(inode), FI_INLINE_DATA);
> +	clear_inode_flag(F2FS_I(inode), FI_INLINE_DENTRY);

These flags can't be set, so we can remove them.

>  	f2fs_lock_op(sbi);
>  	err = f2fs_add_link(dentry, inode);
>  	if (err)
>  		goto out;
>  	f2fs_unlock_op(sbi);
> 
> -	err = page_symlink(inode, symname, symlen);
> +	node_page = get_node_page(sbi, inode->i_ino);

move it to below.

> +
> +	if (symlen > sizeof(F2FS_INODE(node_page)->i_addr)) {

We always remain space in inode page for inline xattr data,
so it's better to define our max size of fast symlink as below:

#define MAX_FAST_SYMLINK_SIZE	(MAX_INLINE_DATA + 1)

> +		/* 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 */
> +		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);

Thanks,

> +	}
>  	alloc_nid_done(sbi, inode->i_ino);
> 
>  	d_instantiate(dentry, inode);
> @@ -743,6 +767,20 @@ 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,
> --
> 2.1.0