Re: [PATCH v5 7/8] fat (exportfs): rebuild directory-inode if fat_dget() fails

[OGAWA Hirofumi]

Namjae Jeon <linkinjeon@xxxxxxxxx> writes:

> We rewrite patch as your suggestion using dummy inode. Would please
> you review below patch code ?

Looks like good as initial. Clean and shorter.

Next is, we have to think about race. I.e. if real inode was made, what
happens? Is there no race?

Thanks.

> Subject: [PATCH] fat (exportfs): rebuild directory-inode if fat_dget()
>  fails
>
> This patch enables rebuilding of directory inodes which are not present
> in the cache.This is done by traversing the disk clusters to find the
> directory entry of the parent directory and using its i_pos to build the
> inode.
>
> Do this only if the "nostale_ro" nfs mount option is specified.
>
> ---
>  fs/fat/dir.c   |   23 +++++++++++++++++++++++
>  fs/fat/fat.h   |    3 +++
>  fs/fat/inode.c |    2 +-
>  fs/fat/nfs.c   |   52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  4 files changed, 78 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> index 695c15c..ac97f34 100644
> --- a/fs/fat/dir.c
> +++ b/fs/fat/dir.c
> @@ -975,6 +975,29 @@ int fat_scan(struct inode *dir, const unsigned char *name,
>
>  EXPORT_SYMBOL_GPL(fat_scan);
>
> +/*
> + * Scans a directory for a given logstart.
> + * Returns an error code or zero.
> + */
> +int fat_scan_logstart(struct inode *dir, int i_logstart,
> +		      struct fat_slot_info *sinfo)
> +{
> +	struct super_block *sb = dir->i_sb;
> +
> +	sinfo->slot_off = 0;
> +	sinfo->bh = NULL;
> +	while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
> +				   &sinfo->de) >= 0) {
> +		if (fat_get_start(MSDOS_SB(sb), sinfo->de) == i_logstart) {
> +			sinfo->slot_off -= sizeof(*sinfo->de);
> +			sinfo->nr_slots = 1;
> +			sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
> +			return 0;
> +		}
> +	}
> +	return -ENOENT;
> +}
> +
>  static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
>  {
>  	struct super_block *sb = dir->i_sb;
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index 73f15b8..d882c01 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -291,6 +291,8 @@ extern int fat_dir_empty(struct inode *dir);
>  extern int fat_subdirs(struct inode *dir);
>  extern int fat_scan(struct inode *dir, const unsigned char *name,
>  		    struct fat_slot_info *sinfo);
> +extern int fat_scan_logstart(struct inode *dir, int i_logstart,
> +			     struct fat_slot_info *sinfo);
>  extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
>  				struct msdos_dir_entry **de);
>  extern int fat_alloc_new_dir(struct inode *dir, struct timespec *ts);
> @@ -370,6 +372,7 @@ extern int fat_fill_super(struct super_block *sb,
> void *data, int silent,
>
>  extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
>  		            struct inode *i2);
> +extern int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de);
>  static inline unsigned long fat_dir_hash(int logstart)
>  {
>  	return hash_32(logstart, FAT_HASH_BITS);
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index 491320b..c4c286a 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -384,7 +384,7 @@ static int fat_calc_dir_size(struct inode *inode)
>  }
>
>  /* doesn't deal with root inode */
> -static int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
> +int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
>  {
>  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
>  	int error;
> diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
> index 08ff9fa..e94da33 100644
> --- a/fs/fat/nfs.c
> +++ b/fs/fat/nfs.c
> @@ -213,6 +213,53 @@ static struct dentry
> *fat_fh_to_parent_nostale(struct super_block *sb,
>  }
>
>  /*
> + * Rebuild the parent for a directory that is not connected
> + *  to the filesystem root
> + */
> +static
> +struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
> +{
> +	int search_clus, clus_to_match;
> +	struct msdos_dir_entry *de;
> +	struct inode *parent = NULL;
> +	struct inode *dummy_grand_parent = NULL;
> +	struct fat_slot_info sinfo;
> +	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> +	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
> +	struct buffer_head *parent_bh = sb_bread(sb, blknr);
> +	if (!parent_bh) {
> +		fat_msg(sb, KERN_ERR,
> +			"unable to read cluster of parent directory");
> +		return NULL;
> +	}
> +
> +	de = (struct msdos_dir_entry *) parent_bh->b_data;
> +	clus_to_match = fat_get_start(sbi, &de[0]);
> +	search_clus = fat_get_start(sbi, &de[1]);
> +
> +	dummy_grand_parent = fat_dget(sb, search_clus);
> +	if (!dummy_grand_parent) {
> +		dummy_grand_parent = new_inode(sb);
> +		if (!dummy_grand_parent) {
> +			brelse(parent_bh);
> +			return parent;
> +		}
> +
> +		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
> +		fat_fill_inode(dummy_grand_parent, &de[1]);
> +		MSDOS_I(dummy_grand_parent)->i_pos = -1;
> +	}
> +
> +	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
> +		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
> +
> +	brelse(parent_bh);
> +	iput(dummy_grand_parent);
> +
> +	return parent;
> +}
> +
> +/*
>   * Find the parent for a directory that is not currently connected to
>   * the filesystem root.
>   *
> @@ -224,10 +271,13 @@ static struct dentry *fat_get_parent(struct
> dentry *child_dir)
>  	struct buffer_head *bh = NULL;
>  	struct msdos_dir_entry *de;
>  	struct inode *parent_inode = NULL;
> +	struct msdos_sb_info *sbi = MSDOS_SB(sb);
>
>  	if (!fat_get_dotdot_entry(child_dir->d_inode, &bh, &de)) {
> -		int parent_logstart = fat_get_start(MSDOS_SB(sb), de);
> +		int parent_logstart = fat_get_start(sbi, de);
>  		parent_inode = fat_dget(sb, parent_logstart);
> +		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
> +			parent_inode = fat_rebuild_parent(sb, parent_logstart);
>  	}
>  	brelse(bh);

-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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