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Date: Sun, 20 Jan 2013 20:06:33 +0900
From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To: Namjae Jeon <linkinjeon@...il.com>
Cc: akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Namjae Jeon <namjae.jeon@...sung.com>,
Ravishankar N <ravi.n1@...sung.com>,
Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v5 7/8] fat (exportfs): rebuild directory-inode if fat_dget() fails
Namjae Jeon <linkinjeon@...il.com> 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@...l.parknet.co.jp>
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