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Message-ID: <878v9f5ugn.fsf@devron.myhome.or.jp>
Date: Mon, 03 Dec 2012 18:57:28 +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:
> From: Namjae Jeon <namjae.jeon@...sung.com>
>
> 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.
This became much better than before. However, we have to consolidate the
code with fat_search_long() finally.
E.g. this version is having the issue already fixed. If there is
corruption in fat cluster-chain, it lead to infinite
loop. fat_get_cluster() checks infinite loop by limit.
> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> Signed-off-by: Ravishankar N <ravi.n1@...sung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
> ---
> fs/fat/nfs.c | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 118 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
> index 898bef4..6a9933a 100644
> --- a/fs/fat/nfs.c
> +++ b/fs/fat/nfs.c
> @@ -211,6 +211,120 @@ static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
> }
>
> /*
> + * Read the directory entries of 'search_clus' and find the entry
> + * which contains 'match_ipos' for the starting cluster.If the entry
> + * is found, rebuild its inode.
> + */
> +static struct inode *fat_traverse_cluster(struct super_block *sb,
> + int search_clus, int match_ipos)
> +{
> + struct msdos_sb_info *sbi = MSDOS_SB(sb);
> + struct buffer_head *bh;
> + sector_t blknr;
> + int parent_ipos, search_ipos;
> + int i;
> + struct msdos_dir_entry *de;
> + struct inode *inode = NULL;
> + int iterations = sbi->cluster_size >> sb->s_blocksize_bits;
> + blknr = fat_clus_to_blknr(sbi, search_clus);
> +
> + do {
> + bh = sb_bread(sb, blknr);
> + if (!bh) {
> + fat_msg(sb, KERN_ERR,
> + "NFS:unable to read block(%llu) while traversing cluster(%d)",
> + (llu)blknr, search_clus);
> + inode = ERR_PTR(-EIO);
> + goto out;
> + }
> + de = (struct msdos_dir_entry *)bh->b_data;
> + for (i = 0; i < sbi->dir_per_block; i++) {
> + if (de[i].name[0] == FAT_ENT_FREE) {
> + /*Reached end of directory*/
> + brelse(bh);
> + inode = ERR_PTR(-ENODATA);
> + goto out;
> + }
> + if (de[i].name[0] == DELETED_FLAG)
> + continue;
> + if (de[i].attr == ATTR_EXT)
> + continue;
> + if (!(de[i].attr & ATTR_DIR))
> + continue;
> + else {
> + search_ipos = fat_get_start(sbi, &de[i]);
> + if (search_ipos == match_ipos) {
> + /*Success.Now build the inode*/
> + parent_ipos = (loff_t)i +
> + (blknr << sbi->dir_per_block_bits);
> + inode = fat_build_inode(sb, &de[i],
> + parent_ipos);
> + brelse(bh);
> + goto out;
> + }
> + }
> + }
> + brelse(bh);
> + blknr += 1;
> + } while (--iterations > 0);
> +out:
> + return inode;
> +}
> +
> +/*
> + * 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;
> + struct fat_entry fatent;
> + 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,
> + "NFS: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]);
> + if (!search_clus) {
> + if (sbi->fat_bits == 32)
> + search_clus = sbi->root_cluster;
> + else
> + /* sbi->root_cluster is valid only for FAT32.
> + * Compute search_cluster such that when
> + * fat_traverse_cluster() is called for FAT 12/16,
> + * fat_clus_to_blknr() in it gives us sbi->dir_start
> + */
> + search_clus = ((int)(sbi->dir_start - sbi->data_start)
> + >> ilog2(sbi->sec_per_clus))
> + + FAT_START_ENT;
> + }
> + brelse(parent_bh);
> + do {
> + parent = fat_traverse_cluster(sb,
> + search_clus, clus_to_match);
> + if (IS_ERR(parent) || parent)
> + break;
> + fatent_init(&fatent);
> + search_clus = fat_ent_read(sb, &fatent, search_clus);
> + fatent_brelse(&fatent);
> + if (search_clus < 0 || search_clus == FAT_ENT_FREE)
> + break;
> + } while (search_clus != FAT_ENT_EOF);
> +
> + return parent;
> +
> +}
> +
> +/*
> * Find the parent for a directory that is not currently connected to
> * the filesystem root.
> *
> @@ -222,10 +336,13 @@ 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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