From 7669e8fb09da47dd45c07a51394f01031ea81da8 Mon Sep 17 00:00:00 2001 From: "Steven J. Magnani" Date: Thu, 4 Oct 2012 17:14:45 -0700 Subject: fat (exportfs): fix dentry reconnection Maintain an index of directory inodes by starting cluster, so that fat_get_parent() can return the proper cached inode rather than inventing one that cannot be traced back to the filesystem root. Add a new msdos/vfat binary mount option "nfs" so that FAT filesystems that are _not_ exported via NFS are not saddled with maintenance of an index they will never use. Finally, simplify NFS file handle generation and lookups. An ext2-congruent implementation is adequate for FAT needs. Signed-off-by: Steven J. Magnani Acked-by: OGAWA Hirofumi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fat/nfs.c | 150 ++++++++++++++++++++--------------------------------------- 1 file changed, 50 insertions(+), 100 deletions(-) (limited to 'fs/fat/nfs.c') diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c index 21609a1e9355..ef4b5faba87b 100644 --- a/fs/fat/nfs.c +++ b/fs/fat/nfs.c @@ -14,47 +14,46 @@ #include #include "fat.h" -/* - * a FAT file handle with fhtype 3 is - * 0/ i_ino - for fast, reliable lookup if still in the cache - * 1/ i_generation - to see if i_ino is still valid - * bit 0 == 0 iff directory - * 2/ i_pos(8-39) - if ino has changed, but still in cache - * 3/ i_pos(4-7)|i_logstart - to semi-verify inode found at i_pos - * 4/ i_pos(0-3)|parent->i_logstart - maybe used to hunt for the file on disc - * - * Hack for NFSv2: Maximum FAT entry number is 28bits and maximum - * i_pos is 40bits (blocknr(32) + dir offset(8)), so two 4bits - * of i_logstart is used to store the directory entry offset. +/** + * Look up a directory inode given its starting cluster. */ - -int -fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent) +static struct inode *fat_dget(struct super_block *sb, int i_logstart) { - int len = *lenp; - struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb); - loff_t i_pos; + struct msdos_sb_info *sbi = MSDOS_SB(sb); + struct hlist_head *head; + struct hlist_node *_p; + struct msdos_inode_info *i; + struct inode *inode = NULL; - if (len < 5) { - *lenp = 5; - return 255; /* no room */ + head = sbi->dir_hashtable + fat_dir_hash(i_logstart); + spin_lock(&sbi->dir_hash_lock); + hlist_for_each_entry(i, _p, head, i_dir_hash) { + BUG_ON(i->vfs_inode.i_sb != sb); + if (i->i_logstart != i_logstart) + continue; + inode = igrab(&i->vfs_inode); + if (inode) + break; } - - i_pos = fat_i_pos_read(sbi, inode); - *lenp = 5; - fh[0] = inode->i_ino; - fh[1] = inode->i_generation; - fh[2] = i_pos >> 8; - fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart; - fh[4] = (i_pos & 0x0f) << 28; - if (parent) - fh[4] |= MSDOS_I(parent)->i_logstart; - return 3; + spin_unlock(&sbi->dir_hash_lock); + return inode; } -static int fat_is_valid_fh(int fh_len, int fh_type) +static struct inode *fat_nfs_get_inode(struct super_block *sb, + u64 ino, u32 generation) { - return ((fh_len >= 5) && (fh_type == 3)); + struct inode *inode; + + if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO)) + return NULL; + + inode = ilookup(sb, ino); + if (inode && generation && (inode->i_generation != generation)) { + iput(inode); + inode = NULL; + } + + return inode; } /** @@ -64,57 +63,19 @@ static int fat_is_valid_fh(int fh_len, int fh_type) struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { - struct inode *inode = NULL; - u32 *fh = fid->raw; - loff_t i_pos; - unsigned long i_ino; - __u32 i_generation; - int i_logstart; - - if (!fat_is_valid_fh(fh_len, fh_type)) - return NULL; - - i_ino = fh[0]; - i_generation = fh[1]; - i_logstart = fh[3] & 0x0fffffff; - - /* Try i_ino lookup first - fastest and most reliable */ - inode = ilookup(sb, i_ino); - if (inode && (inode->i_generation != i_generation)) { - iput(inode); - inode = NULL; - } - if (!inode) { - i_pos = (loff_t)fh[2] << 8; - i_pos |= ((fh[3] >> 24) & 0xf0) | (fh[4] >> 28); - - /* try 2 - see if i_pos is in F-d-c - * require i_logstart to be the same - * Will fail if you truncate and then re-write - */ - - inode = fat_iget(sb, i_pos); - if (inode && MSDOS_I(inode)->i_logstart != i_logstart) { - iput(inode); - inode = NULL; - } - } + return generic_fh_to_dentry(sb, fid, fh_len, fh_type, + fat_nfs_get_inode); +} - /* - * For now, do nothing if the inode is not found. - * - * What we could do is: - * - * - follow the file starting at fh[4], and record the ".." entry, - * and the name of the fh[2] entry. - * - then follow the ".." file finding the next step up. - * - * This way we build a path to the root of the tree. If this works, we - * lookup the path and so get this inode into the cache. Finally try - * the fat_iget lookup again. If that fails, then we are totally out - * of luck. But all that is for another day - */ - return d_obtain_alias(inode); +/* + * Find the parent for a file specified by NFS handle. + * This requires that the handle contain the i_ino of the parent. + */ +struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_parent(sb, fid, fh_len, fh_type, + fat_nfs_get_inode); } /* @@ -128,24 +89,13 @@ struct dentry *fat_get_parent(struct dentry *child_dir) struct super_block *sb = child_dir->d_sb; struct buffer_head *bh = NULL; struct msdos_dir_entry *de; - loff_t i_pos; - struct dentry *parent; - struct inode *inode; - int err; + struct inode *parent_inode = NULL; - lock_super(sb); - - err = fat_get_dotdot_entry(child_dir->d_inode, &bh, &de, &i_pos); - if (err) { - parent = ERR_PTR(err); - goto out; + if (!fat_get_dotdot_entry(child_dir->d_inode, &bh, &de)) { + int parent_logstart = fat_get_start(MSDOS_SB(sb), de); + parent_inode = fat_dget(sb, parent_logstart); } - inode = fat_build_inode(sb, de, i_pos); - - parent = d_obtain_alias(inode); -out: brelse(bh); - unlock_super(sb); - return parent; + return d_obtain_alias(parent_inode); } -- cgit v1.2.3