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 <steve@digidescorp.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
index 21609a1..ef4b5fa 100644
--- a/fs/fat/nfs.c
+++ b/fs/fat/nfs.c
@@ -14,47 +14,46 @@
#include <linux/exportfs.h>
#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 @@
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;
+ return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+ fat_nfs_get_inode);
+}
- 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;
- }
- }
-
- /*
- * 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 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);
}