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/dir.c b/fs/fat/dir.c
index d70d8f3..55e088c 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -872,21 +872,23 @@
}
/*
- * The ".." entry can not provide the "struct fat_slot_info" informations
- * for inode. So, this function provide the some informations only.
+ * The ".." entry can not provide the "struct fat_slot_info" information
+ * for inode, nor a usable i_pos. So, this function provides some information
+ * only.
+ *
+ * Since this function walks through the on-disk inodes within a directory,
+ * callers are responsible for taking any locks necessary to prevent the
+ * directory from changing.
*/
int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
- struct msdos_dir_entry **de, loff_t *i_pos)
+ struct msdos_dir_entry **de)
{
- loff_t offset;
+ loff_t offset = 0;
- offset = 0;
- *bh = NULL;
+ *de = NULL;
while (fat_get_short_entry(dir, &offset, bh, de) >= 0) {
- if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME)) {
- *i_pos = fat_make_i_pos(dir->i_sb, *bh, *de);
+ if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME))
return 0;
- }
}
return -ENOENT;
}
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index fb95939..ec54c3a 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -5,6 +5,7 @@
#include <linux/string.h>
#include <linux/nls.h>
#include <linux/fs.h>
+#include <linux/hash.h>
#include <linux/mutex.h>
#include <linux/ratelimit.h>
#include <linux/msdos_fs.h>
@@ -46,7 +47,8 @@
usefree:1, /* Use free_clusters for FAT32 */
tz_utc:1, /* Filesystem timestamps are in UTC */
rodir:1, /* allow ATTR_RO for directory */
- discard:1; /* Issue discard requests on deletions */
+ discard:1, /* Issue discard requests on deletions */
+ nfs:1; /* Do extra work needed for NFS export */
};
#define FAT_HASH_BITS 8
@@ -88,6 +90,9 @@
spinlock_t inode_hash_lock;
struct hlist_head inode_hashtable[FAT_HASH_SIZE];
+
+ spinlock_t dir_hash_lock;
+ struct hlist_head dir_hashtable[FAT_HASH_SIZE];
};
#define FAT_CACHE_VALID 0 /* special case for valid cache */
@@ -110,6 +115,7 @@
int i_attrs; /* unused attribute bits */
loff_t i_pos; /* on-disk position of directory entry or 0 */
struct hlist_node i_fat_hash; /* hash by i_location */
+ struct hlist_node i_dir_hash; /* hash by i_logstart */
struct rw_semaphore truncate_lock; /* protect bmap against truncate */
struct inode vfs_inode;
};
@@ -262,7 +268,7 @@
extern int fat_scan(struct inode *dir, const unsigned char *name,
struct fat_slot_info *sinfo);
extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
- struct msdos_dir_entry **de, loff_t *i_pos);
+ struct msdos_dir_entry **de);
extern int fat_alloc_new_dir(struct inode *dir, struct timespec *ts);
extern int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
struct fat_slot_info *sinfo);
@@ -341,18 +347,9 @@
extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
struct inode *i2);
-static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
- struct inode *inode)
+static inline unsigned long fat_dir_hash(int logstart)
{
- loff_t i_pos;
-#if BITS_PER_LONG == 32
- spin_lock(&sbi->inode_hash_lock);
-#endif
- i_pos = MSDOS_I(inode)->i_pos;
-#if BITS_PER_LONG == 32
- spin_unlock(&sbi->inode_hash_lock);
-#endif
- return i_pos;
+ return hash_32(logstart, FAT_HASH_BITS);
}
/* fat/misc.c */
@@ -382,10 +379,10 @@
/* fat/nfs.c */
struct fid;
-extern int fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp,
- struct inode *parent);
extern struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type);
+extern struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type);
extern struct dentry *fat_get_parent(struct dentry *child_dir);
/* helper for printk */
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 169f6eb..5741b11 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -281,15 +281,42 @@
return hash_32(i_pos, FAT_HASH_BITS);
}
+static void dir_hash_init(struct super_block *sb)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ int i;
+
+ spin_lock_init(&sbi->dir_hash_lock);
+ for (i = 0; i < FAT_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&sbi->dir_hashtable[i]);
+}
+
void fat_attach(struct inode *inode, loff_t i_pos)
{
struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
- struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
- spin_lock(&sbi->inode_hash_lock);
- MSDOS_I(inode)->i_pos = i_pos;
- hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
- spin_unlock(&sbi->inode_hash_lock);
+ if (inode->i_ino != MSDOS_ROOT_INO) {
+ struct hlist_head *head = sbi->inode_hashtable
+ + fat_hash(i_pos);
+
+ spin_lock(&sbi->inode_hash_lock);
+ MSDOS_I(inode)->i_pos = i_pos;
+ hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
+ spin_unlock(&sbi->inode_hash_lock);
+ }
+
+ /* If NFS support is enabled, cache the mapping of start cluster
+ * to directory inode. This is used during reconnection of
+ * dentries to the filesystem root.
+ */
+ if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
+ struct hlist_head *d_head = sbi->dir_hashtable;
+ d_head += fat_dir_hash(MSDOS_I(inode)->i_logstart);
+
+ spin_lock(&sbi->dir_hash_lock);
+ hlist_add_head(&MSDOS_I(inode)->i_dir_hash, d_head);
+ spin_unlock(&sbi->dir_hash_lock);
+ }
}
EXPORT_SYMBOL_GPL(fat_attach);
@@ -300,6 +327,12 @@
MSDOS_I(inode)->i_pos = 0;
hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
spin_unlock(&sbi->inode_hash_lock);
+
+ if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
+ spin_lock(&sbi->dir_hash_lock);
+ hlist_del_init(&MSDOS_I(inode)->i_dir_hash);
+ spin_unlock(&sbi->dir_hash_lock);
+ }
}
EXPORT_SYMBOL_GPL(fat_detach);
@@ -504,6 +537,7 @@
ei->cache_valid_id = FAT_CACHE_VALID + 1;
INIT_LIST_HEAD(&ei->cache_lru);
INIT_HLIST_NODE(&ei->i_fat_hash);
+ INIT_HLIST_NODE(&ei->i_dir_hash);
inode_init_once(&ei->vfs_inode);
}
@@ -562,6 +596,20 @@
return 0;
}
+static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
+ struct inode *inode)
+{
+ loff_t i_pos;
+#if BITS_PER_LONG == 32
+ spin_lock(&sbi->inode_hash_lock);
+#endif
+ i_pos = MSDOS_I(inode)->i_pos;
+#if BITS_PER_LONG == 32
+ spin_unlock(&sbi->inode_hash_lock);
+#endif
+ return i_pos;
+}
+
static int __fat_write_inode(struct inode *inode, int wait)
{
struct super_block *sb = inode->i_sb;
@@ -655,8 +703,8 @@
};
static const struct export_operations fat_export_ops = {
- .encode_fh = fat_encode_fh,
.fh_to_dentry = fat_fh_to_dentry,
+ .fh_to_parent = fat_fh_to_parent,
.get_parent = fat_get_parent,
};
@@ -706,6 +754,8 @@
seq_puts(m, ",usefree");
if (opts->quiet)
seq_puts(m, ",quiet");
+ if (opts->nfs)
+ seq_puts(m, ",nfs");
if (opts->showexec)
seq_puts(m, ",showexec");
if (opts->sys_immutable)
@@ -750,7 +800,7 @@
Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
Opt_obsolete, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err_cont,
- Opt_err_panic, Opt_err_ro, Opt_discard, Opt_err,
+ Opt_err_panic, Opt_err_ro, Opt_discard, Opt_nfs, Opt_err,
};
static const match_table_t fat_tokens = {
@@ -779,6 +829,7 @@
{Opt_err_panic, "errors=panic"},
{Opt_err_ro, "errors=remount-ro"},
{Opt_discard, "discard"},
+ {Opt_nfs, "nfs"},
{Opt_obsolete, "conv=binary"},
{Opt_obsolete, "conv=text"},
{Opt_obsolete, "conv=auto"},
@@ -859,6 +910,7 @@
opts->numtail = 1;
opts->usefree = opts->nocase = 0;
opts->tz_utc = 0;
+ opts->nfs = 0;
opts->errors = FAT_ERRORS_RO;
*debug = 0;
@@ -1023,6 +1075,9 @@
case Opt_discard:
opts->discard = 1;
break;
+ case Opt_nfs:
+ opts->nfs = 1;
+ break;
/* obsolete mount options */
case Opt_obsolete:
@@ -1313,6 +1368,7 @@
/* set up enough so that it can read an inode */
fat_hash_init(sb);
+ dir_hash_init(sb);
fat_ent_access_init(sb);
/*
@@ -1367,6 +1423,7 @@
}
error = -ENOMEM;
insert_inode_hash(root_inode);
+ fat_attach(root_inode, 0);
sb->s_root = d_make_root(root_inode);
if (!sb->s_root) {
fat_msg(sb, KERN_ERR, "get root inode failed");
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index b0e12bf..c27c630 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -440,7 +440,7 @@
struct inode *old_inode, *new_inode;
struct fat_slot_info old_sinfo, sinfo;
struct timespec ts;
- loff_t dotdot_i_pos, new_i_pos;
+ loff_t new_i_pos;
int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
@@ -456,8 +456,7 @@
is_dir = S_ISDIR(old_inode->i_mode);
update_dotdot = (is_dir && old_dir != new_dir);
if (update_dotdot) {
- if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de,
- &dotdot_i_pos) < 0) {
+ if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
err = -EIO;
goto out;
}
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 6a6d8c0..e535dd7 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -914,7 +914,7 @@
struct inode *old_inode, *new_inode;
struct fat_slot_info old_sinfo, sinfo;
struct timespec ts;
- loff_t dotdot_i_pos, new_i_pos;
+ loff_t new_i_pos;
int err, is_dir, update_dotdot, corrupt = 0;
struct super_block *sb = old_dir->i_sb;
@@ -929,8 +929,7 @@
is_dir = S_ISDIR(old_inode->i_mode);
update_dotdot = (is_dir && old_dir != new_dir);
if (update_dotdot) {
- if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de,
- &dotdot_i_pos) < 0) {
+ if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
err = -EIO;
goto out;
}
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);
}