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linux/fs/dcache.c

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/*
* fs/dcache.c
*
* Complete reimplementation
* (C) 1997 Thomas Schoebel-Theuer,
* with heavy changes by Linus Torvalds
*/
/*
* Notes on the allocation strategy:
*
* The dcache is a master of the icache - whenever a dcache entry
* exists, the inode will always exist. "iput()" is done either when
* the dcache entry is deleted or garbage collected.
*/
#include <linux/syscalls.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <asm/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/swap.h>
#include <linux/bootmem.h>
#include "internal.h"
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
static __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
EXPORT_SYMBOL(dcache_lock);
static struct kmem_cache *dentry_cache __read_mostly;
#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
/*
* This is the single most critical data structure when it comes
* to the dcache: the hashtable for lookups. Somebody should try
* to make this good - I've just made it work.
*
* This hash-function tries to avoid losing too many bits of hash
* information, yet avoid using a prime hash-size or similar.
*/
#define D_HASHBITS d_hash_shift
#define D_HASHMASK d_hash_mask
static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
static struct hlist_head *dentry_hashtable __read_mostly;
static LIST_HEAD(dentry_unused);
/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};
static void __d_free(struct dentry *dentry)
{
if (dname_external(dentry))
kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry);
}
static void d_callback(struct rcu_head *head)
{
struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
__d_free(dentry);
}
/*
* no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
* inside dcache_lock.
*/
static void d_free(struct dentry *dentry)
{
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
/* if dentry was never inserted into hash, immediate free is OK */
if (dentry->d_hash.pprev == NULL)
__d_free(dentry);
else
call_rcu(&dentry->d_u.d_rcu, d_callback);
}
/*
* Release the dentry's inode, using the filesystem
* d_iput() operation if defined.
* Called with dcache_lock and per dentry lock held, drops both.
*/
static void dentry_iput(struct dentry * dentry)
{
struct inode *inode = dentry->d_inode;
if (inode) {
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
if (!inode->i_nlink)
fsnotify_inoderemove(inode);
if (dentry->d_op && dentry->d_op->d_iput)
dentry->d_op->d_iput(dentry, inode);
else
iput(inode);
} else {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
}
/**
* d_kill - kill dentry and return parent
* @dentry: dentry to kill
*
* Called with dcache_lock and d_lock, releases both. The dentry must
* already be unhashed and removed from the LRU.
*
* If this is the root of the dentry tree, return NULL.
*/
static struct dentry *d_kill(struct dentry *dentry)
{
struct dentry *parent;
list_del(&dentry->d_u.d_child);
dentry_stat.nr_dentry--; /* For d_free, below */
/*drops the locks, at that point nobody can reach this dentry */
dentry_iput(dentry);
parent = dentry->d_parent;
d_free(dentry);
return dentry == parent ? NULL : parent;
}
/*
* This is dput
*
* This is complicated by the fact that we do not want to put
* dentries that are no longer on any hash chain on the unused
* list: we'd much rather just get rid of them immediately.
*
* However, that implies that we have to traverse the dentry
* tree upwards to the parents which might _also_ now be
* scheduled for deletion (it may have been only waiting for
* its last child to go away).
*
* This tail recursion is done by hand as we don't want to depend
* on the compiler to always get this right (gcc generally doesn't).
* Real recursion would eat up our stack space.
*/
/*
* dput - release a dentry
* @dentry: dentry to release
*
* Release a dentry. This will drop the usage count and if appropriate
* call the dentry unlink method as well as removing it from the queues and
* releasing its resources. If the parent dentries were scheduled for release
* they too may now get deleted.
*
* no dcache lock, please.
*/
void dput(struct dentry *dentry)
{
if (!dentry)
return;
repeat:
if (atomic_read(&dentry->d_count) == 1)
might_sleep();
if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
return;
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count)) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return;
}
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
if (dentry->d_op && dentry->d_op->d_delete) {
if (dentry->d_op->d_delete(dentry))
goto unhash_it;
}
/* Unreachable? Get rid of it */
if (d_unhashed(dentry))
goto kill_it;
if (list_empty(&dentry->d_lru)) {
dentry->d_flags |= DCACHE_REFERENCED;
list_add(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
}
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return;
unhash_it:
__d_drop(dentry);
kill_it:
/* If dentry was on d_lru list
* delete it from there
*/
if (!list_empty(&dentry->d_lru)) {
list_del(&dentry->d_lru);
dentry_stat.nr_unused--;
}
dentry = d_kill(dentry);
if (dentry)
goto repeat;
}
/**
* d_invalidate - invalidate a dentry
* @dentry: dentry to invalidate
*
* Try to invalidate the dentry if it turns out to be
* possible. If there are other dentries that can be
* reached through this one we can't delete it and we
* return -EBUSY. On success we return 0.
*
* no dcache lock.
*/
int d_invalidate(struct dentry * dentry)
{
/*
* If it's already been dropped, return OK.
*/
spin_lock(&dcache_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dcache_lock);
return 0;
}
/*
* Check whether to do a partial shrink_dcache
* to get rid of unused child entries.
*/
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&dcache_lock);
shrink_dcache_parent(dentry);
spin_lock(&dcache_lock);
}
/*
* Somebody else still using it?
*
* If it's a directory, we can't drop it
* for fear of somebody re-populating it
* with children (even though dropping it
* would make it unreachable from the root,
* we might still populate it if it was a
* working directory or similar).
*/
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) > 1) {
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return -EBUSY;
}
}
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return 0;
}
/* This should be called _only_ with dcache_lock held */
static inline struct dentry * __dget_locked(struct dentry *dentry)
{
atomic_inc(&dentry->d_count);
if (!list_empty(&dentry->d_lru)) {
dentry_stat.nr_unused--;
list_del_init(&dentry->d_lru);
}
return dentry;
}
struct dentry * dget_locked(struct dentry *dentry)
{
return __dget_locked(dentry);
}
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
* @want_discon: flag, used by d_splice_alias, to request
* that only a DISCONNECTED alias be returned.
*
* If inode has a hashed alias, or is a directory and has any alias,
* acquire the reference to alias and return it. Otherwise return NULL.
* Notice that if inode is a directory there can be only one alias and
* it can be unhashed only if it has no children, or if it is the root
* of a filesystem.
*
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
* any other hashed alias over that one unless @want_discon is set,
* in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
*/
static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
{
struct list_head *head, *next, *tmp;
struct dentry *alias, *discon_alias=NULL;
head = &inode->i_dentry;
next = inode->i_dentry.next;
while (next != head) {
tmp = next;
next = tmp->next;
prefetch(next);
alias = list_entry(tmp, struct dentry, d_alias);
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
if (IS_ROOT(alias) &&
(alias->d_flags & DCACHE_DISCONNECTED))
discon_alias = alias;
else if (!want_discon) {
__dget_locked(alias);
return alias;
}
}
}
if (discon_alias)
__dget_locked(discon_alias);
return discon_alias;
}
struct dentry * d_find_alias(struct inode *inode)
{
struct dentry *de = NULL;
if (!list_empty(&inode->i_dentry)) {
spin_lock(&dcache_lock);
de = __d_find_alias(inode, 0);
spin_unlock(&dcache_lock);
}
return de;
}
/*
* Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.
*/
void d_prune_aliases(struct inode *inode)
{
struct dentry *dentry;
restart:
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!atomic_read(&dentry->d_count)) {
__dget_locked(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(dentry);
goto restart;
}
spin_unlock(&dentry->d_lock);
}
spin_unlock(&dcache_lock);
}
/*
* Throw away a dentry - free the inode, dput the parent. This requires that
* the LRU list has already been removed.
*
* If prune_parents is true, try to prune ancestors as well.
*
* Called with dcache_lock, drops it and then regains.
* Called with dentry->d_lock held, drops it.
*/
static void prune_one_dentry(struct dentry * dentry, int prune_parents)
{
__d_drop(dentry);
dentry = d_kill(dentry);
if (!prune_parents) {
dput(dentry);
spin_lock(&dcache_lock);
return;
}
/*
* Prune ancestors. Locking is simpler than in dput(),
* because dcache_lock needs to be taken anyway.
*/
spin_lock(&dcache_lock);
while (dentry) {
if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
return;
if (dentry->d_op && dentry->d_op->d_delete)
dentry->d_op->d_delete(dentry);
if (!list_empty(&dentry->d_lru)) {
list_del(&dentry->d_lru);
dentry_stat.nr_unused--;
}
__d_drop(dentry);
dentry = d_kill(dentry);
spin_lock(&dcache_lock);
}
}
/**
* prune_dcache - shrink the dcache
* @count: number of entries to try and free
* @sb: if given, ignore dentries for other superblocks
* which are being unmounted.
* @prune_parents: if true, try to prune ancestors as well in one go
*
* Shrink the dcache. This is done when we need
* more memory, or simply when we need to unmount
* something (at which point we need to unuse
* all dentries).
*
* This function may fail to free any resources if
* all the dentries are in use.
*/
static void prune_dcache(int count, struct super_block *sb, int prune_parents)
{
spin_lock(&dcache_lock);
for (; count ; count--) {
struct dentry *dentry;
struct list_head *tmp;
struct rw_semaphore *s_umount;
cond_resched_lock(&dcache_lock);
tmp = dentry_unused.prev;
if (sb) {
/* Try to find a dentry for this sb, but don't try
* too hard, if they aren't near the tail they will
* be moved down again soon
*/
int skip = count;
while (skip && tmp != &dentry_unused &&
list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
skip--;
tmp = tmp->prev;
}
}
if (tmp == &dentry_unused)
break;
list_del_init(tmp);
prefetch(dentry_unused.prev);
dentry_stat.nr_unused--;
dentry = list_entry(tmp, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
/*
* We found an inuse dentry which was not removed from
* dentry_unused because of laziness during lookup. Do not free
* it - just keep it off the dentry_unused list.
*/
if (atomic_read(&dentry->d_count)) {
spin_unlock(&dentry->d_lock);
continue;
}
/* If the dentry was recently referenced, don't free it. */
if (dentry->d_flags & DCACHE_REFERENCED) {
dentry->d_flags &= ~DCACHE_REFERENCED;
list_add(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
spin_unlock(&dentry->d_lock);
continue;
}
/*
* If the dentry is not DCACHED_REFERENCED, it is time
* to remove it from the dcache, provided the super block is
* NULL (which means we are trying to reclaim memory)
* or this dentry belongs to the same super block that
* we want to shrink.
*/
/*
* If this dentry is for "my" filesystem, then I can prune it
* without taking the s_umount lock (I already hold it).
*/
if (sb && dentry->d_sb == sb) {
prune_one_dentry(dentry, prune_parents);
continue;
}
/*
* ...otherwise we need to be sure this filesystem isn't being
* unmounted, otherwise we could race with
* generic_shutdown_super(), and end up holding a reference to
* an inode while the filesystem is unmounted.
* So we try to get s_umount, and make sure s_root isn't NULL.
* (Take a local copy of s_umount to avoid a use-after-free of
* `dentry').
*/
s_umount = &dentry->d_sb->s_umount;
if (down_read_trylock(s_umount)) {
if (dentry->d_sb->s_root != NULL) {
prune_one_dentry(dentry, prune_parents);
up_read(s_umount);
continue;
}
up_read(s_umount);
}
spin_unlock(&dentry->d_lock);
/*
* Insert dentry at the head of the list as inserting at the
* tail leads to a cycle.
*/
list_add(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
}
spin_unlock(&dcache_lock);
}
/*
* Shrink the dcache for the specified super block.
* This allows us to unmount a device without disturbing
* the dcache for the other devices.
*
* This implementation makes just two traversals of the
* unused list. On the first pass we move the selected
* dentries to the most recent end, and on the second
* pass we free them. The second pass must restart after
* each dput(), but since the target dentries are all at
* the end, it's really just a single traversal.
*/
/**
* shrink_dcache_sb - shrink dcache for a superblock
* @sb: superblock
*
* Shrink the dcache for the specified super block. This
* is used to free the dcache before unmounting a file
* system
*/
void shrink_dcache_sb(struct super_block * sb)
{
struct list_head *tmp, *next;
struct dentry *dentry;
/*
* Pass one ... move the dentries for the specified
* superblock to the most recent end of the unused list.
*/
spin_lock(&dcache_lock);
list_for_each_safe(tmp, next, &dentry_unused) {
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
list_move(tmp, &dentry_unused);
}
/*
* Pass two ... free the dentries for this superblock.
*/
repeat:
list_for_each_safe(tmp, next, &dentry_unused) {
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
dentry_stat.nr_unused--;
list_del_init(tmp);
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count)) {
spin_unlock(&dentry->d_lock);
continue;
}
prune_one_dentry(dentry, 1);
cond_resched_lock(&dcache_lock);
goto repeat;
}
spin_unlock(&dcache_lock);
}
/*
* destroy a single subtree of dentries for unmount
* - see the comments on shrink_dcache_for_umount() for a description of the
* locking
*/
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
{
struct dentry *parent;
unsigned detached = 0;
BUG_ON(!IS_ROOT(dentry));
/* detach this root from the system */
spin_lock(&dcache_lock);
if (!list_empty(&dentry->d_lru)) {
dentry_stat.nr_unused--;
list_del_init(&dentry->d_lru);
}
__d_drop(dentry);
spin_unlock(&dcache_lock);
for (;;) {
/* descend to the first leaf in the current subtree */
while (!list_empty(&dentry->d_subdirs)) {
struct dentry *loop;
/* this is a branch with children - detach all of them
* from the system in one go */
spin_lock(&dcache_lock);
list_for_each_entry(loop, &dentry->d_subdirs,
d_u.d_child) {
if (!list_empty(&loop->d_lru)) {
dentry_stat.nr_unused--;
list_del_init(&loop->d_lru);
}
__d_drop(loop);
cond_resched_lock(&dcache_lock);
}
spin_unlock(&dcache_lock);
/* move to the first child */
dentry = list_entry(dentry->d_subdirs.next,
struct dentry, d_u.d_child);
}
/* consume the dentries from this leaf up through its parents
* until we find one with children or run out altogether */
do {
struct inode *inode;
if (atomic_read(&dentry->d_count) != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
" still in use (%d)"
" [unmount of %s %s]\n",
dentry,
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry->d_name.name,
atomic_read(&dentry->d_count),
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
BUG();
}
parent = dentry->d_parent;
if (parent == dentry)
parent = NULL;
else
atomic_dec(&parent->d_count);
list_del(&dentry->d_u.d_child);
detached++;
inode = dentry->d_inode;
if (inode) {
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
if (dentry->d_op && dentry->d_op->d_iput)
dentry->d_op->d_iput(dentry, inode);
else
iput(inode);
}
d_free(dentry);
/* finished when we fall off the top of the tree,
* otherwise we ascend to the parent and move to the
* next sibling if there is one */
if (!parent)
goto out;
dentry = parent;
} while (list_empty(&dentry->d_subdirs));
dentry = list_entry(dentry->d_subdirs.next,
struct dentry, d_u.d_child);
}
out:
/* several dentries were freed, need to correct nr_dentry */
spin_lock(&dcache_lock);
dentry_stat.nr_dentry -= detached;
spin_unlock(&dcache_lock);
}
/*
* destroy the dentries attached to a superblock on unmounting
* - we don't need to use dentry->d_lock, and only need dcache_lock when
* removing the dentry from the system lists and hashes because:
* - the superblock is detached from all mountings and open files, so the
* dentry trees will not be rearranged by the VFS
* - s_umount is write-locked, so the memory pressure shrinker will ignore
* any dentries belonging to this superblock that it comes across
* - the filesystem itself is no longer permitted to rearrange the dentries
* in this superblock
*/
void shrink_dcache_for_umount(struct super_block *sb)
{
struct dentry *dentry;
if (down_read_trylock(&sb->s_umount))
BUG();
dentry = sb->s_root;
sb->s_root = NULL;
atomic_dec(&dentry->d_count);
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_empty(&sb->s_anon)) {
dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
shrink_dcache_for_umount_subtree(dentry);
}
}
/*
* Search for at least 1 mount point in the dentry's subdirs.
* We descend to the next level whenever the d_subdirs
* list is non-empty and continue searching.
*/
/**
* have_submounts - check for mounts over a dentry
* @parent: dentry to check.
*
* Return true if the parent or its subdirectories contain
* a mount point
*/
int have_submounts(struct dentry *parent)
{
struct dentry *this_parent = parent;
struct list_head *next;
spin_lock(&dcache_lock);
if (d_mountpoint(parent))
goto positive;
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
/* Have we found a mount point ? */
if (d_mountpoint(dentry))
goto positive;
if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
goto repeat;
}
}
/*
* All done at this level ... ascend and resume the search.
*/
if (this_parent != parent) {
next = this_parent->d_u.d_child.next;
this_parent = this_parent->d_parent;
goto resume;
}
spin_unlock(&dcache_lock);
return 0; /* No mount points found in tree */
positive:
spin_unlock(&dcache_lock);
return 1;
}
/*
* Search the dentry child list for the specified parent,
* and move any unused dentries to the end of the unused
* list for prune_dcache(). We descend to the next level
* whenever the d_subdirs list is non-empty and continue
* searching.
*
* It returns zero iff there are no unused children,
* otherwise it returns the number of children moved to
* the end of the unused list. This may not be the total
* number of unused children, because select_parent can
* drop the lock and return early due to latency
* constraints.
*/
static int select_parent(struct dentry * parent)
{
struct dentry *this_parent = parent;
struct list_head *next;
int found = 0;
spin_lock(&dcache_lock);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
if (!list_empty(&dentry->d_lru)) {
dentry_stat.nr_unused--;
list_del_init(&dentry->d_lru);
}
/*
* move only zero ref count dentries to the end
* of the unused list for prune_dcache
*/
if (!atomic_read(&dentry->d_count)) {
list_add_tail(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
found++;
}
/*
* We can return to the caller if we have found some (this
* ensures forward progress). We'll be coming back to find
* the rest.
*/
if (found && need_resched())
goto out;
/*
* Descend a level if the d_subdirs list is non-empty.
*/
if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
goto repeat;
}
}
/*
* All done at this level ... ascend and resume the search.
*/
if (this_parent != parent) {
next = this_parent->d_u.d_child.next;
this_parent = this_parent->d_parent;
goto resume;
}
out:
spin_unlock(&dcache_lock);
return found;
}
/**
* shrink_dcache_parent - prune dcache
* @parent: parent of entries to prune
*
* Prune the dcache to remove unused children of the parent dentry.
*/
void shrink_dcache_parent(struct dentry * parent)
{
int found;
while ((found = select_parent(parent)) != 0)
prune_dcache(found, parent->d_sb, 1);
}
/*
* Scan `nr' dentries and return the number which remain.
*
* We need to avoid reentering the filesystem if the caller is performing a
* GFP_NOFS allocation attempt. One example deadlock is:
*
* ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
* prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
* ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
*
* In this case we return -1 to tell the caller that we baled.
*/
static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
{
if (nr) {
if (!(gfp_mask & __GFP_FS))
return -1;
prune_dcache(nr, NULL, 1);
}
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
static struct shrinker dcache_shrinker = {
.shrink = shrink_dcache_memory,
.seeks = DEFAULT_SEEKS,
};
/**
* d_alloc - allocate a dcache entry
* @parent: parent of entry to allocate
* @name: qstr of the name
*
* Allocates a dentry. It returns %NULL if there is insufficient memory
* available. On a success the dentry is returned. The name passed in is
* copied and the copy passed in may be reused after this call.
*/
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
{
struct dentry *dentry;
char *dname;
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
if (!dentry)
return NULL;
if (name->len > DNAME_INLINE_LEN-1) {
dname = kmalloc(name->len + 1, GFP_KERNEL);
if (!dname) {
kmem_cache_free(dentry_cache, dentry);
return NULL;
}
} else {
dname = dentry->d_iname;
}
dentry->d_name.name = dname;
dentry->d_name.len = name->len;
dentry->d_name.hash = name->hash;
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
atomic_set(&dentry->d_count, 1);
dentry->d_flags = DCACHE_UNHASHED;
spin_lock_init(&dentry->d_lock);
dentry->d_inode = NULL;
dentry->d_parent = NULL;
dentry->d_sb = NULL;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
dentry->d_mounted = 0;
#ifdef CONFIG_PROFILING
dentry->d_cookie = NULL;
#endif
INIT_HLIST_NODE(&dentry->d_hash);
INIT_LIST_HEAD(&dentry->d_lru);
INIT_LIST_HEAD(&dentry->d_subdirs);
INIT_LIST_HEAD(&dentry->d_alias);
if (parent) {
dentry->d_parent = dget(parent);
dentry->d_sb = parent->d_sb;
} else {
INIT_LIST_HEAD(&dentry->d_u.d_child);
}
spin_lock(&dcache_lock);
if (parent)
list_add(&dentry->d_u.d_child, &parent->d_subdirs);
dentry_stat.nr_dentry++;
spin_unlock(&dcache_lock);
return dentry;
}
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
{
struct qstr q;
q.name = name;
q.len = strlen(name);
q.hash = full_name_hash(q.name, q.len);
return d_alloc(parent, &q);
}
/**
* d_instantiate - fill in inode information for a dentry
* @entry: dentry to complete
* @inode: inode to attach to this dentry
*
* Fill in inode information in the entry.
*
* This turns negative dentries into productive full members
* of society.
*
* NOTE! This assumes that the inode count has been incremented
* (or otherwise set) by the caller to indicate that it is now
* in use by the dcache.
*/
void d_instantiate(struct dentry *entry, struct inode * inode)
{
BUG_ON(!list_empty(&entry->d_alias));
spin_lock(&dcache_lock);
if (inode)
list_add(&entry->d_alias, &inode->i_dentry);
entry->d_inode = inode;
fsnotify_d_instantiate(entry, inode);
spin_unlock(&dcache_lock);
security_d_instantiate(entry, inode);
}
/**
* d_instantiate_unique - instantiate a non-aliased dentry
* @entry: dentry to instantiate
* @inode: inode to attach to this dentry
*
* Fill in inode information in the entry. On success, it returns NULL.
* If an unhashed alias of "entry" already exists, then we return the
* aliased dentry instead and drop one reference to inode.
*
* Note that in order to avoid conflicts with rename() etc, the caller
* had better be holding the parent directory semaphore.
*
* This also assumes that the inode count has been incremented
* (or otherwise set) by the caller to indicate that it is now
* in use by the dcache.
*/
static struct dentry *__d_instantiate_unique(struct dentry *entry,
struct inode *inode)
{
struct dentry *alias;
int len = entry->d_name.len;
const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash;
if (!inode) {
entry->d_inode = NULL;
return NULL;
}
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct qstr *qstr = &alias->d_name;
if (qstr->hash != hash)
continue;
if (alias->d_parent != entry->d_parent)
continue;
if (qstr->len != len)
continue;
if (memcmp(qstr->name, name, len))
continue;
dget_locked(alias);
return alias;
}
list_add(&entry->d_alias, &inode->i_dentry);
entry->d_inode = inode;
fsnotify_d_instantiate(entry, inode);
return NULL;
}
struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
{
struct dentry *result;
BUG_ON(!list_empty(&entry->d_alias));
spin_lock(&dcache_lock);
result = __d_instantiate_unique(entry, inode);
spin_unlock(&dcache_lock);
if (!result) {
security_d_instantiate(entry, inode);
return NULL;
}
BUG_ON(!d_unhashed(result));
iput(inode);
return result;
}
EXPORT_SYMBOL(d_instantiate_unique);
/**
* d_alloc_root - allocate root dentry
* @root_inode: inode to allocate the root for
*
* Allocate a root ("/") dentry for the inode given. The inode is
* instantiated and returned. %NULL is returned if there is insufficient
* memory or the inode passed is %NULL.
*/
struct dentry * d_alloc_root(struct inode * root_inode)
{
struct dentry *res = NULL;
if (root_inode) {
static const struct qstr name = { .name = "/", .len = 1 };
res = d_alloc(NULL, &name);
if (res) {
res->d_sb = root_inode->i_sb;
res->d_parent = res;
d_instantiate(res, root_inode);
}
}
return res;
}
static inline struct hlist_head *d_hash(struct dentry *parent,
unsigned long hash)
{
hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
return dentry_hashtable + (hash & D_HASHMASK);
}
/**
* d_alloc_anon - allocate an anonymous dentry
* @inode: inode to allocate the dentry for
*
* This is similar to d_alloc_root. It is used by filesystems when
* creating a dentry for a given inode, often in the process of
* mapping a filehandle to a dentry. The returned dentry may be
* anonymous, or may have a full name (if the inode was already
* in the cache). The file system may need to make further
* efforts to connect this dentry into the dcache properly.
*
* When called on a directory inode, we must ensure that
* the inode only ever has one dentry. If a dentry is
* found, that is returned instead of allocating a new one.
*
* On successful return, the reference to the inode has been transferred
* to the dentry. If %NULL is returned (indicating kmalloc failure),
* the reference on the inode has not been released.
*/
struct dentry * d_alloc_anon(struct inode *inode)
{
static const struct qstr anonstring = { .name = "" };
struct dentry *tmp;
struct dentry *res;
if ((res = d_find_alias(inode))) {
iput(inode);
return res;
}
tmp = d_alloc(NULL, &anonstring);
if (!tmp)
return NULL;
tmp->d_parent = tmp; /* make sure dput doesn't croak */
spin_lock(&dcache_lock);
res = __d_find_alias(inode, 0);
if (!res) {
/* attach a disconnected dentry */
res = tmp;
tmp = NULL;
spin_lock(&res->d_lock);
res->d_sb = inode->i_sb;
res->d_parent = res;
res->d_inode = inode;
res->d_flags |= DCACHE_DISCONNECTED;
res->d_flags &= ~DCACHE_UNHASHED;
list_add(&res->d_alias, &inode->i_dentry);
hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
spin_unlock(&res->d_lock);
inode = NULL; /* don't drop reference */
}
spin_unlock(&dcache_lock);
if (inode)
iput(inode);
if (tmp)
dput(tmp);
return res;
}
/**
* d_splice_alias - splice a disconnected dentry into the tree if one exists
* @inode: the inode which may have a disconnected dentry
* @dentry: a negative dentry which we want to point to the inode.
*
* If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
* DCACHE_DISCONNECTED), then d_move that in place of the given dentry
* and return it, else simply d_add the inode to the dentry and return NULL.
*
* This is needed in the lookup routine of any filesystem that is exportable
* (via knfsd) so that we can build dcache paths to directories effectively.
*
* If a dentry was found and moved, then it is returned. Otherwise NULL
* is returned. This matches the expected return value of ->lookup.
*
*/
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
struct dentry *new = NULL;
if (inode && S_ISDIR(inode->i_mode)) {
spin_lock(&dcache_lock);
new = __d_find_alias(inode, 1);
if (new) {
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
fsnotify_d_instantiate(new, inode);
spin_unlock(&dcache_lock);
security_d_instantiate(new, inode);
d_rehash(dentry);
d_move(new, dentry);
iput(inode);
} else {
/* d_instantiate takes dcache_lock, so we do it by hand */
list_add(&dentry->d_alias, &inode->i_dentry);
dentry->d_inode = inode;
fsnotify_d_instantiate(dentry, inode);
spin_unlock(&dcache_lock);
security_d_instantiate(dentry, inode);
d_rehash(dentry);
}
} else
d_add(dentry, inode);
return new;
}
/**
* d_lookup - search for a dentry
* @parent: parent dentry
* @name: qstr of name we wish to find
*
* Searches the children of the parent dentry for the name in question. If
* the dentry is found its reference count is incremented and the dentry
* is returned. The caller must use d_put to free the entry when it has
* finished using it. %NULL is returned on failure.
*
* __d_lookup is dcache_lock free. The hash list is protected using RCU.
* Memory barriers are used while updating and doing lockless traversal.
* To avoid races with d_move while rename is happening, d_lock is used.
*
* Overflows in memcmp(), while d_move, are avoided by keeping the length
* and name pointer in one structure pointed by d_qstr.
*
* rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
* lookup is going on.
*
* dentry_unused list is not updated even if lookup finds the required dentry
* in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
* select_parent and __dget_locked. This laziness saves lookup from dcache_lock
* acquisition.
*
* d_lookup() is protected against the concurrent renames in some unrelated
* directory using the seqlockt_t rename_lock.
*/
struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
{
struct dentry * dentry = NULL;
unsigned long seq;
do {
seq = read_seqbegin(&rename_lock);
dentry = __d_lookup(parent, name);
if (dentry)
break;
} while (read_seqretry(&rename_lock, seq));
return dentry;
}
struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
{
unsigned int len = name->len;
unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct hlist_head *head = d_hash(parent,hash);
struct dentry *found = NULL;
struct hlist_node *node;
struct dentry *dentry;
rcu_read_lock();
hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
struct qstr *qstr;
if (dentry->d_name.hash != hash)
continue;
if (dentry->d_parent != parent)
continue;
spin_lock(&dentry->d_lock);
/*
* Recheck the dentry after taking the lock - d_move may have
* changed things. Don't bother checking the hash because we're
* about to compare the whole name anyway.
*/
if (dentry->d_parent != parent)
goto next;
/*
* It is safe to compare names since d_move() cannot
* change the qstr (protected by d_lock).
*/
qstr = &dentry->d_name;
if (parent->d_op && parent->d_op->d_compare) {
if (parent->d_op->d_compare(parent, qstr, name))
goto next;
} else {
if (qstr->len != len)
goto next;
if (memcmp(qstr->name, str, len))
goto next;
}
if (!d_unhashed(dentry)) {
atomic_inc(&dentry->d_count);
found = dentry;
}
spin_unlock(&dentry->d_lock);
break;
next:
spin_unlock(&dentry->d_lock);
}
rcu_read_unlock();
return found;
}
/**
* d_hash_and_lookup - hash the qstr then search for a dentry
* @dir: Directory to search in
* @name: qstr of name we wish to find
*
* On hash failure or on lookup failure NULL is returned.
*/
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
struct dentry *dentry = NULL;
/*
* Check for a fs-specific hash function. Note that we must
* calculate the standard hash first, as the d_op->d_hash()
* routine may choose to leave the hash value unchanged.
*/
name->hash = full_name_hash(name->name, name->len);
if (dir->d_op && dir->d_op->d_hash) {
if (dir->d_op->d_hash(dir, name) < 0)
goto out;
}
dentry = d_lookup(dir, name);
out:
return dentry;
}
/**
* d_validate - verify dentry provided from insecure source
* @dentry: The dentry alleged to be valid child of @dparent
* @dparent: The parent dentry (known to be valid)
* @hash: Hash of the dentry
* @len: Length of the name
*
* An insecure source has sent us a dentry, here we verify it and dget() it.
* This is used by ncpfs in its readdir implementation.
* Zero is returned in the dentry is invalid.
*/
int d_validate(struct dentry *dentry, struct dentry *dparent)
{
struct hlist_head *base;
struct hlist_node *lhp;
/* Check whether the ptr might be valid at all.. */
if (!kmem_ptr_validate(dentry_cache, dentry))
goto out;
if (dentry->d_parent != dparent)
goto out;
spin_lock(&dcache_lock);
base = d_hash(dparent, dentry->d_name.hash);
hlist_for_each(lhp,base) {
/* hlist_for_each_entry_rcu() not required for d_hash list
* as it is parsed under dcache_lock
*/
if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
__dget_locked(dentry);
spin_unlock(&dcache_lock);
return 1;
}
}
spin_unlock(&dcache_lock);
out:
return 0;
}
/*
* When a file is deleted, we have two options:
* - turn this dentry into a negative dentry
* - unhash this dentry and free it.
*
* Usually, we want to just turn this into
* a negative dentry, but if anybody else is
* currently using the dentry or the inode
* we can't do that and we fall back on removing
* it from the hash queues and waiting for
* it to be deleted later when it has no users
*/
/**
* d_delete - delete a dentry
* @dentry: The dentry to delete
*
* Turn the dentry into a negative dentry if possible, otherwise
* remove it from the hash queues so it can be deleted later
*/
void d_delete(struct dentry * dentry)
{
int isdir = 0;
/*
* Are we the only user?
*/
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (atomic_read(&dentry->d_count) == 1) {
dentry_iput(dentry);
fsnotify_nameremove(dentry, isdir);
/* remove this and other inotify debug checks after 2.6.18 */
dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
return;
}
if (!d_unhashed(dentry))
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
fsnotify_nameremove(dentry, isdir);
}
static void __d_rehash(struct dentry * entry, struct hlist_head *list)
{
entry->d_flags &= ~DCACHE_UNHASHED;
hlist_add_head_rcu(&entry->d_hash, list);
}
static void _d_rehash(struct dentry * entry)
{
__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
}
/**
* d_rehash - add an entry back to the hash
* @entry: dentry to add to the hash
*
* Adds a dentry to the hash according to its name.
*/
void d_rehash(struct dentry * entry)
{
spin_lock(&dcache_lock);
spin_lock(&entry->d_lock);
_d_rehash(entry);
spin_unlock(&entry->d_lock);
spin_unlock(&dcache_lock);
}
#define do_switch(x,y) do { \
__typeof__ (x) __tmp = x; \
x = y; y = __tmp; } while (0)
/*
* When switching names, the actual string doesn't strictly have to
* be preserved in the target - because we're dropping the target
* anyway. As such, we can just do a simple memcpy() to copy over
* the new name before we switch.
*
* Note that we have to be a lot more careful about getting the hash
* switched - we have to switch the hash value properly even if it
* then no longer matches the actual (corrupted) string of the target.
* The hash value has to match the hash queue that the dentry is on..
*/
static void switch_names(struct dentry *dentry, struct dentry *target)
{
if (dname_external(target)) {
if (dname_external(dentry)) {
/*
* Both external: swap the pointers
*/
do_switch(target->d_name.name, dentry->d_name.name);
} else {
/*
* dentry:internal, target:external. Steal target's
* storage and make target internal.
*/
dentry->d_name.name = target->d_name.name;
target->d_name.name = target->d_iname;
}
} else {
if (dname_external(dentry)) {
/*
* dentry:external, target:internal. Give dentry's
* storage to target and make dentry internal
*/
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
target->d_name.name = dentry->d_name.name;
dentry->d_name.name = dentry->d_iname;
} else {
/*
* Both are internal. Just copy target to dentry
*/
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
}
}
}
/*
* We cannibalize "target" when moving dentry on top of it,
* because it's going to be thrown away anyway. We could be more
* polite about it, though.
*
* This forceful removal will result in ugly /proc output if
* somebody holds a file open that got deleted due to a rename.
* We could be nicer about the deleted file, and let it show
* up under the name it got deleted rather than the name that
* deleted it.
*/
/*
* d_move_locked - move a dentry
* @dentry: entry to move
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way.
*/
static void d_move_locked(struct dentry * dentry, struct dentry * target)
{
struct hlist_head *list;
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
write_seqlock(&rename_lock);
/*
* XXXX: do we really need to take target->d_lock?
*/
if (target < dentry) {
spin_lock(&target->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
} else {
spin_lock(&dentry->d_lock);
spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
}
/* Move the dentry to the target hash queue, if on different bucket */
if (dentry->d_flags & DCACHE_UNHASHED)
goto already_unhashed;
hlist_del_rcu(&dentry->d_hash);
already_unhashed:
list = d_hash(target->d_parent, target->d_name.hash);
__d_rehash(dentry, list);
/* Unhash the target: dput() will then get rid of it */
__d_drop(target);
list_del(&dentry->d_u.d_child);
list_del(&target->d_u.d_child);
/* Switch the names.. */
switch_names(dentry, target);
do_switch(dentry->d_name.len, target->d_name.len);
do_switch(dentry->d_name.hash, target->d_name.hash);
/* ... and switch the parents */
if (IS_ROOT(dentry)) {
dentry->d_parent = target->d_parent;
target->d_parent = target;
INIT_LIST_HEAD(&target->d_u.d_child);
} else {
do_switch(dentry->d_parent, target->d_parent);
/* And add them back to the (new) parent lists */
list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
}
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
spin_unlock(&target->d_lock);
fsnotify_d_move(dentry);
spin_unlock(&dentry->d_lock);
write_sequnlock(&rename_lock);
}
/**
* d_move - move a dentry
* @dentry: entry to move
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way.
*/
void d_move(struct dentry * dentry, struct dentry * target)
{
spin_lock(&dcache_lock);
d_move_locked(dentry, target);
spin_unlock(&dcache_lock);
}
/*
* Helper that returns 1 if p1 is a parent of p2, else 0
*/
static int d_isparent(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
for (p = p2; p->d_parent != p; p = p->d_parent) {
if (p->d_parent == p1)
return 1;
}
return 0;
}
/*
* This helper attempts to cope with remotely renamed directories
*
* It assumes that the caller is already holding
* dentry->d_parent->d_inode->i_mutex and the dcache_lock
*
* Note: If ever the locking in lock_rename() changes, then please
* remember to update this too...
*
* On return, dcache_lock will have been unlocked.
*/
static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
{
struct mutex *m1 = NULL, *m2 = NULL;
struct dentry *ret;
/* If alias and dentry share a parent, then no extra locks required */
if (alias->d_parent == dentry->d_parent)
goto out_unalias;
/* Check for loops */
ret = ERR_PTR(-ELOOP);
if (d_isparent(alias, dentry))
goto out_err;
/* See lock_rename() */
ret = ERR_PTR(-EBUSY);
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
goto out_err;
m1 = &dentry->d_sb->s_vfs_rename_mutex;
if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
goto out_err;
m2 = &alias->d_parent->d_inode->i_mutex;
out_unalias:
d_move_locked(alias, dentry);
ret = alias;
out_err:
spin_unlock(&dcache_lock);
if (m2)
mutex_unlock(m2);
if (m1)
mutex_unlock(m1);
return ret;
}
/*
* Prepare an anonymous dentry for life in the superblock's dentry tree as a
* named dentry in place of the dentry to be replaced.
*/
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
struct dentry *dparent, *aparent;
switch_names(dentry, anon);
do_switch(dentry->d_name.len, anon->d_name.len);
do_switch(dentry->d_name.hash, anon->d_name.hash);
dparent = dentry->d_parent;
aparent = anon->d_parent;
dentry->d_parent = (aparent == anon) ? dentry : aparent;
list_del(&dentry->d_u.d_child);
if (!IS_ROOT(dentry))
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
else
INIT_LIST_HEAD(&dentry->d_u.d_child);
anon->d_parent = (dparent == dentry) ? anon : dparent;
list_del(&anon->d_u.d_child);
if (!IS_ROOT(anon))
list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
else
INIT_LIST_HEAD(&anon->d_u.d_child);
anon->d_flags &= ~DCACHE_DISCONNECTED;
}
/**
* d_materialise_unique - introduce an inode into the tree
* @dentry: candidate dentry
* @inode: inode to bind to the dentry, to which aliases may be attached
*
* Introduces an dentry into the tree, substituting an extant disconnected
* root directory alias in its place if there is one
*/
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
struct dentry *actual;
BUG_ON(!d_unhashed(dentry));
spin_lock(&dcache_lock);
if (!inode) {
actual = dentry;
dentry->d_inode = NULL;
goto found_lock;
}
if (S_ISDIR(inode->i_mode)) {
struct dentry *alias;
/* Does an aliased dentry already exist? */
alias = __d_find_alias(inode, 0);
if (alias) {
actual = alias;
/* Is this an anonymous mountpoint that we could splice
* into our tree? */
if (IS_ROOT(alias)) {
spin_lock(&alias->d_lock);
__d_materialise_dentry(dentry, alias);
__d_drop(alias);
goto found;
}
/* Nope, but we must(!) avoid directory aliasing */
actual = __d_unalias(dentry, alias);
if (IS_ERR(actual))
dput(alias);
goto out_nolock;
}
}
/* Add a unique reference */
actual = __d_instantiate_unique(dentry, inode);
if (!actual)
actual = dentry;
else if (unlikely(!d_unhashed(actual)))
goto shouldnt_be_hashed;
found_lock:
spin_lock(&actual->d_lock);
found:
_d_rehash(actual);
spin_unlock(&actual->d_lock);
spin_unlock(&dcache_lock);
out_nolock:
if (actual == dentry) {
security_d_instantiate(dentry, inode);
return NULL;
}
iput(inode);
return actual;
shouldnt_be_hashed:
spin_unlock(&dcache_lock);
BUG();
goto shouldnt_be_hashed;
}
/**
* d_path - return the path of a dentry
* @dentry: dentry to report
* @vfsmnt: vfsmnt to which the dentry belongs
* @root: root dentry
* @rootmnt: vfsmnt to which the root dentry belongs
* @buffer: buffer to return value in
* @buflen: buffer length
*
* Convert a dentry into an ASCII path name. If the entry has been deleted
* the string " (deleted)" is appended. Note that this is ambiguous.
*
* Returns the buffer or an error code if the path was too long.
*
* "buflen" should be positive. Caller holds the dcache_lock.
*/
static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
struct dentry *root, struct vfsmount *rootmnt,
char *buffer, int buflen)
{
char * end = buffer+buflen;
char * retval;
int namelen;
*--end = '\0';
buflen--;
if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
buflen -= 10;
end -= 10;
if (buflen < 0)
goto Elong;
memcpy(end, " (deleted)", 10);
}
if (buflen < 1)
goto Elong;
/* Get '/' right */
retval = end-1;
*retval = '/';
for (;;) {
struct dentry * parent;
if (dentry == root && vfsmnt == rootmnt)
break;
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
/* Global root? */
spin_lock(&vfsmount_lock);
if (vfsmnt->mnt_parent == vfsmnt) {
spin_unlock(&vfsmount_lock);
goto global_root;
}
dentry = vfsmnt->mnt_mountpoint;
vfsmnt = vfsmnt->mnt_parent;
spin_unlock(&vfsmount_lock);
continue;
}
parent = dentry->d_parent;
prefetch(parent);
namelen = dentry->d_name.len;
buflen -= namelen + 1;
if (buflen < 0)
goto Elong;
end -= namelen;
memcpy(end, dentry->d_name.name, namelen);
*--end = '/';
retval = end;
dentry = parent;
}
return retval;
global_root:
namelen = dentry->d_name.len;
buflen -= namelen;
if (buflen < 0)
goto Elong;
retval -= namelen-1; /* hit the slash */
memcpy(retval, dentry->d_name.name, namelen);
return retval;
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
/* write full pathname into buffer and return start of pathname */
char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
char *buf, int buflen)
{
char *res;
struct vfsmount *rootmnt;
struct dentry *root;
/*
* We have various synthetic filesystems that never get mounted. On
* these filesystems dentries are never used for lookup purposes, and
* thus don't need to be hashed. They also don't need a name until a
* user wants to identify the object in /proc/pid/fd/. The little hack
* below allows us to generate a name for these objects on demand:
*/
if (dentry->d_op && dentry->d_op->d_dname)
return dentry->d_op->d_dname(dentry, buf, buflen);
read_lock(&current->fs->lock);
rootmnt = mntget(current->fs->rootmnt);
root = dget(current->fs->root);
read_unlock(&current->fs->lock);
spin_lock(&dcache_lock);
res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
spin_unlock(&dcache_lock);
dput(root);
mntput(rootmnt);
return res;
}
/*
* Helper function for dentry_operations.d_dname() members
*/
char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
const char *fmt, ...)
{
va_list args;
char temp[64];
int sz;
va_start(args, fmt);
sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
va_end(args);
if (sz > sizeof(temp) || sz > buflen)
return ERR_PTR(-ENAMETOOLONG);
buffer += buflen - sz;
return memcpy(buffer, temp, sz);
}
/*
* NOTE! The user-level library version returns a
* character pointer. The kernel system call just
* returns the length of the buffer filled (which
* includes the ending '\0' character), or a negative
* error value. So libc would do something like
*
* char *getcwd(char * buf, size_t size)
* {
* int retval;
*
* retval = sys_getcwd(buf, size);
* if (retval >= 0)
* return buf;
* errno = -retval;
* return NULL;
* }
*/
asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
{
int error;
struct vfsmount *pwdmnt, *rootmnt;
struct dentry *pwd, *root;
char *page = (char *) __get_free_page(GFP_USER);
if (!page)
return -ENOMEM;
read_lock(&current->fs->lock);
pwdmnt = mntget(current->fs->pwdmnt);
pwd = dget(current->fs->pwd);
rootmnt = mntget(current->fs->rootmnt);
root = dget(current->fs->root);
read_unlock(&current->fs->lock);
error = -ENOENT;
/* Has the current directory has been unlinked? */
spin_lock(&dcache_lock);
if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
unsigned long len;
char * cwd;
cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
spin_unlock(&dcache_lock);
error = PTR_ERR(cwd);
if (IS_ERR(cwd))
goto out;
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
if (len <= size) {
error = len;
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
} else
spin_unlock(&dcache_lock);
out:
dput(pwd);
mntput(pwdmnt);
dput(root);
mntput(rootmnt);
free_page((unsigned long) page);
return error;
}
/*
* Test whether new_dentry is a subdirectory of old_dentry.
*
* Trivially implemented using the dcache structure
*/
/**
* is_subdir - is new dentry a subdirectory of old_dentry
* @new_dentry: new dentry
* @old_dentry: old dentry
*
* Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
* Returns 0 otherwise.
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
*/
int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
{
int result;
struct dentry * saved = new_dentry;
unsigned long seq;
/* need rcu_readlock to protect against the d_parent trashing due to
* d_move
*/
rcu_read_lock();
do {
/* for restarting inner loop in case of seq retry */
new_dentry = saved;
result = 0;
seq = read_seqbegin(&rename_lock);
for (;;) {
if (new_dentry != old_dentry) {
struct dentry * parent = new_dentry->d_parent;
if (parent == new_dentry)
break;
new_dentry = parent;
continue;
}
result = 1;
break;
}
} while (read_seqretry(&rename_lock, seq));
rcu_read_unlock();
return result;
}
void d_genocide(struct dentry *root)
{
struct dentry *this_parent = root;
struct list_head *next;
spin_lock(&dcache_lock);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
if (d_unhashed(dentry)||!dentry->d_inode)
continue;
if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
goto repeat;
}
atomic_dec(&dentry->d_count);
}
if (this_parent != root) {
next = this_parent->d_u.d_child.next;
atomic_dec(&this_parent->d_count);
this_parent = this_parent->d_parent;
goto resume;
}
spin_unlock(&dcache_lock);
}
/**
* find_inode_number - check for dentry with name
* @dir: directory to check
* @name: Name to find.
*
* Check whether a dentry already exists for the given name,
* and return the inode number if it has an inode. Otherwise
* 0 is returned.
*
* This routine is used to post-process directory listings for
* filesystems using synthetic inode numbers, and is necessary
* to keep getcwd() working.
*/
ino_t find_inode_number(struct dentry *dir, struct qstr *name)
{
struct dentry * dentry;
ino_t ino = 0;
dentry = d_hash_and_lookup(dir, name);
if (dentry) {
if (dentry->d_inode)
ino = dentry->d_inode->i_ino;
dput(dentry);
}
return ino;
}
static __initdata unsigned long dhash_entries;
static int __init set_dhash_entries(char *str)
{
if (!str)
return 0;
dhash_entries = simple_strtoul(str, &str, 0);
return 1;
}
__setup("dhash_entries=", set_dhash_entries);
static void __init dcache_init_early(void)
{
int loop;
/* If hashes are distributed across NUMA nodes, defer
* hash allocation until vmalloc space is available.
*/
if (hashdist)
return;
dentry_hashtable =
alloc_large_system_hash("Dentry cache",
sizeof(struct hlist_head),
dhash_entries,
13,
HASH_EARLY,
&d_hash_shift,
&d_hash_mask,
0);
for (loop = 0; loop < (1 << d_hash_shift); loop++)
INIT_HLIST_HEAD(&dentry_hashtable[loop]);
}
static void __init dcache_init(unsigned long mempages)
{
int loop;
/*
* A constructor could be added for stable state like the lists,
* but it is probably not worth it because of the cache nature
* of the dcache.
*/
dentry_cache = KMEM_CACHE(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
register_shrinker(&dcache_shrinker);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
return;
dentry_hashtable =
alloc_large_system_hash("Dentry cache",
sizeof(struct hlist_head),
dhash_entries,
13,
0,
&d_hash_shift,
&d_hash_mask,
0);
for (loop = 0; loop < (1 << d_hash_shift); loop++)
INIT_HLIST_HEAD(&dentry_hashtable[loop]);
}
/* SLAB cache for __getname() consumers */
struct kmem_cache *names_cachep __read_mostly;
/* SLAB cache for file structures */
struct kmem_cache *filp_cachep __read_mostly;
EXPORT_SYMBOL(d_genocide);
void __init vfs_caches_init_early(void)
{
dcache_init_early();
inode_init_early();
}
void __init vfs_caches_init(unsigned long mempages)
{
unsigned long reserve;
/* Base hash sizes on available memory, with a reserve equal to
150% of current kernel size */
reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
mempages -= reserve;
names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
dcache_init(mempages);
inode_init(mempages);
files_init(mempages);
mnt_init(mempages);
bdev_cache_init();
chrdev_init();
}
EXPORT_SYMBOL(d_alloc);
EXPORT_SYMBOL(d_alloc_anon);
EXPORT_SYMBOL(d_alloc_root);
EXPORT_SYMBOL(d_delete);
EXPORT_SYMBOL(d_find_alias);
EXPORT_SYMBOL(d_instantiate);
EXPORT_SYMBOL(d_invalidate);
EXPORT_SYMBOL(d_lookup);
EXPORT_SYMBOL(d_move);
EXPORT_SYMBOL_GPL(d_materialise_unique);
EXPORT_SYMBOL(d_path);
EXPORT_SYMBOL(d_prune_aliases);
EXPORT_SYMBOL(d_rehash);
EXPORT_SYMBOL(d_splice_alias);
EXPORT_SYMBOL(d_validate);
EXPORT_SYMBOL(dget_locked);
EXPORT_SYMBOL(dput);
EXPORT_SYMBOL(find_inode_number);
EXPORT_SYMBOL(have_submounts);
EXPORT_SYMBOL(names_cachep);
EXPORT_SYMBOL(shrink_dcache_parent);
EXPORT_SYMBOL(shrink_dcache_sb);
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