/*
* 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/config.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/malloc.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/cache.h>
#include <asm/uaccess.h>
#define DCACHE_PARANOIA 1
/* #define DCACHE_DEBUG 1 */
spinlock_t dcache_lock = SPIN_LOCK_UNLOCKED;
/* Right now the dcache depends on the kernel lock */
#define check_lock() if (!kernel_locked()) BUG()
static kmem_cache_t *dentry_cache;
/*
* 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;
static unsigned int d_hash_shift;
static struct list_head *dentry_hashtable;
static LIST_HEAD(dentry_unused);
struct {
int nr_dentry;
int nr_unused;
int age_limit; /* age in seconds */
int want_pages; /* pages requested by system */
int dummy[2];
} dentry_stat = {0, 0, 45, 0,};
/* no dcache_lock, please */
64 static inline void d_free(struct dentry *dentry)
{
66 if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
68 if (dname_external(dentry))
kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry);
dentry_stat.nr_dentry--;
}
/*
* Release the dentry's inode, using the fileystem
* d_iput() operation if defined.
* Called with dcache_lock held, drops it.
*/
79 static inline void dentry_iput(struct dentry * dentry)
{
struct inode *inode = dentry->d_inode;
82 if (inode) {
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
85 spin_unlock(&dcache_lock);
86 if (dentry->d_op && dentry->d_op->d_iput)
dentry->d_op->d_iput(dentry, inode);
88 else
iput(inode);
90 } else
91 spin_unlock(&dcache_lock);
}
/*
* 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.
*/
123 void dput(struct dentry *dentry)
{
125 if (!dentry)
126 return;
repeat:
129 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
130 return;
/* dput on a free dentry? */
133 if (!list_empty(&dentry->d_lru))
134 BUG();
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
138 if (dentry->d_op && dentry->d_op->d_delete) {
139 if (dentry->d_op->d_delete(dentry))
140 goto unhash_it;
}
/* Unreachable? Get rid of it */
143 if (list_empty(&dentry->d_hash))
144 goto kill_it;
list_add(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
/*
* Update the timestamp
*/
dentry->d_reftime = jiffies;
151 spin_unlock(&dcache_lock);
152 return;
unhash_it:
list_del_init(&dentry->d_hash);
kill_it: {
struct dentry *parent;
list_del(&dentry->d_child);
/* drops the lock, at that point nobody can reach this dentry */
dentry_iput(dentry);
parent = dentry->d_parent;
d_free(dentry);
164 if (dentry == parent)
165 return;
dentry = parent;
167 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.
*/
183 int d_invalidate(struct dentry * dentry)
{
/*
* If it's already been dropped, return OK.
*/
spin_lock(&dcache_lock);
189 if (list_empty(&dentry->d_hash)) {
190 spin_unlock(&dcache_lock);
191 return 0;
}
/*
* Check whether to do a partial shrink_dcache
* to get rid of unused child entries.
*/
197 if (!list_empty(&dentry->d_subdirs)) {
198 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).
*/
213 if (atomic_read(&dentry->d_count) > 1) {
214 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
215 spin_unlock(&dcache_lock);
216 return -EBUSY;
}
}
list_del_init(&dentry->d_hash);
221 spin_unlock(&dcache_lock);
222 return 0;
}
/* This should be called _only_ with dcache_lock held */
227 static inline struct dentry * __dget_locked(struct dentry *dentry)
{
atomic_inc(&dentry->d_count);
230 if (atomic_read(&dentry->d_count) == 1) {
dentry_stat.nr_unused--;
list_del(&dentry->d_lru);
233 INIT_LIST_HEAD(&dentry->d_lru); /* make "list_empty()" work */
}
235 return dentry;
}
238 struct dentry * dget_locked(struct dentry *dentry)
{
240 return __dget_locked(dentry);
}
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
*
* If inode has a hashed 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.
*/
253 struct dentry * d_find_alias(struct inode *inode)
{
struct list_head *head, *next, *tmp;
struct dentry *alias;
spin_lock(&dcache_lock);
head = &inode->i_dentry;
next = inode->i_dentry.next;
261 while (next != head) {
tmp = next;
next = tmp->next;
alias = list_entry(tmp, struct dentry, d_alias);
265 if (!list_empty(&alias->d_hash)) {
__dget_locked(alias);
267 spin_unlock(&dcache_lock);
268 return alias;
}
}
271 spin_unlock(&dcache_lock);
272 return NULL;
}
/*
* Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.
*/
279 void d_prune_aliases(struct inode *inode)
{
struct list_head *tmp, *head = &inode->i_dentry;
restart:
spin_lock(&dcache_lock);
tmp = head;
285 while ((tmp = tmp->next) != head) {
struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
287 if (!atomic_read(&dentry->d_count)) {
__dget_locked(dentry);
289 spin_unlock(&dcache_lock);
d_drop(dentry);
dput(dentry);
292 goto restart;
}
}
295 spin_unlock(&dcache_lock);
}
/*
* Throw away a dentry - free the inode, dput the parent.
* This requires that the LRU list has already been
* removed.
* Called with dcache_lock, drops it and then regains.
*/
304 static inline void prune_one_dentry(struct dentry * dentry)
{
struct dentry * parent;
list_del_init(&dentry->d_hash);
list_del(&dentry->d_child);
dentry_iput(dentry);
parent = dentry->d_parent;
d_free(dentry);
313 if (parent != dentry)
dput(parent);
spin_lock(&dcache_lock);
}
/**
* prune_dcache - shrink the dcache
* @count: number of entries to try and free
*
* 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.
*/
331 void prune_dcache(int count)
{
spin_lock(&dcache_lock);
334 for (;;) {
struct dentry *dentry;
struct list_head *tmp;
tmp = dentry_unused.prev;
340 if (tmp == &dentry_unused)
341 break;
list_del_init(tmp);
dentry = list_entry(tmp, struct dentry, d_lru);
/* If the dentry was recently referenced, don't free it. */
346 if (dentry->d_flags & DCACHE_REFERENCED) {
dentry->d_flags &= ~DCACHE_REFERENCED;
list_add(&dentry->d_lru, &dentry_unused);
count--;
350 continue;
}
dentry_stat.nr_unused--;
/* Unused dentry with a count? */
355 if (atomic_read(&dentry->d_count))
356 BUG();
prune_one_dentry(dentry);
359 if (!--count)
360 break;
}
362 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
*/
387 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);
next = dentry_unused.next;
398 while (next != &dentry_unused) {
tmp = next;
next = tmp->next;
dentry = list_entry(tmp, struct dentry, d_lru);
402 if (dentry->d_sb != sb)
403 continue;
list_del(tmp);
list_add(tmp, &dentry_unused);
}
/*
* Pass two ... free the dentries for this superblock.
*/
repeat:
next = dentry_unused.next;
413 while (next != &dentry_unused) {
tmp = next;
next = tmp->next;
dentry = list_entry(tmp, struct dentry, d_lru);
417 if (dentry->d_sb != sb)
418 continue;
419 if (atomic_read(&dentry->d_count))
420 continue;
dentry_stat.nr_unused--;
list_del(tmp);
423 INIT_LIST_HEAD(tmp);
prune_one_dentry(dentry);
425 goto repeat;
}
427 spin_unlock(&dcache_lock);
}
/*
* 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
*/
444 int have_submounts(struct dentry *parent)
{
struct dentry *this_parent = parent;
struct list_head *next;
spin_lock(&dcache_lock);
450 if (d_mountpoint(parent))
451 goto positive;
repeat:
next = this_parent->d_subdirs.next;
resume:
455 while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
/* Have we found a mount point ? */
460 if (d_mountpoint(dentry))
461 goto positive;
462 if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
464 goto repeat;
}
}
/*
* All done at this level ... ascend and resume the search.
*/
470 if (this_parent != parent) {
next = this_parent->d_child.next;
this_parent = this_parent->d_parent;
473 goto resume;
}
475 spin_unlock(&dcache_lock);
476 return 0; /* No mount points found in tree */
positive:
478 spin_unlock(&dcache_lock);
479 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.
*/
489 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:
499 while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
503 if (!atomic_read(&dentry->d_count)) {
list_del(&dentry->d_lru);
list_add(&dentry->d_lru, dentry_unused.prev);
found++;
}
/*
* Descend a level if the d_subdirs list is non-empty.
*/
511 if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
#ifdef DCACHE_DEBUG
printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n",
dentry->d_parent->d_name.name, dentry->d_name.name, found);
#endif
517 goto repeat;
}
}
/*
* All done at this level ... ascend and resume the search.
*/
523 if (this_parent != parent) {
next = this_parent->d_child.next;
this_parent = this_parent->d_parent;
#ifdef DCACHE_DEBUG
printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n",
this_parent->d_parent->d_name.name, this_parent->d_name.name, found);
#endif
530 goto resume;
}
532 spin_unlock(&dcache_lock);
533 return found;
}
/**
* shrink_dcache_parent - prune dcache
* @parent: parent of entries to prune
*
* Prune the dcache to remove unused children of the parent dentry.
*/
543 void shrink_dcache_parent(struct dentry * parent)
{
int found;
547 while ((found = select_parent(parent)) != 0)
prune_dcache(found);
}
/*
* This is called from kswapd when we think we need some
* more memory, but aren't really sure how much. So we
* carefully try to free a _bit_ of our dcache, but not
* too much.
*
* Priority:
* 0 - very urgent: shrink everything
* ...
* 6 - base-level: try to shrink a bit.
*/
562 void shrink_dcache_memory(int priority, unsigned int gfp_mask)
{
int count = 0;
/*
* Nasty deadlock avoidance.
*
* 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.
*
* We should make sure we don't hold the superblock lock over
* block allocations, but for now:
*/
577 if (!(gfp_mask & __GFP_IO))
578 return;
580 if (priority)
count = dentry_stat.nr_unused / priority;
prune_dcache(count);
kmem_cache_shrink(dentry_cache);
}
#define NAME_ALLOC_LEN(len) ((len+16) & ~15)
/**
* 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.
*/
599 struct dentry * d_alloc(struct dentry * parent, const struct qstr *name)
{
char * str;
struct dentry *dentry;
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
605 if (!dentry)
606 return NULL;
608 if (name->len > DNAME_INLINE_LEN-1) {
str = kmalloc(NAME_ALLOC_LEN(name->len), GFP_KERNEL);
610 if (!str) {
kmem_cache_free(dentry_cache, dentry);
612 return NULL;
}
614 } else
str = dentry->d_iname;
memcpy(str, name->name, name->len);
str[name->len] = 0;
atomic_set(&dentry->d_count, 1);
dentry->d_flags = 0;
dentry->d_inode = NULL;
dentry->d_parent = NULL;
dentry->d_sb = NULL;
dentry->d_name.name = str;
dentry->d_name.len = name->len;
dentry->d_name.hash = name->hash;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
630 INIT_LIST_HEAD(&dentry->d_vfsmnt);
631 INIT_LIST_HEAD(&dentry->d_hash);
632 INIT_LIST_HEAD(&dentry->d_lru);
633 INIT_LIST_HEAD(&dentry->d_subdirs);
634 INIT_LIST_HEAD(&dentry->d_alias);
635 if (parent) {
dentry->d_parent = dget(parent);
dentry->d_sb = parent->d_sb;
spin_lock(&dcache_lock);
list_add(&dentry->d_child, &parent->d_subdirs);
640 spin_unlock(&dcache_lock);
641 } else
642 INIT_LIST_HEAD(&dentry->d_child);
dentry_stat.nr_dentry++;
645 return dentry;
}
/**
* 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.
*/
663 void d_instantiate(struct dentry *entry, struct inode * inode)
{
spin_lock(&dcache_lock);
666 if (inode)
list_add(&entry->d_alias, &inode->i_dentry);
entry->d_inode = inode;
669 spin_unlock(&dcache_lock);
}
/**
* 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.
*/
681 struct dentry * d_alloc_root(struct inode * root_inode)
{
struct dentry *res = NULL;
685 if (root_inode) {
res = d_alloc(NULL, &(const struct qstr) { "/", 1, 0 });
687 if (res) {
res->d_sb = root_inode->i_sb;
res->d_parent = res;
d_instantiate(res, root_inode);
}
}
693 return res;
}
696 static inline struct list_head * d_hash(struct dentry * parent, unsigned long hash)
{
hash += (unsigned long) parent / L1_CACHE_BYTES;
hash = hash ^ (hash >> D_HASHBITS) ^ (hash >> D_HASHBITS*2);
700 return dentry_hashtable + (hash & D_HASHMASK);
}
/**
* 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.
*/
714 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 list_head *head = d_hash(parent,hash);
struct list_head *tmp;
spin_lock(&dcache_lock);
tmp = head->next;
724 for (;;) {
struct dentry * dentry = list_entry(tmp, struct dentry, d_hash);
726 if (tmp == head)
727 break;
tmp = tmp->next;
729 if (dentry->d_name.hash != hash)
730 continue;
731 if (dentry->d_parent != parent)
732 continue;
733 if (parent->d_op && parent->d_op->d_compare) {
734 if (parent->d_op->d_compare(parent, &dentry->d_name, name))
735 continue;
736 } else {
737 if (dentry->d_name.len != len)
738 continue;
739 if (memcmp(dentry->d_name.name, str, len))
740 continue;
}
__dget_locked(dentry);
dentry->d_flags |= DCACHE_REFERENCED;
744 spin_unlock(&dcache_lock);
745 return dentry;
}
747 spin_unlock(&dcache_lock);
748 return NULL;
}
/**
* d_validate - verify dentry provided from insecure source
* @dentry: The dentry alleged to be valid
* @dparent: The parent dentry
* @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.
*
* NOTE: This function does _not_ dereference the pointers before we have
* validated them. We can test the pointer values, but we
* must not actually use them until we have found a valid
* copy of the pointer in kernel space..
*/
768 int d_validate(struct dentry *dentry, struct dentry *dparent,
unsigned int hash, unsigned int len)
{
struct list_head *base, *lhp;
int valid = 1;
spin_lock(&dcache_lock);
775 if (dentry != dparent) {
base = d_hash(dparent, hash);
lhp = base;
778 while ((lhp = lhp->next) != base) {
779 if (dentry == list_entry(lhp, struct dentry, d_hash)) {
__dget_locked(dentry);
781 goto out;
}
}
784 } else {
/*
* Special case: local mount points don't live in
* the hashes, so we search the super blocks.
*/
struct super_block *sb = sb_entry(super_blocks.next);
791 for (; sb != sb_entry(&super_blocks);
sb = sb_entry(sb->s_list.next)) {
if (!sb->s_dev)
continue;
if (sb->s_root == dentry) {
__dget_locked(dentry);
goto out;
}
}
}
valid = 0;
out:
803 spin_unlock(&dcache_lock);
804 return valid;
}
/*
* 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
*/
828 void d_delete(struct dentry * dentry)
{
/*
* Are we the only user?
*/
spin_lock(&dcache_lock);
834 if (atomic_read(&dentry->d_count) == 1) {
dentry_iput(dentry);
836 return;
}
838 spin_unlock(&dcache_lock);
/*
* If not, just drop the dentry and let dput
* pick up the tab..
*/
d_drop(dentry);
}
/**
* 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.
*/
854 void d_rehash(struct dentry * entry)
{
struct list_head *list = d_hash(entry->d_parent, entry->d_name.hash);
spin_lock(&dcache_lock);
list_add(&entry->d_hash, list);
859 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..
*/
877 static inline void switch_names(struct dentry * dentry, struct dentry * target)
{
const unsigned char *old_name, *new_name;
881 check_lock();
memcpy(dentry->d_iname, target->d_iname, DNAME_INLINE_LEN);
old_name = target->d_name.name;
new_name = dentry->d_name.name;
885 if (old_name == target->d_iname)
old_name = dentry->d_iname;
887 if (new_name == dentry->d_iname)
new_name = target->d_iname;
target->d_name.name = new_name;
dentry->d_name.name = old_name;
}
/*
* 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.
*
* Careful with the hash switch. The hash switch depends on
* the fact that any list-entry can be a head of the list.
* Think about it.
*/
/**
* 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.
*/
918 void d_move(struct dentry * dentry, struct dentry * target)
{
920 check_lock();
922 if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
spin_lock(&dcache_lock);
/* Move the dentry to the target hash queue */
list_del(&dentry->d_hash);
list_add(&dentry->d_hash, &target->d_hash);
/* Unhash the target: dput() will then get rid of it */
list_del(&target->d_hash);
932 INIT_LIST_HEAD(&target->d_hash);
list_del(&dentry->d_child);
list_del(&target->d_child);
/* Switch the parents and the names.. */
switch_names(dentry, target);
939 do_switch(dentry->d_parent, target->d_parent);
940 do_switch(dentry->d_name.len, target->d_name.len);
941 do_switch(dentry->d_name.hash, target->d_name.hash);
/* And add them back to the (new) parent lists */
list_add(&target->d_child, &target->d_parent->d_subdirs);
list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
946 spin_unlock(&dcache_lock);
}
/**
* 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.
*
* "buflen" should be %PAGE_SIZE or more. Caller holds the dcache_lock.
*/
964 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--;
974 if (!IS_ROOT(dentry) && list_empty(&dentry->d_hash)) {
buflen -= 10;
end -= 10;
memcpy(end, " (deleted)", 10);
}
/* Get '/' right */
retval = end-1;
*retval = '/';
984 for (;;) {
struct dentry * parent;
987 if (dentry == root && vfsmnt == rootmnt)
988 break;
989 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
/* Global root? */
991 if (vfsmnt->mnt_parent == vfsmnt)
992 goto global_root;
dentry = vfsmnt->mnt_mountpoint;
vfsmnt = vfsmnt->mnt_parent;
995 continue;
}
parent = dentry->d_parent;
namelen = dentry->d_name.len;
buflen -= namelen + 1;
1000 if (buflen < 0)
1001 break;
end -= namelen;
memcpy(end, dentry->d_name.name, namelen);
*--end = '/';
retval = end;
dentry = parent;
}
1008 return retval;
global_root:
namelen = dentry->d_name.len;
buflen -= namelen;
1012 if (buflen >= 0) {
retval -= namelen-1; /* hit the slash */
memcpy(retval, dentry->d_name.name, namelen);
}
1016 return retval;
}
/*
* 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;
* }
*/
1037 asmlinkage long sys_getcwd(char *buf, unsigned long size)
{
int error;
struct vfsmount *pwdmnt, *rootmnt;
struct dentry *pwd, *root;
char *page = (char *) __get_free_page(GFP_USER);
1044 if (!page)
1045 return -ENOMEM;
read_lock(¤t->fs->lock);
pwdmnt = mntget(current->fs->pwdmnt);
pwd = dget(current->fs->pwd);
rootmnt = mntget(current->fs->rootmnt);
root = dget(current->fs->root);
1052 read_unlock(¤t->fs->lock);
error = -ENOENT;
/* Has the current directory has been unlinked? */
spin_lock(&dcache_lock);
1057 if (pwd->d_parent == pwd || !list_empty(&pwd->d_hash)) {
unsigned long len;
char * cwd;
cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1062 spin_unlock(&dcache_lock);
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
1066 if (len <= size) {
error = len;
1068 if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
1071 } else
1072 spin_unlock(&dcache_lock);
dput(pwd);
mntput(pwdmnt);
dput(root);
mntput(rootmnt);
free_page((unsigned long) page);
1078 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.
*/
1096 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
{
int result;
result = 0;
1101 for (;;) {
1102 if (new_dentry != old_dentry) {
struct dentry * parent = new_dentry->d_parent;
1104 if (parent == new_dentry)
1105 break;
new_dentry = parent;
1107 continue;
}
result = 1;
1110 break;
}
1112 return result;
}
1115 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:
1124 while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
1128 if (d_unhashed(dentry)||!dentry->d_inode)
1129 continue;
1130 if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
1132 goto repeat;
}
atomic_dec(&dentry->d_count);
}
1136 if (this_parent != root) {
next = this_parent->d_child.next;
atomic_dec(&this_parent->d_count);
this_parent = this_parent->d_parent;
1140 goto resume;
}
1142 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.
*/
1159 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
{
struct dentry * dentry;
ino_t ino = 0;
/*
* 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);
1170 if (dir->d_op && dir->d_op->d_hash)
{
1172 if (dir->d_op->d_hash(dir, name) != 0)
1173 goto out;
}
dentry = d_lookup(dir, name);
1177 if (dentry)
{
1179 if (dentry->d_inode)
ino = dentry->d_inode->i_ino;
dput(dentry);
}
out:
1184 return ino;
}
1187 static void __init dcache_init(unsigned long mempages)
{
struct list_head *d;
unsigned long order;
unsigned int nr_hash;
int i;
/*
* 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.
* If fragmentation is too bad then the SLAB_HWCACHE_ALIGN
* flag could be removed here, to hint to the allocator that
* it should not try to get multiple page regions.
*/
dentry_cache = kmem_cache_create("dentry_cache",
sizeof(struct dentry),
0,
SLAB_HWCACHE_ALIGN,
NULL, NULL);
1207 if (!dentry_cache)
panic("Cannot create dentry cache");
#if PAGE_SHIFT < 13
mempages >>= (13 - PAGE_SHIFT);
#endif
mempages *= sizeof(struct list_head);
1214 for (order = 0; ((1UL << order) << PAGE_SHIFT) < mempages; order++)
;
1217 do {
unsigned long tmp;
nr_hash = (1UL << order) * PAGE_SIZE /
sizeof(struct list_head);
d_hash_mask = (nr_hash - 1);
tmp = nr_hash;
d_hash_shift = 0;
1226 while ((tmp >>= 1UL) != 0UL)
d_hash_shift++;
dentry_hashtable = (struct list_head *)
__get_free_pages(GFP_ATOMIC, order);
1231 } while (dentry_hashtable == NULL && --order >= 0);
printk("Dentry-cache hash table entries: %d (order: %ld, %ld bytes)\n",
nr_hash, order, (PAGE_SIZE << order));
1236 if (!dentry_hashtable)
panic("Failed to allocate dcache hash table\n");
d = dentry_hashtable;
i = nr_hash;
1241 do {
1242 INIT_LIST_HEAD(d);
d++;
i--;
1245 } while (i);
}
/* SLAB cache for __getname() consumers */
kmem_cache_t *names_cachep;
/* SLAB cache for file structures */
kmem_cache_t *filp_cachep;
/* SLAB cache for dquot structures */
kmem_cache_t *dquot_cachep;
/* SLAB cache for buffer_head structures */
kmem_cache_t *bh_cachep;
1260 void __init vfs_caches_init(unsigned long mempages)
{
bh_cachep = kmem_cache_create("buffer_head",
sizeof(struct buffer_head), 0,
SLAB_HWCACHE_ALIGN, NULL, NULL);
1265 if(!bh_cachep)
panic("Cannot create buffer head SLAB cache");
names_cachep = kmem_cache_create("names_cache",
PATH_MAX + 1, 0,
SLAB_HWCACHE_ALIGN, NULL, NULL);
1271 if (!names_cachep)
panic("Cannot create names SLAB cache");
filp_cachep = kmem_cache_create("filp",
sizeof(struct file), 0,
SLAB_HWCACHE_ALIGN, NULL, NULL);
1277 if(!filp_cachep)
panic("Cannot create filp SLAB cache");
#if defined (CONFIG_QUOTA)
dquot_cachep = kmem_cache_create("dquot",
sizeof(struct dquot), sizeof(unsigned long) * 4,
SLAB_HWCACHE_ALIGN, NULL, NULL);
if (!dquot_cachep)
panic("Cannot create dquot SLAB cache");
#endif
dcache_init(mempages);
}