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kernfs: remove kernfs_addrm_cxt
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kernfs_addrm_cxt and the accompanying kernfs_addrm_start/finish() were
added because there were operations which should be performed outside
kernfs_mutex after adding and removing kernfs_nodes.  The necessary
operations were recorded in kernfs_addrm_cxt and performed by
kernfs_addrm_finish(); however, after the recent changes which
relocated deactivation and unmapping so that they're performed
directly during removal, the only operation kernfs_addrm_finish()
performs is kernfs_put(), which can be moved inside the removal path
too.

This patch moves the kernfs_put() of the base ref to __kernfs_remove()
and remove kernfs_addrm_cxt and kernfs_addrm_start/finish().

* kernfs_add_one() is updated to grab and release the parent's active
  ref and kernfs_mutex itself.  kernfs_get/put_active() and
  kernfs_addrm_start/finish() invocations around it are removed from
  all users.

* __kernfs_remove() puts an unlinked node directly instead of chaining
  it to kernfs_addrm_cxt.  Its callers are updated to grab and release
  kernfs_mutex instead of calling kernfs_addrm_start/finish() around
  it.

v2: Updated to fit the v2 restructuring of removal path.

Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@htejun @gregkh
htejun authored and gregkh committed Jan 10, 2014
1 parent f601f9a commit 99177a3
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Showing 5 changed files with 29 additions and 121 deletions.
114 changes: 26 additions & 88 deletions fs/kernfs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -398,72 +398,46 @@ struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
return NULL;
}

/**
* kernfs_addrm_start - prepare for kernfs_node add/remove
* @acxt: pointer to kernfs_addrm_cxt to be used
*
* This function is called when the caller is about to add or remove
* kernfs_node. This function acquires kernfs_mutex. @acxt is used
* to keep and pass context to other addrm functions.
*
* LOCKING:
* Kernel thread context (may sleep). kernfs_mutex is locked on
* return.
*/
void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
__acquires(kernfs_mutex)
{
memset(acxt, 0, sizeof(*acxt));

mutex_lock(&kernfs_mutex);
}

/**
* kernfs_add_one - add kernfs_node to parent without warning
* @acxt: addrm context to use
* @kn: kernfs_node to be added
* @parent: the parent kernfs_node to add @kn to
*
* Get @parent and set @kn->parent to it and increment nlink of the
* parent inode if @kn is a directory and link into the children list
* of the parent.
*
* This function should be called between calls to
* kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
* the same @acxt as passed to kernfs_addrm_start().
*
* LOCKING:
* Determined by kernfs_addrm_start().
*
* RETURNS:
* 0 on success, -EEXIST if entry with the given name already
* exists.
*/
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
struct kernfs_node *parent)
int kernfs_add_one(struct kernfs_node *kn, struct kernfs_node *parent)
{
bool has_ns = kernfs_ns_enabled(parent);
struct kernfs_iattrs *ps_iattr;
bool has_ns;
int ret;

WARN_ON_ONCE(atomic_read(&parent->active) < 0);
if (!kernfs_get_active(parent))
return -ENOENT;

if (has_ns != (bool)kn->ns) {
WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
has_ns ? "required" : "invalid", parent->name, kn->name);
return -EINVAL;
}
mutex_lock(&kernfs_mutex);

ret = -EINVAL;
has_ns = kernfs_ns_enabled(parent);
if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
has_ns ? "required" : "invalid", parent->name, kn->name))
goto out_unlock;

if (kernfs_type(parent) != KERNFS_DIR)
return -EINVAL;
goto out_unlock;

kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = parent;
kernfs_get(parent);

ret = kernfs_link_sibling(kn);
if (ret)
return ret;
goto out_unlock;

/* Update timestamps on the parent */
ps_iattr = parent->iattr;
Expand All @@ -474,34 +448,11 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,

/* Mark the entry added into directory tree */
atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
return 0;
}

/**
* kernfs_addrm_finish - finish up kernfs_node add/remove
* @acxt: addrm context to finish up
*
* Finish up kernfs_node add/remove. Resources acquired by
* kernfs_addrm_start() are released and removed kernfs_nodes are
* cleaned up.
*
* LOCKING:
* kernfs_mutex is released.
*/
void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
__releases(kernfs_mutex)
{
/* release resources acquired by kernfs_addrm_start() */
ret = 0;
out_unlock:
mutex_unlock(&kernfs_mutex);

/* kill removed kernfs_nodes */
while (acxt->removed) {
struct kernfs_node *kn = acxt->removed;

acxt->removed = kn->u.removed_list;

kernfs_put(kn);
}
kernfs_put_active(parent);
return ret;
}

/**
Expand Down Expand Up @@ -633,7 +584,6 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
const char *name, umode_t mode,
void *priv, const void *ns)
{
struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
int rc;

Expand All @@ -648,14 +598,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
kn->priv = priv;

/* link in */
rc = -ENOENT;
if (kernfs_get_active(parent)) {
kernfs_addrm_start(&acxt);
rc = kernfs_add_one(&acxt, kn, parent);
kernfs_addrm_finish(&acxt);
kernfs_put_active(parent);
}

rc = kernfs_add_one(kn, parent);
if (!rc)
return kn;

Expand Down Expand Up @@ -841,8 +784,7 @@ static void __kernfs_deactivate(struct kernfs_node *kn)
}
}

static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
struct kernfs_node *kn)
static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;

Expand Down Expand Up @@ -890,8 +832,7 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
}

pos->u.removed_list = acxt->removed;
acxt->removed = pos;
kernfs_put(pos);
}

kernfs_put(pos);
Expand All @@ -906,11 +847,9 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
*/
void kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_addrm_cxt acxt;

kernfs_addrm_start(&acxt);
__kernfs_remove(&acxt, kn);
kernfs_addrm_finish(&acxt);
mutex_lock(&kernfs_mutex);
__kernfs_remove(kn);
mutex_unlock(&kernfs_mutex);
}

/**
Expand All @@ -925,7 +864,6 @@ void kernfs_remove(struct kernfs_node *kn)
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{
struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;

if (!parent) {
Expand All @@ -934,13 +872,13 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
return -ENOENT;
}

kernfs_addrm_start(&acxt);
mutex_lock(&kernfs_mutex);

kn = kernfs_find_ns(parent, name, ns);
if (kn)
__kernfs_remove(&acxt, kn);
__kernfs_remove(kn);

kernfs_addrm_finish(&acxt);
mutex_unlock(&kernfs_mutex);

if (kn)
return 0;
Expand Down
10 changes: 1 addition & 9 deletions fs/kernfs/file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -817,7 +817,6 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
bool name_is_static,
struct lock_class_key *key)
{
struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
unsigned flags;
int rc;
Expand Down Expand Up @@ -853,14 +852,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
if (ops->mmap)
kn->flags |= KERNFS_HAS_MMAP;

rc = -ENOENT;
if (kernfs_get_active(parent)) {
kernfs_addrm_start(&acxt);
rc = kernfs_add_one(&acxt, kn, parent);
kernfs_addrm_finish(&acxt);
kernfs_put_active(parent);
}

rc = kernfs_add_one(kn, parent);
if (rc) {
kernfs_put(kn);
return ERR_PTR(rc);
Expand Down
12 changes: 1 addition & 11 deletions fs/kernfs/kernfs-internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -45,13 +45,6 @@ static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
return kn->dir.root;
}

/*
* Context structure to be used while adding/removing nodes.
*/
struct kernfs_addrm_cxt {
struct kernfs_node *removed;
};

/*
* mount.c
*/
Expand Down Expand Up @@ -101,10 +94,7 @@ extern const struct inode_operations kernfs_dir_iops;

struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
void kernfs_put_active(struct kernfs_node *kn);
void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt);
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
struct kernfs_node *parent);
void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt);
int kernfs_add_one(struct kernfs_node *kn, struct kernfs_node *parent);
struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
umode_t mode, unsigned flags);

Expand Down
10 changes: 1 addition & 9 deletions fs/kernfs/symlink.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
struct kernfs_node *target)
{
struct kernfs_node *kn;
struct kernfs_addrm_cxt acxt;
int error;

kn = kernfs_new_node(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
Expand All @@ -40,14 +39,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
kn->symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */

error = -ENOENT;
if (kernfs_get_active(parent)) {
kernfs_addrm_start(&acxt);
error = kernfs_add_one(&acxt, kn, parent);
kernfs_addrm_finish(&acxt);
kernfs_put_active(parent);
}

error = kernfs_add_one(kn, parent);
if (!error)
return kn;

Expand Down
4 changes: 0 additions & 4 deletions include/linux/kernfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,10 +89,6 @@ struct kernfs_node {

struct rb_node rb;

union {
struct kernfs_node *removed_list;
} u;

const void *ns; /* namespace tag */
unsigned int hash; /* ns + name hash */
union {
Expand Down

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