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Commit f6acf8bb authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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sysfs, kernfs: introduce kernfs_ops 



We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly.  This patch
introduces kernfs_ops which hosts methods kernfs users implement and
updates fs/sysfs/file.c such that sysfs_kf_*() functions populate
kernfs_ops and kernfs_file_*() functions call the matching entries
from kernfs_ops.

kernfs_ops contains the following groups of methods.

* seq_show() - for kernfs files which use seq_file for reads.

* read() - for direct read implementations.  Used iff seq_show() is
  not implemented.

* write() - for writes.

* mmap() - for mmaps.

Notes:

* sysfs_elem_attr->ops is added so that kernfs_ops can be accessed
  from sysfs_dirent.  kernfs_ops() helper is added to verify locking
  and access the field.

* SYSFS_FLAG_HAS_(SEQ_SHOW|MMAP) added.  sd->s_attr->ops is accessible
  only while holding active_ref and there are cases where we want to
  take different actions depending on which ops are implemented.
  These two flags cache whether the two ops are implemented for those.

* kernfs_file_*() no longer test sysfs type but chooses different
  behaviors depending on which methods in kernfs_ops are implemented.
  The conversions are trivial except for the open path.  As
  kernfs_file_open() now decides whether to allow read/write accesses
  depending on the kernfs_ops implemented, the presence of methods in
  kobjs and attribute_bin should be propagated to kernfs_ops.
  sysfs_add_file_mode_ns() is updated so that it propagates presence /
  absence of the callbacks through _empty, _ro, _wo, _rw kernfs_ops.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent dd8a5b03

fs/sysfs/file.c

+112 −34
Original line number Diff line number Diff line
@@ -57,6 +57,17 @@ static struct sysfs_open_file *sysfs_of(struct file *file) 
	return ((struct seq_file *)file->private_data)->private;

}



/*

 * Determine the kernfs_ops for the given sysfs_dirent.  This function must

 * be called while holding an active reference.

 */

static const struct kernfs_ops *kernfs_ops(struct sysfs_dirent *sd)

{

	if (!sysfs_ignore_lockdep(sd))

		lockdep_assert_held(sd);

	return sd->s_attr.ops;

}



/*

 * Determine ktype->sysfs_ops for the given sysfs_dirent.  This function

 * must be called while holding an active reference.
@@ -180,7 +191,7 @@ static int kernfs_seq_show(struct seq_file *sf, void *v) 


	of->event = atomic_read(&of->sd->s_attr.open->event);



	return sysfs_kf_seq_show(sf, v);

	return of->sd->s_attr.ops->seq_show(sf, v);

}



static const struct seq_operations kernfs_seq_ops = {
@@ -201,6 +212,7 @@ static ssize_t kernfs_file_direct_read(struct sysfs_open_file *of, 
				       loff_t *ppos)

{

	ssize_t len = min_t(size_t, count, PAGE_SIZE);

	const struct kernfs_ops *ops;

	char *buf;



	buf = kmalloc(len, GFP_KERNEL);
@@ -218,7 +230,11 @@ static ssize_t kernfs_file_direct_read(struct sysfs_open_file *of, 
		goto out_free;

	}



	len = sysfs_kf_bin_read(of, buf, len, *ppos);

	ops = kernfs_ops(of->sd);

	if (ops->read)

		len = ops->read(of, buf, len, *ppos);

	else

		len = -EINVAL;



	sysfs_put_active(of->sd);

	mutex_unlock(&of->mutex);
@@ -250,10 +266,10 @@ static ssize_t kernfs_file_read(struct file *file, char __user *user_buf, 
{

	struct sysfs_open_file *of = sysfs_of(file);



	if (sysfs_is_bin(of->sd))

		return kernfs_file_direct_read(of, user_buf, count, ppos);

	else

	if (of->sd->s_flags & SYSFS_FLAG_HAS_SEQ_SHOW)

		return seq_read(file, user_buf, count, ppos);

	else

		return kernfs_file_direct_read(of, user_buf, count, ppos);

}



/* kernfs write callback for regular sysfs files */
@@ -312,6 +328,7 @@ static ssize_t kernfs_file_write(struct file *file, const char __user *user_buf, 
{

	struct sysfs_open_file *of = sysfs_of(file);

	ssize_t len = min_t(size_t, count, PAGE_SIZE);

	const struct kernfs_ops *ops;

	char *buf;



	buf = kmalloc(len + 1, GFP_KERNEL);
@@ -335,10 +352,11 @@ static ssize_t kernfs_file_write(struct file *file, const char __user *user_buf, 
		goto out_free;

	}



	if (sysfs_is_bin(of->sd))

		len = sysfs_kf_bin_write(of, buf, len, *ppos);

	ops = kernfs_ops(of->sd);

	if (ops->write)

		len = ops->write(of, buf, len, *ppos);

	else

		len = sysfs_kf_write(of, buf, len, *ppos);

		len = -EINVAL;



	sysfs_put_active(of->sd);

	mutex_unlock(&of->mutex);
@@ -524,6 +542,7 @@ static const struct vm_operations_struct kernfs_vm_ops = { 
static int kernfs_file_mmap(struct file *file, struct vm_area_struct *vma)

{

	struct sysfs_open_file *of = sysfs_of(file);

	const struct kernfs_ops *ops;

	int rc;



	mutex_lock(&of->mutex);
@@ -532,8 +551,9 @@ static int kernfs_file_mmap(struct file *file, struct vm_area_struct *vma) 
	if (!sysfs_get_active(of->sd))

		goto out_unlock;



	if (sysfs_is_bin(of->sd))

		rc = sysfs_kf_bin_mmap(of, vma);

	ops = kernfs_ops(of->sd);

	if (ops->mmap)

		rc = ops->mmap(of, vma);

	if (rc)

		goto out_put;
@@ -660,34 +680,19 @@ static void sysfs_put_open_dirent(struct sysfs_dirent *sd, 
static int kernfs_file_open(struct inode *inode, struct file *file)

{

	struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;

	struct kobject *kobj = attr_sd->s_parent->priv;

	const struct kernfs_ops *ops;

	struct sysfs_open_file *of;

	bool has_read, has_write, has_mmap;

	int error = -EACCES;



	/* need attr_sd for attr and ops, its parent for kobj */

	if (!sysfs_get_active(attr_sd))

		return -ENODEV;



	if (sysfs_is_bin(attr_sd)) {

		struct bin_attribute *battr = attr_sd->priv;



		has_read = battr->read || battr->mmap;

		has_write = battr->write || battr->mmap;

		has_mmap = battr->mmap;

	} else {

		const struct sysfs_ops *ops = sysfs_file_ops(attr_sd);

	ops = kernfs_ops(attr_sd);



		/* every kobject with an attribute needs a ktype assigned */

		if (WARN(!ops, KERN_ERR

			 "missing sysfs attribute operations for kobject: %s\n",

			 kobject_name(kobj)))

			goto err_out;



		has_read = ops->show;

		has_write = ops->store;

		has_mmap = false;

	}

	has_read = ops->seq_show || ops->read || ops->mmap;

	has_write = ops->write || ops->mmap;

	has_mmap = ops->mmap;



	/* check perms and supported operations */

	if ((file->f_mode & FMODE_WRITE) &&
@@ -729,10 +734,10 @@ static int kernfs_file_open(struct inode *inode, struct file *file) 
	 * seq_file or is not requested.  This unifies private data access

	 * and readable regular files are the vast majority anyway.

	 */

	if (sysfs_is_bin(attr_sd))

		error = seq_open(file, NULL);

	else

	if (ops->seq_show)

		error = seq_open(file, &kernfs_seq_ops);

	else

		error = seq_open(file, NULL);

	if (error)

		goto err_free;
@@ -777,7 +782,7 @@ void sysfs_unmap_bin_file(struct sysfs_dirent *sd) 
	struct sysfs_open_dirent *od;

	struct sysfs_open_file *of;



	if (!sysfs_is_bin(sd))

	if (!(sd->s_flags & SYSFS_FLAG_HAS_MMAP))

		return;



	spin_lock_irq(&sysfs_open_dirent_lock);
@@ -880,23 +885,96 @@ const struct file_operations kernfs_file_operations = { 
	.poll		= kernfs_file_poll,

};



static const struct kernfs_ops sysfs_file_kfops_empty = {

};



static const struct kernfs_ops sysfs_file_kfops_ro = {

	.seq_show	= sysfs_kf_seq_show,

};



static const struct kernfs_ops sysfs_file_kfops_wo = {

	.write		= sysfs_kf_write,

};



static const struct kernfs_ops sysfs_file_kfops_rw = {

	.seq_show	= sysfs_kf_seq_show,

	.write		= sysfs_kf_write,

};



static const struct kernfs_ops sysfs_bin_kfops_ro = {

	.read		= sysfs_kf_bin_read,

};



static const struct kernfs_ops sysfs_bin_kfops_wo = {

	.write		= sysfs_kf_bin_write,

};



static const struct kernfs_ops sysfs_bin_kfops_rw = {

	.read		= sysfs_kf_bin_read,

	.write		= sysfs_kf_bin_write,

	.mmap		= sysfs_kf_bin_mmap,

};



int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,

			   const struct attribute *attr, int type,

			   umode_t amode, const void *ns)

{

	umode_t mode = (amode & S_IALLUGO) | S_IFREG;

	const struct kernfs_ops *ops;

	struct sysfs_addrm_cxt acxt;

	struct sysfs_dirent *sd;

	int rc;



	if (type == SYSFS_KOBJ_ATTR) {

		struct kobject *kobj = dir_sd->priv;

		const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;



		/* every kobject with an attribute needs a ktype assigned */

		if (WARN(!sysfs_ops, KERN_ERR

			 "missing sysfs attribute operations for kobject: %s\n",

			 kobject_name(kobj)))

			return -EINVAL;



		if (sysfs_ops->show && sysfs_ops->store)

			ops = &sysfs_file_kfops_rw;

		else if (sysfs_ops->show)

			ops = &sysfs_file_kfops_ro;

		else if (sysfs_ops->store)

			ops = &sysfs_file_kfops_wo;

		else

			ops = &sysfs_file_kfops_empty;

	} else {

		struct bin_attribute *battr = (void *)attr;



		if ((battr->read && battr->write) || battr->mmap)

			ops = &sysfs_bin_kfops_rw;

		else if (battr->read)

			ops = &sysfs_bin_kfops_ro;

		else if (battr->write)

			ops = &sysfs_bin_kfops_wo;

		else

			ops = &sysfs_file_kfops_empty;

	}



	sd = sysfs_new_dirent(attr->name, mode, type);

	if (!sd)

		return -ENOMEM;



	sd->s_attr.ops = ops;

	sd->s_ns = ns;

	sd->priv = (void *)attr;

	sysfs_dirent_init_lockdep(sd);



	/*

	 * sd->s_attr.ops is accesible only while holding active ref.  We

	 * need to know whether some ops are implemented outside active

	 * ref.  Cache their existence in flags.

	 */

	if (ops->seq_show)

		sd->s_flags |= SYSFS_FLAG_HAS_SEQ_SHOW;

	if (ops->mmap)

		sd->s_flags |= SYSFS_FLAG_HAS_MMAP;



	sysfs_addrm_start(&acxt);

	rc = sysfs_add_one(&acxt, sd, dir_sd);

	sysfs_addrm_finish(&acxt);

fs/sysfs/sysfs.h

+3 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ struct sysfs_elem_symlink { 
};



struct sysfs_elem_attr {

	const struct kernfs_ops	*ops;

	struct sysfs_open_dirent *open;

};
@@ -89,6 +90,8 @@ struct sysfs_dirent { 
#define SYSFS_FLAG_MASK			~SYSFS_TYPE_MASK

#define SYSFS_FLAG_NS			0x01000

#define SYSFS_FLAG_REMOVED		0x02000

#define SYSFS_FLAG_HAS_SEQ_SHOW		0x04000

#define SYSFS_FLAG_HAS_MMAP		0x08000



static inline unsigned int sysfs_type(struct sysfs_dirent *sd)

{

include/linux/kernfs.h

+26 −0
Original line number Diff line number Diff line
@@ -33,6 +33,32 @@ struct sysfs_open_file { 
	const struct vm_operations_struct *vm_ops;

};



struct kernfs_ops {

	/*

	 * Read is handled by either seq_file or raw_read().

	 *

	 * If seq_show() is present, seq_file path is active.  The behavior

	 * is equivalent to single_open().  @sf->private points to the

	 * associated sysfs_open_file.

	 *

	 * read() is bounced through kernel buffer and a read larger than

	 * PAGE_SIZE results in partial operation of PAGE_SIZE.

	 */

	int (*seq_show)(struct seq_file *sf, void *v);



	ssize_t (*read)(struct sysfs_open_file *of, char *buf, size_t bytes,

			loff_t off);



	/*

	 * write() is bounced through kernel buffer and a write larger than

	 * PAGE_SIZE results in partial operation of PAGE_SIZE.

	 */

	ssize_t (*write)(struct sysfs_open_file *of, char *buf, size_t bytes,

			 loff_t off);



	int (*mmap)(struct sysfs_open_file *of, struct vm_area_struct *vma);

};



#ifdef CONFIG_SYSFS



struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,