[2.6.6-mm3] sysfs-leaves-file.patch

[Maneesh Soni <maneesh@in.ibm.com>]

=> changes in version 0.6
  o Re-diffed for 2.6.6-mm3
  o Provided protection against vulneribility of parent going before 
    the sysfs file being removed in sysfs_hash_and_remove(). Now it uses 
    s_dentry field to check if the file dentry is vaild instead of doing a 
    lookup. A new routine sysfs_drop_dentry() is introduced for this purpose.

=> changes in version 0.5
  o Cahnges to accomodate latest sysfs changes basically using
    sysfs_get_kobject() while opening sysfs files.

=> changes in version 0.4
  o Made necessary changes for checking DCACHE_SYSFS_CONNECTED flag while
    opening the sysfs file in check_perm() and a few changes in variable names

=> changes in version 0.3
  o Nil, just re-diffed

=> changes in version 0.2
  o Nil, just re-diffed

=> Changes:
  o Removed the extra kobject_get from sysfs_release() 

=======================================================
o sysfs_create_file() will just link a new sysfs_dirent() structure representing
  the attribute file to the kobject's s_children list.

o in sysfs_create() we take extra ref. only for dentries corresponding to
  non-regular files or in other words pin only non-leaf dentries.



 fs/sysfs/file.c  |   65 ++++++++++++++++++++++++++---------------------------
 fs/sysfs/inode.c |   67 ++++++++++++++++++++++++++++++++++++-------------------
 2 files changed, 77 insertions(+), 55 deletions(-)

diff -puN fs/sysfs/file.c~sysfs-leaves-file fs/sysfs/file.c
--- linux-2.6.6-mm3/fs/sysfs/file.c~sysfs-leaves-file	2004-05-17 15:29:21.000000000 +0530
+++ linux-2.6.6-mm3-maneesh/fs/sysfs/file.c	2004-05-17 15:29:21.000000000 +0530
@@ -9,14 +9,6 @@
 
 #include "sysfs.h"
 
-static struct file_operations sysfs_file_operations;
-
-static int init_file(struct inode * inode)
-{
-	inode->i_size = PAGE_SIZE;
-	inode->i_fop = &sysfs_file_operations;
-	return 0;
-}
 
 #define to_subsys(k) container_of(k,struct subsystem,kset.kobj)
 #define to_sattr(a) container_of(a,struct subsys_attribute,attr)
@@ -77,8 +69,10 @@ struct sysfs_buffer {
  */
 static int fill_read_buffer(struct file * file, struct sysfs_buffer * buffer)
 {
-	struct attribute * attr = file->f_dentry->d_fsdata;
-	struct kobject * kobj = file->f_dentry->d_parent->d_fsdata;
+	struct sysfs_dirent * attr_sd = file->f_dentry->d_fsdata;
+	struct attribute * attr = attr_sd->s_element;
+	struct sysfs_dirent * kobj_sd = file->f_dentry->d_parent->d_fsdata;
+	struct kobject * kobj = kobj_sd->s_element;
 	struct sysfs_ops * ops = buffer->ops;
 	int ret = 0;
 	ssize_t count;
@@ -134,6 +128,9 @@ static int flush_read_buffer(struct sysf
  *	is in the file's ->d_fsdata. The target object is in the directory's
  *	->d_fsdata.
  *
+ *	It is safe to use ->d_parent->d_fsdata as both dentry and the kobject 
+ *	are pinned in ->open().
+ *	
  *	We call fill_read_buffer() to allocate and fill the buffer from the
  *	object's show() method exactly once (if the read is happening from
  *	the beginning of the file). That should fill the entire buffer with
@@ -198,8 +195,10 @@ fill_write_buffer(struct sysfs_buffer * 
 static int 
 flush_write_buffer(struct file * file, struct sysfs_buffer * buffer, size_t count)
 {
-	struct attribute * attr = file->f_dentry->d_fsdata;
-	struct kobject * kobj = file->f_dentry->d_parent->d_fsdata;
+	struct sysfs_dirent * attr_sd = file->f_dentry->d_fsdata;
+	struct attribute * attr = attr_sd->s_element;
+	struct sysfs_dirent * kobj_sd = file->f_dentry->d_parent->d_fsdata;
+	struct kobject * kobj = kobj_sd->s_element;
 	struct sysfs_ops * ops = buffer->ops;
 
 	return ops->store(kobj,attr,buffer->page,count);
@@ -239,7 +238,8 @@ sysfs_write_file(struct file *file, cons
 static int check_perm(struct inode * inode, struct file * file)
 {
 	struct kobject *kobj = sysfs_get_kobject(file->f_dentry->d_parent);
-	struct attribute * attr = file->f_dentry->d_fsdata;
+	struct sysfs_dirent * attr_sd = file->f_dentry->d_fsdata;
+	struct attribute * attr = attr_sd->s_element;
 	struct sysfs_buffer * buffer;
 	struct sysfs_ops * ops = NULL;
 	int error = 0;
@@ -320,8 +320,10 @@ static int sysfs_open_file(struct inode 
 
 static int sysfs_release(struct inode * inode, struct file * filp)
 {
-	struct kobject * kobj = filp->f_dentry->d_parent->d_fsdata;
-	struct attribute * attr = filp->f_dentry->d_fsdata;
+	struct sysfs_dirent * attr_sd = filp->f_dentry->d_fsdata;
+	struct attribute * attr = attr_sd->s_element;
+	struct sysfs_dirent * kobj_sd = filp->f_dentry->d_parent->d_fsdata;
+	struct kobject * kobj = kobj_sd->s_element;
 	struct sysfs_buffer * buffer = filp->private_data;
 
 	if (kobj) 
@@ -336,7 +338,7 @@ static int sysfs_release(struct inode * 
 	return 0;
 }
 
-static struct file_operations sysfs_file_operations = {
+struct file_operations sysfs_file_operations = {
 	.read		= sysfs_read_file,
 	.write		= sysfs_write_file,
 	.llseek		= generic_file_llseek,
@@ -345,23 +347,20 @@ static struct file_operations sysfs_file
 };
 
 
-int sysfs_add_file(struct dentry * dir, const struct attribute * attr)
+int sysfs_add_file(struct dentry * parent, const struct attribute * attr, int t)
 {
-	struct dentry * dentry;
-	int error;
+	struct sysfs_dirent * sd;
+	struct sysfs_dirent * parent_sd = parent->d_fsdata;
+	int error = 0;
 
-	down(&dir->d_inode->i_sem);
-	dentry = sysfs_get_dentry(dir,attr->name);
-	if (!IS_ERR(dentry)) {
-		error = sysfs_create(dentry,
-				     (attr->mode & S_IALLUGO) | S_IFREG,
-				     init_file);
-		if (!error)
-			dentry->d_fsdata = (void *)attr;
-		dput(dentry);
-	} else
-		error = PTR_ERR(dentry);
-	up(&dir->d_inode->i_sem);
+	down(&parent->d_inode->i_sem);			
+	sd = sysfs_new_dirent(parent_sd, (void *) attr, t);
+	if (!sd)
+		error =  -ENOMEM;
+	else
+		sd->s_mode =  (attr->mode & S_IALLUGO) | S_IFREG ;
+	up(&parent->d_inode->i_sem);			
+	
 	return error;
 }
 
@@ -374,8 +373,8 @@ int sysfs_add_file(struct dentry * dir, 
 
 int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 {
-	if (kobj && attr)
-		return sysfs_add_file(kobj->dentry,attr);
+	if (kobj && kobj->dentry && attr)
+		return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR);
 	return -EINVAL;
 }
 
diff -puN fs/sysfs/inode.c~sysfs-leaves-file fs/sysfs/inode.c
--- linux-2.6.6-mm3/fs/sysfs/inode.c~sysfs-leaves-file	2004-05-17 15:29:21.000000000 +0530
+++ linux-2.6.6-mm3-maneesh/fs/sysfs/inode.c	2004-05-17 15:54:30.000000000 +0530
@@ -11,6 +11,8 @@
 #include <linux/pagemap.h>
 #include <linux/namei.h>
 #include <linux/backing-dev.h>
+#include "sysfs.h"
+
 extern struct super_block * sysfs_sb;
 
 static struct address_space_operations sysfs_aops = {
@@ -61,7 +63,8 @@ int sysfs_create(struct dentry * dentry,
 		error = init(inode);
 	if (!error) {
 		d_instantiate(dentry, inode);
-		dget(dentry); /* Extra count - pin the dentry in core */
+		if (S_ISDIR(mode)) 
+			dget(dentry);  /* pin only directory dentry in core */
 	} else
 		iput(inode);
  Done:
@@ -83,31 +86,51 @@ struct dentry * sysfs_get_dentry(struct 
 	return lookup_hash(&qstr,parent);
 }
 
+static struct sysfs_dirent * sysfs_find_dirent(struct sysfs_dirent * parent_sd, 
+					  const char * name)
+{
+	struct sysfs_dirent *sd;
+
+	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+			if (sd->s_element) {
+				if (!strcmp(sysfs_get_name(sd), name)) 
+					return sd;
+			}
+	} 
+	return NULL;
+}
+
+/* Unhashes the dentry corresponding to given sysfs_dirent 
+ * Called with parent inode's i_sem held.
+ */
+void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
+{
+	struct dentry * dentry = sd->s_dentry;
+
+	if (dentry) {
+		spin_lock(&dcache_lock);
+		dget_locked(dentry);
+		if (!(d_unhashed(dentry) && dentry->d_inode)) {
+			__d_drop(dentry);
+			spin_unlock(&dcache_lock);
+			simple_unlink(parent->d_inode, dentry);
+		} else {
+			spin_unlock(&dcache_lock);
+			dput(dentry);
+		}
+	}
+}
+
 void sysfs_hash_and_remove(struct dentry * dir, const char * name)
 {
-	struct dentry * victim;
+	struct sysfs_dirent * sd;
 
 	down(&dir->d_inode->i_sem);
-	victim = sysfs_get_dentry(dir,name);
-	if (!IS_ERR(victim)) {
-		/* make sure dentry is really there */
-		if (victim->d_inode && 
-		    (victim->d_parent->d_inode == dir->d_inode)) {
-			pr_debug("sysfs: Removing %s (%d)\n", victim->d_name.name,
-				 atomic_read(&victim->d_count));
-
-			d_drop(victim);
-			/* release the target kobject in case of 
-			 * a symlink
-			 */
-			if (S_ISLNK(victim->d_inode->i_mode))
-				kobject_put(victim->d_fsdata);
-			simple_unlink(dir->d_inode,victim);
-		}
-		/*
-		 * Drop reference from sysfs_get_dentry() above.
-		 */
-		dput(victim);
+	sd = sysfs_find_dirent(dir->d_fsdata, name);
+	if (sd) {
+		list_del_init(&sd->s_sibling);
+		sysfs_drop_dentry(sd, dir);
+		sysfs_put(sd);
 	}
 	up(&dir->d_inode->i_sem);
 }

_
-- 
Maneesh Soni
Linux Technology Center, 
IBM Software Lab, Bangalore, India
email: maneesh@in.ibm.com
Phone: 91-80-25044999 Fax: 91-80-25268553
T/L : 9243696