sysfs: implement bin_buffer

Implement bin_buffer which contains a mutex and pointer to PAGE_SIZE
buffer to properly synchronize accesses to per-openfile buffer and
prepare for immediate-kobj-disconnect.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 49 insertions, 15 deletions

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 67a0d5030c9..5dc47fe5de5 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -20,6 +20,11 @@
 
 #include "sysfs.h"
 
+struct bin_buffer {
+        struct mutex    mutex;
+        void            *buffer;
+};
+
 static int
 fill_read(struct dentry *dentry, char *buffer, loff_t off, size_t count)
 {
@@ -36,7 +41,7 @@ fill_read(struct dentry *dentry, char *buffer, loff_t off, size_t count)
 static ssize_t
 read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
 {
-        char *buffer = file->private_data;
+        struct bin_buffer *bb = file->private_data;
         struct dentry *dentry = file->f_path.dentry;
         int size = dentry->d_inode->i_size;
         loff_t offs = *off;
@@ -49,17 +54,23 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
                         count = size - offs;
         }
 
-        count = fill_read(dentry, buffer, offs, count);
+        mutex_lock(&bb->mutex);
+
+        count = fill_read(dentry, bb->buffer, offs, count);
         if (count < 0)
-                return count;
+                goto out_unlock;
 
-        if (copy_to_user(userbuf, buffer, count))
-                return -EFAULT;
+        if (copy_to_user(userbuf, bb->buffer, count)) {
+                count = -EFAULT;
+                goto out_unlock;
+        }
 
         pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
 
         *off = offs + count;
 
+ out_unlock:
+        mutex_unlock(&bb->mutex);
         return count;
 }
 
@@ -79,7 +90,7 @@ flush_write(struct dentry *dentry, char *buffer, loff_t offset, size_t count)
 static ssize_t write(struct file *file, const char __user *userbuf,
                      size_t bytes, loff_t *off)
 {
-        char *buffer = file->private_data;
+        struct bin_buffer *bb = file->private_data;
         struct dentry *dentry = file->f_path.dentry;
         int size = dentry->d_inode->i_size;
         loff_t offs = *off;
@@ -92,25 +103,38 @@ static ssize_t write(struct file *file, const char __user *userbuf,
                         count = size - offs;
         }
 
-        if (copy_from_user(buffer, userbuf, count))
-                return -EFAULT;
+        mutex_lock(&bb->mutex);
+
+        if (copy_from_user(bb->buffer, userbuf, count)) {
+                count = -EFAULT;
+                goto out_unlock;
+        }
 
-        count = flush_write(dentry, buffer, offs, count);
+        count = flush_write(dentry, bb->buffer, offs, count);
         if (count > 0)
                 *off = offs + count;
+
+ out_unlock:
+        mutex_unlock(&bb->mutex);
         return count;
 }
 
 static int mmap(struct file *file, struct vm_area_struct *vma)
 {
+        struct bin_buffer *bb = file->private_data;
         struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
         struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
         struct kobject *kobj = to_kobj(file->f_path.dentry->d_parent);
+        int rc;
 
         if (!attr->mmap)
                 return -EINVAL;
 
-        return attr->mmap(kobj, attr, vma);
+        mutex_lock(&bb->mutex);
+        rc = attr->mmap(kobj, attr, vma);
+        mutex_unlock(&bb->mutex);
+
+        return rc;
 }
 
 static int open(struct inode * inode, struct file * file)
@@ -118,6 +142,7 @@ static int open(struct inode * inode, struct file * file)
         struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
         struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
         struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
+        struct bin_buffer *bb = NULL;
         int error = -EINVAL;
 
         if (!kobj || !attr)
@@ -135,14 +160,22 @@ static int open(struct inode * inode, struct file * file)
                 goto Error;
 
         error = -ENOMEM;
-        file->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
-        if (!file->private_data)
+        bb = kzalloc(sizeof(*bb), GFP_KERNEL);
+        if (!bb)
                 goto Error;
 
+        bb->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!bb->buffer)
+                goto Error;
+
+        mutex_init(&bb->mutex);
+        file->private_data = bb;
+
         error = 0;
-    goto Done;
+        goto Done;
 
  Error:
+        kfree(bb);
         module_put(attr->attr.owner);
  Done:
         if (error)
@@ -155,11 +188,12 @@ static int release(struct inode * inode, struct file * file)
         struct kobject * kobj = to_kobj(file->f_path.dentry->d_parent);
         struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
         struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
-        u8 * buffer = file->private_data;
+        struct bin_buffer *bb = file->private_data;
 
         kobject_put(kobj);
         module_put(attr->attr.owner);
-        kfree(buffer);
+        kfree(bb->buffer);
+        kfree(bb);
         return 0;
 }