Commit c2b19daf authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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sysfs, kernfs: prepare read path for kernfs



We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly.  This patch
rearranges read path so that the kernfs and sysfs parts are separate.

* Regular file read path is refactored such that
  kernfs_seq_start/next/stop/show() handle all the boilerplate work
  including locking and updating event count for poll, while
  sysfs_kf_seq_show() deals with interaction with kobj show method.

* Bin file read path is refactored such that kernfs_file_direct_read()
  handles all the boilerplate work including buffer management and
  locking, while sysfs_kf_bin_read() deals with interaction with
  bin_attribute read method.

kernfs_file_read() is added.  It invokes either the seq_file or direct
read path depending on the file type.  This will eventually allow
using the same file_operations for both file types, which is necessary
to separate out kernfs.

While this patch changes the order of some operations, it shouldn't
change any visible behavior.

v2: Dropped unnecessary zeroing of @count from sysfs_kf_seq_show().
    Add comments explaining single_open() behavior.  Both suggested by
    Pavel.

v3: seq_stop() is called even after seq_start() failed.
    kernfs_seq_start() updated so that it doesn't unlock
    sysfs_open_file->mutex on failure so that kernfs_seq_stop()
    doesn't try to unlock an already unlocked mutex.  Reported by
    Fengguang.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 93b2b8e4
......@@ -86,13 +86,13 @@ static const struct sysfs_ops *sysfs_file_ops(struct sysfs_dirent *sd)
* details like buffering and seeking. The following function pipes
* sysfs_ops->show() result through seq_file.
*/
static int sysfs_seq_show(struct seq_file *sf, void *v)
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{
struct sysfs_open_file *of = sf->private;
struct kobject *kobj = of->sd->s_parent->priv;
const struct sysfs_ops *ops;
char *buf;
const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
ssize_t count;
char *buf;
/* acquire buffer and ensure that it's >= PAGE_SIZE */
count = seq_get_buf(sf, &buf);
......@@ -102,33 +102,14 @@ static int sysfs_seq_show(struct seq_file *sf, void *v)
}
/*
* Need @of->sd for attr and ops, its parent for kobj. @of->mutex
* nests outside active ref and is just to ensure that the ops
* aren't called concurrently for the same open file.
* Invoke show(). Control may reach here via seq file lseek even
* if @ops->show() isn't implemented.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
mutex_unlock(&of->mutex);
return -ENODEV;
}
of->event = atomic_read(&of->sd->s_attr.open->event);
/*
* Lookup @ops and invoke show(). Control may reach here via seq
* file lseek even if @ops->show() isn't implemented.
*/
ops = sysfs_file_ops(of->sd);
if (ops->show)
if (ops->show) {
count = ops->show(kobj, of->sd->priv, buf);
else
count = 0;
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
if (count < 0)
return count;
if (count < 0)
return count;
}
/*
* The code works fine with PAGE_SIZE return but it's likely to
......@@ -144,68 +125,146 @@ static int sysfs_seq_show(struct seq_file *sf, void *v)
return 0;
}
/*
* Read method for bin files. As reading a bin file can have side-effects,
* the exact offset and bytes specified in read(2) call should be passed to
* the read callback making it difficult to use seq_file. Implement
* simplistic custom buffering for bin files.
*/
static ssize_t sysfs_bin_read(struct file *file, char __user *userbuf,
size_t bytes, loff_t *off)
static ssize_t sysfs_kf_bin_read(struct sysfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
struct sysfs_open_file *of = sysfs_of(file);
struct bin_attribute *battr = of->sd->priv;
struct kobject *kobj = of->sd->s_parent->priv;
loff_t size = file_inode(file)->i_size;
int count = min_t(size_t, bytes, PAGE_SIZE);
loff_t offs = *off;
char *buf;
loff_t size = file_inode(of->file)->i_size;
if (!bytes)
if (!count)
return 0;
if (size) {
if (offs > size)
if (pos > size)
return 0;
if (offs + count > size)
count = size - offs;
if (pos + count > size)
count = size - pos;
}
buf = kmalloc(count, GFP_KERNEL);
if (!battr->read)
return -EIO;
return battr->read(of->file, kobj, battr, buf, pos, count);
}
static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
{
struct sysfs_open_file *of = sf->private;
/*
* @of->mutex nests outside active ref and is just to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd))
return ERR_PTR(-ENODEV);
/*
* The same behavior and code as single_open(). Returns !NULL if
* pos is at the beginning; otherwise, NULL.
*/
return NULL + !*ppos;
}
static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
{
/*
* The same behavior and code as single_open(), always terminate
* after the initial read.
*/
++*ppos;
return NULL;
}
static void kernfs_seq_stop(struct seq_file *sf, void *v)
{
struct sysfs_open_file *of = sf->private;
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
}
static int kernfs_seq_show(struct seq_file *sf, void *v)
{
struct sysfs_open_file *of = sf->private;
of->event = atomic_read(&of->sd->s_attr.open->event);
return sysfs_kf_seq_show(sf, v);
}
static const struct seq_operations kernfs_seq_ops = {
.start = kernfs_seq_start,
.next = kernfs_seq_next,
.stop = kernfs_seq_stop,
.show = kernfs_seq_show,
};
/*
* As reading a bin file can have side-effects, the exact offset and bytes
* specified in read(2) call should be passed to the read callback making
* it difficult to use seq_file. Implement simplistic custom buffering for
* bin files.
*/
static ssize_t kernfs_file_direct_read(struct sysfs_open_file *of,
char __user *user_buf, size_t count,
loff_t *ppos)
{
ssize_t len = min_t(size_t, count, PAGE_SIZE);
char *buf;
buf = kmalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/* need of->sd for battr, its parent for kobj */
/*
* @of->mutex nests outside active ref and is just to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
count = -ENODEV;
len = -ENODEV;
mutex_unlock(&of->mutex);
goto out_free;
}
if (battr->read)
count = battr->read(file, kobj, battr, buf, offs, count);
else
count = -EIO;
len = sysfs_kf_bin_read(of, buf, len, *ppos);
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
if (count < 0)
if (len < 0)
goto out_free;
if (copy_to_user(userbuf, buf, count)) {
count = -EFAULT;
if (copy_to_user(user_buf, buf, len)) {
len = -EFAULT;
goto out_free;
}
pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
*off = offs + count;
*ppos += len;
out_free:
kfree(buf);
return count;
return len;
}
/**
* kernfs_file_read - kernfs vfs read callback
* @file: file pointer
* @user_buf: data to write
* @count: number of bytes
* @ppos: starting offset
*/
static ssize_t kernfs_file_read(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
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
return seq_read(file, user_buf, count, ppos);
}
/**
......@@ -677,12 +736,14 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
* and readable regular files are the vast majority anyway.
*/
if (sysfs_is_bin(attr_sd))
error = single_open(file, NULL, of);
error = seq_open(file, NULL);
else
error = single_open(file, sysfs_seq_show, of);
error = seq_open(file, &kernfs_seq_ops);
if (error)
goto err_free;
((struct seq_file *)file->private_data)->private = of;
/* seq_file clears PWRITE unconditionally, restore it if WRITE */
if (file->f_mode & FMODE_WRITE)
file->f_mode |= FMODE_PWRITE;
......@@ -697,7 +758,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
return 0;
err_close:
single_release(inode, file);
seq_release(inode, file);
err_free:
kfree(of);
err_out:
......@@ -711,7 +772,7 @@ static int sysfs_release(struct inode *inode, struct file *filp)
struct sysfs_open_file *of = sysfs_of(filp);
sysfs_put_open_dirent(sd, of);
single_release(inode, filp);
seq_release(inode, filp);
kfree(of);
return 0;
......@@ -816,7 +877,7 @@ void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
EXPORT_SYMBOL_GPL(sysfs_notify);
const struct file_operations sysfs_file_operations = {
.read = seq_read,
.read = kernfs_file_read,
.write = sysfs_write_file,
.llseek = generic_file_llseek,
.open = sysfs_open_file,
......@@ -825,7 +886,7 @@ const struct file_operations sysfs_file_operations = {
};
const struct file_operations sysfs_bin_operations = {
.read = sysfs_bin_read,
.read = kernfs_file_read,
.write = sysfs_write_file,
.llseek = generic_file_llseek,
.mmap = sysfs_bin_mmap,
......
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