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: Tejun Heo <tj@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo
Greg Kroah-Hartman
parent
93b2b8e4aa
commit
c2b19daf67
1 changed files with 126 additions and 65 deletions
191
fs/sysfs/file.c
191
fs/sysfs/file.c
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@ -86,13 +86,13 @@ static const struct sysfs_ops *sysfs_file_ops(struct sysfs_dirent *sd)
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* details like buffering and seeking. The following function pipes
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* sysfs_ops->show() result through seq_file.
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*/
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static int sysfs_seq_show(struct seq_file *sf, void *v)
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static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
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{
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struct sysfs_open_file *of = sf->private;
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struct kobject *kobj = of->sd->s_parent->priv;
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const struct sysfs_ops *ops;
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char *buf;
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const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
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ssize_t count;
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char *buf;
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/* acquire buffer and ensure that it's >= PAGE_SIZE */
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count = seq_get_buf(sf, &buf);
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@ -102,33 +102,14 @@ static int sysfs_seq_show(struct seq_file *sf, void *v)
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}
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/*
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* Need @of->sd for attr and ops, its parent for kobj. @of->mutex
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* nests outside active ref and is just to ensure that the ops
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* aren't called concurrently for the same open file.
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* Invoke show(). Control may reach here via seq file lseek even
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* if @ops->show() isn't implemented.
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*/
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mutex_lock(&of->mutex);
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if (!sysfs_get_active(of->sd)) {
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mutex_unlock(&of->mutex);
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return -ENODEV;
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}
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of->event = atomic_read(&of->sd->s_attr.open->event);
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/*
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* Lookup @ops and invoke show(). Control may reach here via seq
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* file lseek even if @ops->show() isn't implemented.
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*/
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ops = sysfs_file_ops(of->sd);
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if (ops->show)
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if (ops->show) {
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count = ops->show(kobj, of->sd->priv, buf);
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else
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count = 0;
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sysfs_put_active(of->sd);
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mutex_unlock(&of->mutex);
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if (count < 0)
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return count;
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if (count < 0)
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return count;
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}
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/*
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* The code works fine with PAGE_SIZE return but it's likely to
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@ -144,68 +125,146 @@ static int sysfs_seq_show(struct seq_file *sf, void *v)
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return 0;
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}
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/*
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* Read method for bin files. As reading a bin file can have side-effects,
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* the exact offset and bytes specified in read(2) call should be passed to
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* the read callback making it difficult to use seq_file. Implement
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* simplistic custom buffering for bin files.
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*/
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static ssize_t sysfs_bin_read(struct file *file, char __user *userbuf,
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size_t bytes, loff_t *off)
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static ssize_t sysfs_kf_bin_read(struct sysfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct sysfs_open_file *of = sysfs_of(file);
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struct bin_attribute *battr = of->sd->priv;
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struct kobject *kobj = of->sd->s_parent->priv;
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loff_t size = file_inode(file)->i_size;
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int count = min_t(size_t, bytes, PAGE_SIZE);
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loff_t offs = *off;
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char *buf;
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loff_t size = file_inode(of->file)->i_size;
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if (!bytes)
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if (!count)
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return 0;
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if (size) {
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if (offs > size)
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if (pos > size)
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return 0;
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if (offs + count > size)
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count = size - offs;
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if (pos + count > size)
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count = size - pos;
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}
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buf = kmalloc(count, GFP_KERNEL);
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if (!battr->read)
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return -EIO;
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return battr->read(of->file, kobj, battr, buf, pos, count);
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}
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static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
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{
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struct sysfs_open_file *of = sf->private;
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/*
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* @of->mutex nests outside active ref and is just to ensure that
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* the ops aren't called concurrently for the same open file.
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*/
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mutex_lock(&of->mutex);
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if (!sysfs_get_active(of->sd))
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return ERR_PTR(-ENODEV);
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/*
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* The same behavior and code as single_open(). Returns !NULL if
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* pos is at the beginning; otherwise, NULL.
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*/
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return NULL + !*ppos;
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}
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static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
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{
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/*
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* The same behavior and code as single_open(), always terminate
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* after the initial read.
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*/
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++*ppos;
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return NULL;
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}
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static void kernfs_seq_stop(struct seq_file *sf, void *v)
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{
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struct sysfs_open_file *of = sf->private;
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sysfs_put_active(of->sd);
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mutex_unlock(&of->mutex);
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}
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static int kernfs_seq_show(struct seq_file *sf, void *v)
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{
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struct sysfs_open_file *of = sf->private;
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of->event = atomic_read(&of->sd->s_attr.open->event);
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return sysfs_kf_seq_show(sf, v);
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}
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static const struct seq_operations kernfs_seq_ops = {
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.start = kernfs_seq_start,
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.next = kernfs_seq_next,
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.stop = kernfs_seq_stop,
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.show = kernfs_seq_show,
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};
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/*
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* As reading a bin file can have side-effects, the exact offset and bytes
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* specified in read(2) call should be passed to the read callback making
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* it difficult to use seq_file. Implement simplistic custom buffering for
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* bin files.
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*/
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static ssize_t kernfs_file_direct_read(struct sysfs_open_file *of,
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char __user *user_buf, size_t count,
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loff_t *ppos)
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{
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ssize_t len = min_t(size_t, count, PAGE_SIZE);
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char *buf;
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buf = kmalloc(len, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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/* need of->sd for battr, its parent for kobj */
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/*
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* @of->mutex nests outside active ref and is just to ensure that
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* the ops aren't called concurrently for the same open file.
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*/
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mutex_lock(&of->mutex);
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if (!sysfs_get_active(of->sd)) {
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count = -ENODEV;
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len = -ENODEV;
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mutex_unlock(&of->mutex);
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goto out_free;
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}
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if (battr->read)
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count = battr->read(file, kobj, battr, buf, offs, count);
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else
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count = -EIO;
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len = sysfs_kf_bin_read(of, buf, len, *ppos);
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sysfs_put_active(of->sd);
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mutex_unlock(&of->mutex);
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if (count < 0)
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if (len < 0)
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goto out_free;
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if (copy_to_user(userbuf, buf, count)) {
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count = -EFAULT;
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if (copy_to_user(user_buf, buf, len)) {
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len = -EFAULT;
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goto out_free;
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}
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pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
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*off = offs + count;
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*ppos += len;
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out_free:
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kfree(buf);
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return count;
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return len;
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}
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/**
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* kernfs_file_read - kernfs vfs read callback
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* @file: file pointer
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* @user_buf: data to write
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* @count: number of bytes
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* @ppos: starting offset
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*/
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static ssize_t kernfs_file_read(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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struct sysfs_open_file *of = sysfs_of(file);
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if (sysfs_is_bin(of->sd))
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return kernfs_file_direct_read(of, user_buf, count, ppos);
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else
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return seq_read(file, user_buf, count, ppos);
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}
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/**
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@ -677,12 +736,14 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
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* and readable regular files are the vast majority anyway.
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*/
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if (sysfs_is_bin(attr_sd))
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error = single_open(file, NULL, of);
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error = seq_open(file, NULL);
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else
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error = single_open(file, sysfs_seq_show, of);
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error = seq_open(file, &kernfs_seq_ops);
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if (error)
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goto err_free;
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((struct seq_file *)file->private_data)->private = of;
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/* seq_file clears PWRITE unconditionally, restore it if WRITE */
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if (file->f_mode & FMODE_WRITE)
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file->f_mode |= FMODE_PWRITE;
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@ -697,7 +758,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
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return 0;
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err_close:
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single_release(inode, file);
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seq_release(inode, file);
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err_free:
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kfree(of);
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err_out:
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@ -711,7 +772,7 @@ static int sysfs_release(struct inode *inode, struct file *filp)
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struct sysfs_open_file *of = sysfs_of(filp);
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sysfs_put_open_dirent(sd, of);
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single_release(inode, filp);
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seq_release(inode, filp);
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kfree(of);
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return 0;
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@ -816,7 +877,7 @@ void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
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EXPORT_SYMBOL_GPL(sysfs_notify);
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const struct file_operations sysfs_file_operations = {
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.read = seq_read,
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.read = kernfs_file_read,
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.write = sysfs_write_file,
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.llseek = generic_file_llseek,
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.open = sysfs_open_file,
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@ -825,7 +886,7 @@ const struct file_operations sysfs_file_operations = {
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};
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const struct file_operations sysfs_bin_operations = {
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.read = sysfs_bin_read,
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.read = kernfs_file_read,
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.write = sysfs_write_file,
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.llseek = generic_file_llseek,
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.mmap = sysfs_bin_mmap,
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