[PATCH 17/23] proc: add a read_iter method to proc proc_ops

[Christoph Hellwig]

This will allow proc files to implement iter read semantics.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 fs/proc/inode.c         | 28 ++++++++++++++++++++++++++++
 include/linux/proc_fs.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 28d6105e908e4c..fa86619cebc2be 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -297,6 +297,29 @@ static loff_t proc_reg_llseek(struct file *file, loff_t 
offset, int whence)
        return rv;
 }
 
+static ssize_t pde_read_iter(struct proc_dir_entry *pde, struct kiocb *iocb,
+               struct iov_iter *iter)
+{
+       if (!pde->proc_ops->proc_read_iter)
+               return -EINVAL;
+       return pde->proc_ops->proc_read_iter(iocb, iter);
+}
+
+static ssize_t proc_reg_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+       struct proc_dir_entry *pde = PDE(file_inode(iocb->ki_filp));
+       ssize_t ret;
+
+       if (pde_is_permanent(pde))
+               return pde_read_iter(pde, iocb, iter);
+
+       if (!use_pde(pde))
+               return -EIO;
+       ret = pde_read_iter(pde, iocb, iter);
+       unuse_pde(pde);
+       return ret;
+}
+
 static ssize_t pde_read(struct proc_dir_entry *pde, struct file *file, char 
__user *buf, size_t count, loff_t *ppos)
 {
        typeof_member(struct proc_ops, proc_read) read;
@@ -312,6 +335,9 @@ static ssize_t proc_reg_read(struct file *file, char __user 
*buf, size_t count,
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;
 
+       if (pde->proc_ops->proc_read_iter)
+               return iter_read(file, buf, count, ppos, proc_reg_read_iter);
+
        if (pde_is_permanent(pde)) {
                return pde_read(pde, file, buf, count, ppos);
        } else if (use_pde(pde)) {
@@ -569,6 +595,7 @@ static int proc_reg_release(struct inode *inode, struct 
file *file)
 static const struct file_operations proc_reg_file_ops = {
        .llseek         = proc_reg_llseek,
        .read           = proc_reg_read,
+       .read_iter      = proc_reg_read_iter,
        .write          = proc_reg_write,
        .poll           = proc_reg_poll,
        .unlocked_ioctl = proc_reg_unlocked_ioctl,
@@ -585,6 +612,7 @@ static const struct file_operations proc_reg_file_ops = {
 static const struct file_operations proc_reg_file_ops_no_compat = {
        .llseek         = proc_reg_llseek,
        .read           = proc_reg_read,
+       .read_iter      = proc_reg_read_iter,
        .write          = proc_reg_write,
        .poll           = proc_reg_poll,
        .unlocked_ioctl = proc_reg_unlocked_ioctl,
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index d1eed1b4365172..97b3f5f06db9d8 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -30,6 +30,7 @@ struct proc_ops {
        unsigned int proc_flags;
        int     (*proc_open)(struct inode *, struct file *);
        ssize_t (*proc_read)(struct file *, char __user *, size_t, loff_t *);
+       ssize_t (*proc_read_iter)(struct kiocb *, struct iov_iter *);
        ssize_t (*proc_write)(struct file *, const char __user *, size_t, 
loff_t *);
        loff_t  (*proc_lseek)(struct file *, loff_t, int);
        int     (*proc_release)(struct inode *, struct file *);
-- 
2.26.2