linux-kernel - [PATCH] proc: mandate ->proc_lseek in "struct proc

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Date:   Sat, 20 Mar 2021 18:42:08 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH] proc: mandate ->proc_lseek in "struct proc_ops"

Now that proc_ops are separate from file_operations and other
operations it easy to check all instances to have ->proc_lseek
hook and remove check in main code.

Note:
nonseekable_open() files naturally don't require ->proc_lseek.

Garbage collect pde_lseek() function.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 drivers/isdn/capi/kcapi_proc.c                     |    1 +
 drivers/net/wireless/intersil/hostap/hostap_proc.c |    1 +
 drivers/scsi/esas2r/esas2r_main.c                  |    1 +
 fs/proc/inode.c                                    |   14 ++------------
 include/linux/proc_fs.h                            |    1 +
 5 files changed, 6 insertions(+), 12 deletions(-)

--- a/drivers/isdn/capi/kcapi_proc.c
+++ b/drivers/isdn/capi/kcapi_proc.c
@@ -201,6 +201,7 @@ static ssize_t empty_read(struct file *file, char __user *buf,
 
 static const struct proc_ops empty_proc_ops = {
 	.proc_read	= empty_read,
+	.proc_lseek	= default_llseek,
 };
 
 // ---------------------------------------------------------------------------
--- a/drivers/net/wireless/intersil/hostap/hostap_proc.c
+++ b/drivers/net/wireless/intersil/hostap/hostap_proc.c
@@ -227,6 +227,7 @@ static ssize_t prism2_aux_dump_proc_no_read(struct file *file, char __user *buf,
 
 static const struct proc_ops prism2_aux_dump_proc_ops = {
 	.proc_read	= prism2_aux_dump_proc_no_read,
+	.proc_lseek	= default_llseek,
 };
 
 
--- a/drivers/scsi/esas2r/esas2r_main.c
+++ b/drivers/scsi/esas2r/esas2r_main.c
@@ -617,6 +617,7 @@ static const struct file_operations esas2r_proc_fops = {
 };
 
 static const struct proc_ops esas2r_proc_ops = {
+	.proc_lseek		= default_llseek,
 	.proc_ioctl		= esas2r_proc_ioctl,
 #ifdef CONFIG_COMPAT
 	.proc_compat_ioctl	= compat_ptr_ioctl,
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -273,25 +273,15 @@ void proc_entry_rundown(struct proc_dir_entry *de)
 	spin_unlock(&de->pde_unload_lock);
 }
 
-static loff_t pde_lseek(struct proc_dir_entry *pde, struct file *file, loff_t offset, int whence)
-{
-	typeof_member(struct proc_ops, proc_lseek) lseek;
-
-	lseek = pde->proc_ops->proc_lseek;
-	if (!lseek)
-		lseek = default_llseek;
-	return lseek(file, offset, whence);
-}
-
 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct proc_dir_entry *pde = PDE(file_inode(file));
 	loff_t rv = -EINVAL;
 
 	if (pde_is_permanent(pde)) {
-		return pde_lseek(pde, file, offset, whence);
+		return pde->proc_ops->proc_lseek(file, offset, whence);
 	} else if (use_pde(pde)) {
-		rv = pde_lseek(pde, file, offset, whence);
+		rv = pde->proc_ops->proc_lseek(file, offset, whence);
 		unuse_pde(pde);
 	}
 	return rv;
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -32,6 +32,7 @@ struct proc_ops {
 	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 *);
+	/* mandatory unless nonseekable_open() or equivalent is used */
 	loff_t	(*proc_lseek)(struct file *, loff_t, int);
 	int	(*proc_release)(struct inode *, struct file *);
 	__poll_t (*proc_poll)(struct file *, struct poll_table_struct *);