[PATCH RFC 14/20] proc: store cookie in private data

[Christian Brauner <brauner@kernel.org>]

Store the cookie to detect concurrent seeks on directories in
file->private_data.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/proc/base.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 72a1acd03675..8a8aab6b9801 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3870,12 +3870,12 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
 	if (!dir_emit_dots(file, ctx))
 		return 0;
 
-	/* f_version caches the tgid value that the last readdir call couldn't
-	 * return. lseek aka telldir automagically resets f_version to 0.
+	/* We cache the tgid value that the last readdir call couldn't
+	 * return and lseek resets it to 0.
 	 */
 	ns = proc_pid_ns(inode->i_sb);
-	tid = (int)file->f_version;
-	file->f_version = 0;
+	tid = (int)(intptr_t)file->private_data;
+	file->private_data = NULL;
 	for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
 	     task;
 	     task = next_tid(task), ctx->pos++) {
@@ -3890,7 +3890,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
 				proc_task_instantiate, task, NULL)) {
 			/* returning this tgid failed, save it as the first
 			 * pid for the next readir call */
-			file->f_version = (u64)tid;
+			file->private_data = (void *)(intptr_t)tid;
 			put_task_struct(task);
 			break;
 		}
@@ -3915,6 +3915,12 @@ static int proc_task_getattr(struct mnt_idmap *idmap,
 	return 0;
 }
 
+static loff_t proc_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	return generic_llseek_cookie(file, offset, whence,
+				     (u64 *)(uintptr_t)&file->private_data);
+}
+
 static const struct inode_operations proc_task_inode_operations = {
 	.lookup		= proc_task_lookup,
 	.getattr	= proc_task_getattr,
@@ -3925,7 +3931,7 @@ static const struct inode_operations proc_task_inode_operations = {
 static const struct file_operations proc_task_operations = {
 	.read		= generic_read_dir,
 	.iterate_shared	= proc_task_readdir,
-	.llseek		= generic_file_llseek,
+	.llseek		= proc_dir_llseek,
 };
 
 void __init set_proc_pid_nlink(void)

-- 
2.45.2