Re: LXC broken with 5.10-stable?, ok with 5.9-stable (Re: Linux 5.10.3)

[Linus Torvalds <torvalds@linux-foundation.org>]

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On Sun, Dec 27, 2020 at 10:39 AM Jussi Kivilinna <jussi.kivilinna@iki.fi> wrote:
>
> 5.10.3 with patch compiles fine, but does not solve the issue.

Duh. adding the read_iter only fixes kernel_read(). For splice, it also needs a

        .splice_read = generic_file_splice_read,

in the file operations, something like this...

Does that get things working?

              Linus

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 fs/proc_namespace.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index e59d4bb3a89e..eafb75755fa3 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -320,7 +320,8 @@ static int mountstats_open(struct inode *inode, struct file *file)
 
 const struct file_operations proc_mounts_operations = {
 	.open		= mounts_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -328,7 +329,8 @@ const struct file_operations proc_mounts_operations = {
 
 const struct file_operations proc_mountinfo_operations = {
 	.open		= mountinfo_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -336,7 +338,8 @@ const struct file_operations proc_mountinfo_operations = {
 
 const struct file_operations proc_mountstats_operations = {
 	.open		= mountstats_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 };