This is a note to let you know that I've just added the patch titled
mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Dec 6 16:43:17 CET 2017
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 8 Feb 2017 14:30:53 -0800
Subject: mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers
From: Jan Kara <jack@xxxxxxx>
[ Upstream commit 0911d0041c22922228ca52a977d7b0b0159fee4b ]
Some ->page_mkwrite handlers may return VM_FAULT_RETRY as its return
code (GFS2 or Lustre can definitely do this). However VM_FAULT_RETRY
from ->page_mkwrite is completely unhandled by the mm code and results
in locking and writeably mapping the page which definitely is not what
the caller wanted.
Fix Lustre and block_page_mkwrite_ret() used by other filesystems
(notably GFS2) to return VM_FAULT_NOPAGE instead which results in
bailing out from the fault code, the CPU then retries the access, and we
fault again effectively doing what the handler wanted.
Link: http://lkml.kernel.org/r/20170203150729.15863-1-jack@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Jinshan Xiong <jinshan.xiong@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/lustre/lustre/llite/llite_mmap.c | 4 +---
include/linux/buffer_head.h | 4 +---
2 files changed, 2 insertions(+), 6 deletions(-)
--- a/drivers/staging/lustre/lustre/llite/llite_mmap.c
+++ b/drivers/staging/lustre/lustre/llite/llite_mmap.c
@@ -402,15 +402,13 @@ static int ll_page_mkwrite(struct vm_are
result = VM_FAULT_LOCKED;
break;
case -ENODATA:
+ case -EAGAIN:
case -EFAULT:
result = VM_FAULT_NOPAGE;
break;
case -ENOMEM:
result = VM_FAULT_OOM;
break;
- case -EAGAIN:
- result = VM_FAULT_RETRY;
- break;
default:
result = VM_FAULT_SIGBUS;
break;
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -234,12 +234,10 @@ static inline int block_page_mkwrite_ret
{
if (err == 0)
return VM_FAULT_LOCKED;
- if (err == -EFAULT)
+ if (err == -EFAULT || err == -EAGAIN)
return VM_FAULT_NOPAGE;
if (err == -ENOMEM)
return VM_FAULT_OOM;
- if (err == -EAGAIN)
- return VM_FAULT_RETRY;
/* -ENOSPC, -EDQUOT, -EIO ... */
return VM_FAULT_SIGBUS;
}
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-4.4/mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch