The patch titled
Subject: mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers
has been added to the -mm tree. Its filename is
mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch
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------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers
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>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/staging/lustre/lustre/llite/llite_mmap.c | 4 +---
include/linux/buffer_head.h | 4 +---
2 files changed, 2 insertions(+), 6 deletions(-)
diff -puN drivers/staging/lustre/lustre/llite/llite_mmap.c~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers drivers/staging/lustre/lustre/llite/llite_mmap.c
--- a/drivers/staging/lustre/lustre/llite/llite_mmap.c~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers
+++ a/drivers/staging/lustre/lustre/llite/llite_mmap.c
@@ -390,15 +390,13 @@ 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;
diff -puN include/linux/buffer_head.h~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers include/linux/buffer_head.h
--- a/include/linux/buffer_head.h~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers
+++ a/include/linux/buffer_head.h
@@ -243,12 +243,10 @@ 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 -mm which might be from jack@xxxxxxx are
mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers.patch
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