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mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers

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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@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jan Kara 2017-02-08 14:30:53 -08:00 committed by Linus Torvalds
parent ed5bd7dc88
commit 0911d0041c
2 changed files with 2 additions and 6 deletions
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4
drivers/staging/lustre/lustre/llite/llite_mmap.c
View file

@ -390,15 +390,13 @@ static int ll_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
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;

4
include/linux/buffer_head.h
View file

@ -243,12 +243,10 @@ static inline int block_page_mkwrite_return(int err)
{
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;
}