Re: [RFC][PATCH] EXT3: problem with page fault inside a transaction

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Dmitriy Monakhov wrote:
Andrew Morton <[email protected]> writes:

With the stuff Nick and I are looking at, we won't take pagefaults inside
prepare_write()/commit_write() any more.

I'sorry may be i've missed something, but how cant you prevent this?

Let's look at generic_file_buffered_write:
#### force page fault
fault_in_pages_readable();

### find and lock page
 __grab_cache_page()

#### allocate blocks.This may result in low memory condition
#### try_to_free_pages->shrink_caches() and etc. a_ops->prepare_write()

### can anyone guarantee that page fault hasn't  happened by now ?

Yes. Do an atomic copy, which will early exit from the pagefault handler
and return a short copy. Then close up the write, drop the page lock,
and rerun the fault_in_pages_readable, which will do the full pagefaults
for us, then try again.

Regardless of what you do to ext3, the VM just can't handle a fault
here anyway.

--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com -
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux