Messages in this thread | | | Date | Tue, 22 Jun 2004 12:05:40 -0700 | From | Andrew Morton <> | Subject | Re: deadlocks caused by ext3/reiser dirty_inode calls during do_mmap_pgoff |
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Chris Mason <mason@suse.com> wrote: > > On Mon, 2004-06-21 at 20:13, Andrew Morton wrote: > > > It's super-improbable because we fault the source page in by hand in > > generic_file_aio_write_nolock() via fault_in_pages_readable(). Of course, > > that prefaulting isn't 100% reliable either, because the VM can come in and > > steal the page (or at least unmap its pte) before we get to doing the copy. > > > > I think we can fix both problems by changing filemap_copy_from_user() and > > filemap_copy_from_user_iovec() to not fall back to kmap() - just fail the > > copy in some way if the atomic copy failed. Then, in > > generic_file_aio_write_nolock(), do a zero-length ->commit_write(), > > put_page(), then go back and retry the whole thing, starting with > > fault_in_pages_readable(). > > Oh, just realized this will break our data=ordered setup. prepare_write > is going to do things like allocating blocks in the file etc etc. If we > close the transaction via commit_write(0 size) and crash, we'll leak.
OK, then just zero the pagecache page between `from' and `to' and call ->commit_write() with unmodified `from' and `to'?
> We might need to do prefault + pin on the user pages.
That's always been the correct way to fix these problems, but it involves a pagetable walk, which requires page_table_lock. Not a popular thing to be doing on the write() fastpath. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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