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ubifs: add missing ui pointer in debugging code

Message ID 1401193701.1304.135.camel@sauron.fi.intel.com
State Accepted
Headers show

Commit Message

Artem Bityutskiy May 27, 2014, 12:28 p.m. UTC 
On Wed, 2014-05-14 at 15:32 +0800, hujianyang wrote:
> On 2014/5/14 4:27, Daniel Golle wrote:
> > If UBIFS_DEBUG is defined an additional assertion of the ui_lock
> > spinlock in do_writepage cannot compile because the ui pointer has not
> > been previously declared.
> > 
> > Fix this by declaring and initializing the ui pointer in case
> > UBIFS_DEBUG is defined.
> > 
> > Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> > ---
> >  fs/ubifs/file.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> > index 4f34dba..e13ec5e 100644
> > --- a/fs/ubifs/file.c
> > +++ b/fs/ubifs/file.c
> > @@ -903,6 +903,7 @@ static int do_writepage(struct page *page, int len)
> >  	struct ubifs_info *c = inode->i_sb->s_fs_info;
> >  
> >  #ifdef UBIFS_DEBUG
> > +	struct ubifs_inode *ui = ubifs_inode(inode);
> >  	spin_lock(&ui->ui_lock);
> >  	ubifs_assert(page->index <= ui->synced_i_size << PAGE_CACHE_SIZE);
> 
> I think here should be:
>   	ubifs_assert(page->index <= ui->synced_i_size >> PAGE_CACHE_SHIFT);

I think you are right, thanks. I've just applied this patch:

Author: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date:   Tue May 27 15:24:39 2014 +0300

    UBIFS: fix debugging check
    
    The debugging check which verifies that we never write outside of the file
    length was incorrect, since it was multiplying file length by the page size,
    instead of dividing. Fix this.
    
    Spotted-by: hujianyang <hujianyang@huawei.com>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Comments

hujianyang May 28, 2014, 2:27 a.m. UTC | #1 
Hi Artem,

I think you made a small mistake:

>         spin_lock(&ui->ui_lock);
> -       ubifs_assert(page->index <= ui->synced_i_size << PAGE_CACHE_SIZE);
> +       ubifs_assert(page->index <= ui->synced_i_size >> PAGE_CACHE_SIZE);

Here should be PAGE_CACHE_SHIFT, not PAGE_CACHE_SIZE.

Thanks.

Hu
Artem Bityutskiy May 28, 2014, 8:04 a.m. UTC | #2 
On Wed, 2014-05-28 at 10:27 +0800, hujianyang wrote:
> Hi Artem,
> 
> I think you made a small mistake:

Indeed, and not that small, even. I'll fix this, thanks!

If I was writing this code now, I would not bother using shifts, I'd
just use divisions, which are simpler and less error-prone. And modern
compilers are smart enough to optimize the code to use shifts when the
divider is a constant.
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Patch

diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 727506b..2767ffb 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -905,7 +905,7 @@  static int do_writepage(struct page *page, int len)
 #ifdef UBIFS_DEBUG
        struct ubifs_inode *ui = ubifs_inode(inode);
        spin_lock(&ui->ui_lock);
-       ubifs_assert(page->index <= ui->synced_i_size << PAGE_CACHE_SIZE);
+       ubifs_assert(page->index <= ui->synced_i_size >> PAGE_CACHE_SIZE);
        spin_unlock(&ui->ui_lock);
 #endif