Re: [PATCH 04/18] fs/buffer.c: use accessor function to translate page index to sectors

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On 10/20/23 21:37, Matthew Wilcox wrote:
On Mon, Sep 18, 2023 at 01:04:56PM +0200, Hannes Reinecke wrote:
Use accessor functions block_index_to_sector() and block_sector_to_index()
to translate the page index into the block sector and vice versa.

You missed two in grow_dev_page() (which I just happened upon):

         bh = folio_buffers(folio);
         if (bh) {
                 if (bh->b_size == size) {
                         end_block = folio_init_buffers(folio, bdev,
                                         (sector_t)index << sizebits, size);
                         goto done;
                 }
...
         spin_lock(&inode->i_mapping->private_lock);
         link_dev_buffers(folio, bh);
         end_block = folio_init_buffers(folio, bdev,
                         (sector_t)index << sizebits, size);

Can UBSAN be of help here?  It should catch shifting by a negative
amount.  That sizebits is calculated in grow_buffers:

         sizebits = PAGE_SHIFT - __ffs(size);

Ah, thanks. I'm currently working with Luis and Pankay to get a combined patchset; I'll make sure to have that included.

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman





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