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SubjectRe: [PATCH] Propagate CRAMFS uncompression errors
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On Mon, 2009-02-09 at 19:48 -0800, Andrew Morton wrote:
...
>
> umm...
>
> Nope, it's still not right. We'll treat this case:
>
> if (compr_len == 0)
> ; /* hole */
>
> as an IO error. grr.
>
> --- a/fs/cramfs/inode.c~cramfs-propagate-uncompression-errors
> +++ a/fs/cramfs/inode.c
> @@ -477,7 +477,7 @@ static int cramfs_readpage(struct file *
> mutex_unlock(&read_mutex);
> pgdata = kmap(page);
> if (compr_len == 0)
> - ; /* hole */
> + goto out; /* hole */
> else if (compr_len > (PAGE_CACHE_SIZE << 1))
> printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
> else {
> @@ -488,12 +488,20 @@ static int cramfs_readpage(struct file *
> compr_len);
> mutex_unlock(&read_mutex);
> }
> - } else
> - pgdata = kmap(page);
> - memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
> - kunmap(page);
> - flush_dcache_page(page);
> - SetPageUptodate(page);
> +
> + if (bytes_filled == 0) {
> + /* Decompression error */
> + ClearPageUptodate(page);
> + SetPageError(page);
> + } else {
> + memset(pgdata + bytes_filled, 0,
> + PAGE_CACHE_SIZE - bytes_filled);
> + flush_dcache_page(page);
> + SetPageUptodate(page);
> + }
> + kunmap(page);
> + }
> +out:
> unlock_page(page);
> return 0;
> }

Is that actually an error. The comment in the code is, uh, a bit terse,
but I took it to mean that there was a deliberate hole, just like holes
in files that should read as all zeroes. But even if it's actually an
error, we still need to kunmap the page
--
David VomLehn, dvomlehn@cisco.com




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