Re: [PATCH v2] hfsplus: avoid crash on failed block map free

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 13 Nov 2012 13:31:05 +0400
Vyacheslav Dubeyko <slava@dubeyko.com> wrote:

> If the read fails we kmap an error code. This doesn't end well. Instead print a critical error and pray. This mirrors the rest of the fs behaviour with critical error cases.
> 
> ...
>
> index 4cfbe2e..6feefc0 100644
> --- a/fs/hfsplus/bitmap.c
> +++ b/fs/hfsplus/bitmap.c
> @@ -176,12 +176,14 @@ int hfsplus_block_free(struct super_block *sb, u32 offset, u32 count)
>  	dprint(DBG_BITMAP, "block_free: %u,%u\n", offset, count);
>  	/* are all of the bits in range? */
>  	if ((offset + count) > sbi->total_blocks)
> -		return -2;
> +		return -ENOENT;
>  
>  	mutex_lock(&sbi->alloc_mutex);
>  	mapping = sbi->alloc_file->i_mapping;
>  	pnr = offset / PAGE_CACHE_BITS;
>  	page = read_mapping_page(mapping, pnr, NULL);
> +	if (IS_ERR(page))
> +		goto kaboom;
>  	pptr = kmap(page);
>  	curr = pptr + (offset & (PAGE_CACHE_BITS - 1)) / 32;
>  	end = pptr + PAGE_CACHE_BITS / 32;
> @@ -214,6 +216,8 @@ int hfsplus_block_free(struct super_block *sb, u32 offset, u32 count)
>  		set_page_dirty(page);
>  		kunmap(page);
>  		page = read_mapping_page(mapping, ++pnr, NULL);
> +		if (IS_ERR(page))
> +			goto kaboom;
>  		pptr = kmap(page);
>  		curr = pptr;
>  		end = pptr + PAGE_CACHE_BITS / 32;
> @@ -232,4 +236,11 @@ out:
>  	mutex_unlock(&sbi->alloc_mutex);
>  
>  	return 0;
> +
> +kaboom:
> +	printk(KERN_CRIT "hfsplus: unable to mark blocks free: error %ld\n",
> +			PTR_ERR(page));
> +	mutex_unlock(&sbi->alloc_mutex);
> +
> +	return -EIO;
>  }

It looks better than what we currently have!

The code is missing a flush_dcache_page()?  We should have one in there
after the CPU has modified userspace-mappable page contents.


btw, I still have question marks over your earlier patches:

hfsplus-add-on-disk-layout-declarations-related-to-attributes-tree.patch
hfsplus-add-functionality-of-manipulating-by-records-in-attributes-tree.patch
hfsplus-rework-functionality-of-getting-setting-and-deleting-of-extended-attributes.patch
hfsplus-add-support-of-manipulation-by-attributes-file.patch
hfsplus-add-support-of-manipulation-by-attributes-file-checkpatch-fixes.patch
hfsplus-code-style-fixes-reworked-support-of-extended-attributes.patch

Christoph sounded unhappy, but the review discussion petered out?