From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Liu Hui" Subject: [PATCH]Fix for map_private_extent_buffer to handle extent which is not page alignment Date: Thu, 4 Dec 2008 22:08:36 +0800 Message-ID: <2c3b11250812040608r6eb4eb59xcdb6f53a72b5feb6@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: linux-btrfs@vger.kernel.org Return-path: List-ID: Hi, Now, BTRFS only supports page alignment extent. But in map_private_extent(), there are already some codes to handle the extent which is not page alignment. For example, map_private_extent_buffer also wants to handle a extent which is 7K length properly. The problem is the codes are not enough, e.g. in the following figure, map_private_extent_buffer can handle extent1, but it can't take the right behavior to handle extent2. This patch fixs it. PS:Please use the mono font to view the ASCII figures, thanks. |-extent1-| +-----++-----+ |page1||page2| +-----++-----+ |-extent2-| +-----++-----+ |page1||page2| +-----++-----+ -- Thanks & Best Regards Liu Hui -- diff --git a/extent_io.c b/extent_io.c index c3dfe2a..cac47d1 100644 --- a/extent_io.c +++ b/extent_io.c @@ -3426,9 +3426,11 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start, char *kaddr; struct page *p; size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1); + size_t last_offset; unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT; unsigned long end_i = (start_offset + start + min_len - 1) >> PAGE_CACHE_SHIFT; + unsigned long last_i = (start_offset + eb->len - 1) >> PAGE_CACHE_SHIFT; if (i != end_i) return -EINVAL; @@ -3440,8 +3442,16 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start, offset = 0; *map_start = ((u64)i << PAGE_CACHE_SHIFT) - start_offset; } + + if (i == last_i) + last_offset = ((u64)(i + 1) << PAGE_CACHE_SHIFT) - start_offset + - eb->len; + else + last_offset = 0; + if (start + min_len > eb->len) { -printk("bad mapping eb start %Lu len %lu, wanted %lu %lu\n", eb->start, eb->len, start, min_len); + printk("bad mapping eb start %Lu len %lu, wanted %lu %lu\n", + eb->start, eb->len, start, min_len); WARN_ON(1); } @@ -3449,7 +3459,7 @@ printk("bad mapping eb start %Lu len %lu, wanted %lu %lu\n", eb->start, eb->len, kaddr = kmap_atomic(p, km); *token = kaddr; *map = kaddr + offset; - *map_len = PAGE_CACHE_SIZE - offset; + *map_len = PAGE_CACHE_SIZE - offset - last_offset; return 0; } EXPORT_SYMBOL(map_private_extent_buffer);