On Fri, Dec 01, 2006 at 07:14:28AM +0900, OGAWA Hirofumi wrote:
>
> quick look. Doesn't this break reiserfs? IIRC, the reiserfs is using
> it for another reason. I was also working for this, but I lost the
> thread of this, sorry.
>
> I found some another users (affs, hfs, hfsplus). Those seem have same
> problem, but probably those also can use this...
>
> What do you think?
> --
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
>
>
>
> Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
> ---
>
> fs/buffer.c | 59 +++++++++++++++++---------------------------
> fs/fat/file.c | 2 -
> include/linux/buffer_head.h | 1
> 3 files changed, 24 insertions(+), 38 deletions(-)
>
> diff -puN fs/buffer.c~generic_cont_expand-avoid-zero-size fs/buffer.c
> --- linux-2.6/fs/buffer.c~generic_cont_expand-avoid-zero-size 2006-11-13 01:42:01.000000000 +0900
> +++ linux-2.6-hirofumi/fs/buffer.c 2006-11-13 02:16:20.000000000 +0900
> @@ -2004,18 +2004,24 @@ int block_read_full_page(struct page *pa
> return 0;
> }
>
> -/* utility function for filesystems that need to do work on expanding
> +/*
> + * utility function for filesystems that need to do work on expanding
> * truncates. Uses prepare/commit_write to allow the filesystem to
> * deal with the hole.
> */
> -static int __generic_cont_expand(struct inode *inode, loff_t size,
> - pgoff_t index, unsigned int offset)
> +int generic_cont_expand(struct inode *inode, loff_t size)
> {
> struct address_space *mapping = inode->i_mapping;
> + loff_t pos = inode->i_size;
> struct page *page;
> unsigned long limit;
> + pgoff_t index;
> + unsigned int from, to;
> + void *kaddr;
> int err;
>
> + WARN_ON(pos >= size);
> +
> err = -EFBIG;
> limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
> if (limit != RLIM_INFINITY && size > (loff_t)limit) {
> @@ -2025,11 +2031,18 @@ static int __generic_cont_expand(struct
> if (size > inode->i_sb->s_maxbytes)
> goto out;
>
> + index = (size - 1) >> PAGE_CACHE_SHIFT;
> + to = size - ((loff_t)index << PAGE_CACHE_SHIFT);
> + if (index != (pos >> PAGE_CACHE_SHIFT))
> + from = 0;
> + else
> + from = pos & (PAGE_CACHE_SIZE - 1);
> +
> err = -ENOMEM;
> page = grab_cache_page(mapping, index);
> if (!page)
> goto out;
> - err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
> + err = mapping->a_ops->prepare_write(NULL, page, from, to);
> if (err) {
> /*
> * ->prepare_write() may have instantiated a few blocks
> @@ -2041,7 +2054,12 @@ static int __generic_cont_expand(struct
> goto out;
> }
>
> - err = mapping->a_ops->commit_write(NULL, page, offset, offset);
> + kaddr = kmap_atomic(page, KM_USER0);
> + memset(kaddr + from, 0, to - from);
> + flush_dcache_page(page);
> + kunmap_atomic(kaddr, KM_USER0);
> +
> + err = mapping->a_ops->commit_write(NULL, page, from, to);
So basically this is changing from having prepare_write do all the
zeroing, to zeroing the last page in generic_cont_expand, so that
we don't have to pass a zero-length to prepare_write?
-
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