Nick Piggin <npiggin@xxxxxxx> writes:
> 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?
Yes, this patch doesn't pass zero-length to prepare_write. However,
I'm not checking this patch is ok for reiserfs...
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
-
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