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SubjectRe: [PATCH v7 18/22] xip: Add xip_zero_page_range
On Sun 23-03-14 15:08:44, Matthew Wilcox wrote:
> This new function allows us to support hole-punch for XIP files by zeroing
> a partial page, as opposed to the xip_truncate_page() function which can
> only truncate to the end of the page. Reimplement xip_truncate_page() as
> a macro that calls xip_zero_page_range().
>
> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
> [ported to 3.13-rc2]
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Two comments below...

...
> diff --git a/fs/dax.c b/fs/dax.c
> index 45a0a41..2d6b4bc 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
...
> @@ -491,11 +494,16 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
> if (buffer_written(&bh)) {
> void *addr;
> err = dax_get_addr(inode, &bh, &addr);
> - if (err)
> + if (err < 0)
> return err;
> + /*
> + * ext4 sometimes asks to zero past the end of a block. It
> + * really just wants to zero to the end of the block.
> + */
Then we should really fix ext4 I believe...

> + length = min_t(unsigned, length, PAGE_CACHE_SIZE - offset);
> memset(addr + offset, 0, length);
> }
>
> return 0;
> }
> -EXPORT_SYMBOL_GPL(dax_truncate_page);
> +EXPORT_SYMBOL_GPL(dax_zero_page_range);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index bff394d..d0381ab 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2521,6 +2521,7 @@ extern int nonseekable_open(struct inode * inode, struct file * filp);
>
> #ifdef CONFIG_FS_DAX
> int dax_clear_blocks(struct inode *, sector_t block, long size);
> +int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
> int dax_truncate_page(struct inode *, loff_t from, get_block_t);
> ssize_t dax_do_io(int rw, struct kiocb *, struct inode *, const struct iovec *,
> loff_t, unsigned segs, get_block_t, dio_iodone_t, int flags);
> @@ -2532,7 +2533,8 @@ static inline int dax_clear_blocks(struct inode *i, sector_t blk, long sz)
> return 0;
> }
>
> -static inline int dax_truncate_page(struct inode *i, loff_t frm, get_block_t gb)
> +static inline int dax_zero_page_range(struct inode *inode, loff_t from,
> + unsigned len, get_block_t gb)
> {
> return 0;
> }
> @@ -2545,6 +2547,11 @@ static inline ssize_t dax_do_io(int rw, struct kiocb *iocb, struct inode *inode,
> }
> #endif
>
> +/* Can't be a function because PAGE_CACHE_SIZE is defined in pagemap.h */
> +#define dax_truncate_page(inode, from, get_block) \
> + dax_zero_page_range(inode, from, PAGE_CACHE_SIZE, get_block)
^^^^
This should be (PAGE_CACHE_SIZE - (from & (PAGE_CACHE_SIZE - 1))), shouldn't it?

> +
> +
> #ifdef CONFIG_BLOCK
> typedef void (dio_submit_t)(int rw, struct bio *bio, struct inode *inode,

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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