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SubjectRe: [PATCH v7 11/22] Replace ext2_clear_xip_target with dax_clear_blocks
On Sun 23-03-14 15:08:37, Matthew Wilcox wrote:
> This is practically generic code; other filesystems will want to call
> it from other places, but there's nothing ext2-specific about it.
>
> Make it a little more generic by allowing it to take a count of the number
> of bytes to zero rather than fixing it to a single page. Thanks to Dave
> Hansen for suggesting that I need to call cond_resched() if zeroing more
> than one page.
Another day, some more review ;) Comments below.
>
> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
> ---
> fs/dax.c | 34 ++++++++++++++++++++++++++++++++++
> fs/ext2/inode.c | 8 +++++---
> fs/ext2/xip.c | 23 -----------------------
> fs/ext2/xip.h | 3 ---
> include/linux/fs.h | 6 ++++++
> 5 files changed, 45 insertions(+), 29 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 7271be0..45a0a41 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -23,9 +23,43 @@
> #include <linux/memcontrol.h>
> #include <linux/mm.h>
> #include <linux/mutex.h>
> +#include <linux/sched.h>
> #include <linux/uio.h>
> #include <linux/vmstat.h>
>
> +int dax_clear_blocks(struct inode *inode, sector_t block, long size)
> +{
> + struct block_device *bdev = inode->i_sb->s_bdev;
> + const struct block_device_operations *ops = bdev->bd_disk->fops;
> + sector_t sector = block << (inode->i_blkbits - 9);
> + unsigned long pfn;
> +
> + might_sleep();
> + do {
> + void *addr;
> + long count = ops->direct_access(bdev, sector, &addr, &pfn,
> + size);
So do you assume blocksize == PAGE_SIZE here? If not, addr could be in
the middle of the page AFAICT.

> + if (count < 0)
> + return count;
> + while (count >= PAGE_SIZE) {
> + clear_page(addr);
> + addr += PAGE_SIZE;
> + size -= PAGE_SIZE;
> + count -= PAGE_SIZE;
> + sector += PAGE_SIZE / 512;
> + cond_resched();
> + }
> + if (count > 0) {
> + memset(addr, 0, count);
> + sector += count / 512;
> + size -= count;
> + }
> + } while (size);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(dax_clear_blocks);
> +
> static long dax_get_addr(struct inode *inode, struct buffer_head *bh,
> void **addr)
> {
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index b156fe8..a9346a9 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -733,10 +733,12 @@ static int ext2_get_blocks(struct inode *inode,
>
> if (IS_DAX(inode)) {
> /*
> - * we need to clear the block
> + * block must be initialised before we put it in the tree
> + * so that it's not found by another thread before it's
> + * initialised
> */
> - err = ext2_clear_xip_target (inode,
> - le32_to_cpu(chain[depth-1].key));
> + err = dax_clear_blocks(inode, le32_to_cpu(chain[depth-1].key),
> + count << inode->i_blkbits);
Umm 'count' looks wrong here. You want to clear only one block, don't
you?

> if (err) {
> mutex_unlock(&ei->truncate_mutex);
> goto cleanup;
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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