On Thu, May 27, 2021 at 08:47:18AM +1000, Dave Chinner wrote:
> From : Christoph Hellwig <hch@xxxxxx>
>
> ->b_offset can only be non-zero for _XBF_KMEM backed buffers, so
> remove all code dealing with it for page backed buffers.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> [dgc: modified to fit this patchset]
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
I think it's the case that the only time we'd end up with a nonzero
b_offset is if the kmem_alloc returns a slab object in the middle of a
page, right? i.e. vmalloc is supposed to give us full pages, and we
hope that nobody ever sells a device with a 64k dma alignment...?
Assuming that's right,
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_buf.c | 8 +++-----
> fs/xfs/xfs_buf.h | 3 ++-
> 2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index d15999c41885..87151d78a0d8 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -79,7 +79,7 @@ static inline int
> xfs_buf_vmap_len(
> struct xfs_buf *bp)
> {
> - return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
> + return (bp->b_page_count * PAGE_SIZE);
> }
>
> /*
> @@ -281,7 +281,7 @@ xfs_buf_free_pages(
> ASSERT(bp->b_flags & _XBF_PAGES);
>
> if (xfs_buf_is_vmapped(bp))
> - vm_unmap_ram(bp->b_addr - bp->b_offset, bp->b_page_count);
> + vm_unmap_ram(bp->b_addr, bp->b_page_count);
>
> for (i = 0; i < bp->b_page_count; i++) {
> if (bp->b_pages[i])
> @@ -442,7 +442,7 @@ _xfs_buf_map_pages(
> ASSERT(bp->b_flags & _XBF_PAGES);
> if (bp->b_page_count == 1) {
> /* A single page buffer is always mappable */
> - bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
> + bp->b_addr = page_address(bp->b_pages[0]);
> } else if (flags & XBF_UNMAPPED) {
> bp->b_addr = NULL;
> } else {
> @@ -469,7 +469,6 @@ _xfs_buf_map_pages(
>
> if (!bp->b_addr)
> return -ENOMEM;
> - bp->b_addr += bp->b_offset;
> }
>
> return 0;
> @@ -1680,7 +1679,6 @@ xfs_buf_offset(
> if (bp->b_addr)
> return bp->b_addr + offset;
>
> - offset += bp->b_offset;
> page = bp->b_pages[offset >> PAGE_SHIFT];
> return page_address(page) + (offset & (PAGE_SIZE-1));
> }
> diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
> index 459ca34f26f5..464dc548fa23 100644
> --- a/fs/xfs/xfs_buf.h
> +++ b/fs/xfs/xfs_buf.h
> @@ -167,7 +167,8 @@ struct xfs_buf {
> atomic_t b_pin_count; /* pin count */
> atomic_t b_io_remaining; /* #outstanding I/O requests */
> unsigned int b_page_count; /* size of page array */
> - unsigned int b_offset; /* page offset in first page */
> + unsigned int b_offset; /* page offset of b_addr,
> + only for _XBF_KMEM buffers */
> int b_error; /* error code on I/O */
>
> /*
> --
> 2.31.1
>
