On Tue, Nov 07, 2023 at 07:41:49PM +0000, Matthew Wilcox (Oracle) wrote:
> The calculation of block from index doesn't work for devices with a block
> size larger than PAGE_SIZE as we end up shifting by a negative number.
> Instead, calculate the number of the first block from the folio's
> position in the block device. We no longer need to pass sizebits to
> grow_dev_folio().
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Not totally related to the patch but even though the variable "block"
is sector_t type, but it represents the block number in logical block
size unit of the device? My mind directly went to sector_t being 512
bytes blocks.
But the math checks out.
Reviewed-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
> ---
> fs/buffer.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 8dad6c691e14..cd114110b27f 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -995,11 +995,12 @@ static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
> * Initialise the state of a blockdev folio's buffers.
> */
> static sector_t folio_init_buffers(struct folio *folio,
> - struct block_device *bdev, sector_t block, int size)
> + struct block_device *bdev, int size)
> {
> struct buffer_head *head = folio_buffers(folio);
> struct buffer_head *bh = head;
> bool uptodate = folio_test_uptodate(folio);
> + sector_t block = folio_pos(folio) / size;
> sector_t end_block = blkdev_max_block(bdev, size);
>
> do {
> @@ -1032,7 +1033,7 @@ static sector_t folio_init_buffers(struct folio *folio,
> * we succeeded, or the caller should retry.
> */
> static bool grow_dev_folio(struct block_device *bdev, sector_t block,
> - pgoff_t index, unsigned size, int sizebits, gfp_t gfp)
> + pgoff_t index, unsigned size, gfp_t gfp)
> {
> struct inode *inode = bdev->bd_inode;
> struct folio *folio;
> @@ -1047,8 +1048,7 @@ static bool grow_dev_folio(struct block_device *bdev, sector_t block,
> bh = folio_buffers(folio);
> if (bh) {
> if (bh->b_size == size) {
> - end_block = folio_init_buffers(folio, bdev,
> - (sector_t)index << sizebits, size);
> + end_block = folio_init_buffers(folio, bdev, size);
> goto unlock;
> }
>
> @@ -1069,8 +1069,7 @@ static bool grow_dev_folio(struct block_device *bdev, sector_t block,
> */
> spin_lock(&inode->i_mapping->private_lock);
> link_dev_buffers(folio, bh);
> - end_block = folio_init_buffers(folio, bdev,
> - (sector_t)index << sizebits, size);
> + end_block = folio_init_buffers(folio, bdev, size);
> spin_unlock(&inode->i_mapping->private_lock);
> unlock:
> folio_unlock(folio);
> @@ -1105,7 +1104,7 @@ static bool grow_buffers(struct block_device *bdev, sector_t block,
> }
>
> /* Create a folio with the proper size buffers */
> - return grow_dev_folio(bdev, block, index, size, sizebits, gfp);
> + return grow_dev_folio(bdev, block, index, size, gfp);
> }
>
> static struct buffer_head *
> --
> 2.42.0
>
--
Pankaj Raghav
