On Wed 18-06-25 11:17:10, Pankaj Raghav wrote: > The maximum IO size that a block device can read as a single block is > based on the min folio order and not the PAGE_SIZE as we have bs > ps > support for block devices[1]. > > Calculate the upper limit based on the on min folio order. > > [1] https://lore.kernel.org/linux-block/20250221223823.1680616-1-mcgrof@xxxxxxxxxx/ > > Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx> ... > --- > I found this while I was adding bs > ps support to ext4. Ext4 uses this > routine to read the superblock. > > fs/buffer.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 8cf4a1dc481e..98f90da69a0a 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1121,10 +1121,11 @@ __getblk_slow(struct block_device *bdev, sector_t block, > unsigned size, gfp_t gfp) > { > bool blocking = gfpflags_allow_blocking(gfp); > + int blocklog = PAGE_SHIFT + mapping_min_folio_order(bdev->bd_mapping); > > /* Size must be multiple of hard sectorsize */ > - if (unlikely(size & (bdev_logical_block_size(bdev)-1) || > - (size < 512 || size > PAGE_SIZE))) { > + if (unlikely(size & (bdev_logical_block_size(bdev) - 1) || > + (size < 512 || size > (1U << blocklog)))) { So this doesn't quite make sense to me. Shouldn't it be capped from above by PAGE_SIZE << mapping_max_folio_order(bdev->bd_mapping)? Honza > printk(KERN_ERR "getblk(): invalid block size %d requested\n", > size); > printk(KERN_ERR "logical block size: %d\n", > > base-commit: e04c78d86a9699d136910cfc0bdcf01087e3267e > -- > 2.49.0 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
