On Mon, Jan 06, 2025 at 04:15:57PM +0100, Christoph Hellwig wrote: > For I/O to reflinked blocks we always need to write an entire new > file system block, and the code enforces the file system block alignment > for the entire file if it has any reflinked blocks. > > Use the new STATX_DIO_READ_ALIGN flag to report the asymmetric read > vs write alignments for reflinked files. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > --- > fs/xfs/xfs_iops.c | 24 +++++++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c > index 6b0228a21617..053d05f5567d 100644 > --- a/fs/xfs/xfs_iops.c > +++ b/fs/xfs/xfs_iops.c > @@ -580,9 +580,27 @@ xfs_report_dioalign( > struct xfs_buftarg *target = xfs_inode_buftarg(ip); > struct block_device *bdev = target->bt_bdev; > > - stat->result_mask |= STATX_DIOALIGN; > + stat->result_mask |= STATX_DIOALIGN | STATX_DIO_READ_ALIGN; > stat->dio_mem_align = bdev_dma_alignment(bdev) + 1; > - stat->dio_offset_align = bdev_logical_block_size(bdev); > + stat->dio_read_offset_align = bdev_logical_block_size(bdev); > + > + /* > + * On COW inodes we are forced to always rewrite an entire file system > + * block or RT extent. > + * > + * Because applications assume they can do sector sized direct writes > + * on XFS we fall back to buffered I/O for sub-block direct I/O in that > + * case. Because that needs to copy the entire block into the buffer > + * cache it is highly inefficient and can easily lead to page cache > + * invalidation races. > + * > + * Tell applications to avoid this case by reporting the natively > + * supported direct I/O read alignment. > + */ > + if (xfs_is_cow_inode(ip)) > + stat->dio_offset_align = xfs_inode_alloc_unitsize(ip); > + else > + stat->dio_offset_align = stat->dio_read_offset_align; This is a good improvement! Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx> --D > } > > static void > @@ -658,7 +676,7 @@ xfs_vn_getattr( > stat->rdev = inode->i_rdev; > break; > case S_IFREG: > - if (request_mask & STATX_DIOALIGN) > + if (request_mask & (STATX_DIOALIGN | STATX_DIO_READ_ALIGN)) > xfs_report_dioalign(ip, stat); > if (request_mask & STATX_WRITE_ATOMIC) > xfs_report_atomic_write(ip, stat); > -- > 2.45.2 > >
