On 28/02/2025 01:19, Darrick J. Wong wrote:
+ if (ret == -EAGAIN && !(iocb->ki_flags & IOCB_NOWAIT) && + !(dio_flags & IOMAP_DIO_ATOMIC_SW)) { + xfs_iunlock(ip, iolock); + dio_flags = IOMAP_DIO_ATOMIC_SW | IOMAP_DIO_FORCE_WAIT;One last little nit here: if the filesystem doesn't have reflink, you can't use copy on write as a fallback. /* * The atomic write fallback uses out of place writes * implemented with the COW code, so we must fail the * atomic write if that is not supported. */ if (!xfs_has_reflink(ip->i_mount)) return -EOPNOTSUPP; dio_flags = IOMAP_DIO_ATOMIC_SW | IOMAP_DIO_FORCE_WAIT;
Currently the awu max is limited to 1x FS block if no reflink, and then we check the write length against awu max in xfs_file_write_iter() for IOCB_ATOMIC. And the xfs iomap would not request a SW-based atomic write for 1x FS block. So in a around-about way we are checking it.
So let me know if you would still like that additional check - it seems sensible to add it.
Cheers, John
