Ceph In Linux 7.4 Adds Global Mount Option For Lazy I/O

The Ceph kernel client changes have been submitted for Linux 7.4 ahead of its merge window expected to wrap up on Sunday. Ceph has supported an ioctl for enabling lazy I/O on a per-file basis while the new code for Linux 7.4 is adding the "lazyio" mount option if wanting to enable lazy I/O globally. Ceph's lazy I/O mode will enable it for all regular files at open time. The mode allows for buffered I/O via the page cache, even if multiple clients have the file open for write. That scenario is intended for HPC workloads and similar that can cope with relaxed cache coherency. In addition to the "lazyio" mount option for Ceph, the inine data feature that has been around for more than a decade as an experimental feature and deprecated since 2020 is in the process of being removed. For Linux 7.4 the kernel adds a CEPH_FS_INLINE_DATA Kconfig option that defaults to off. So those still relying on Ceph inline data support will now need to ensure that CEPH_FS_INLINE_DATA=Y is set to continue using it. But in a future release that plan to remove the deprecated code outright. Ceoh inline data support was added in Linux 3.19 back in 2014 for allowing small files to be stored directly inside the file's inode or metadata data structures rather than separate RADOS objects. The Ceph pull request also brings a number of bug fixes and other code clean-ups for Linux 7.4.