Hi there's some work to make users of fscache on-demand mode support PAGE_SIZE larger than 4KB (e.g. 16/64KB in aarch64) [1]. I think they may be also useful for other users of fscache/cachefiles. Strictly speacking, patch 1 is a bug fix though the issue doesn't cause serious harm when erofs doesn't support large PAGE_SIZE (other than 4KB). __cachefiles_prepare_write() will align the requested file range to PAGE_SIZE boundary. This is reasonable for libnetfs as libnetfs will construct an iter with the aligned file range from the ground. While for fscache on-demand mode, cachefiles_ondemand_fd_write_iter() is called by the user daemon, and thus it is unexpected to align the file range to PAGE_SIZE boundary, as the iov_iter/kiocb is given by the user daemon. If the given file range is not aligned with the block size of the backing filesystem, let's fail the write directly. Patch 2 adds a new helper, by which users of fscache on-demand mode could wait for the wrangling of the cache object and then derive the object size (set in cachefiles_ondemand_copen()). fscache_begin_read_operation() is not feasible for this purpose as in this case @want_state is FSCACHE_WANT_PARAMS and it will not wait there for object wrangling when cookie is in FSCACHE_COOKIE_STATE_CREATING state. An example use case of this helper is illustrated in [2]. Any comment is welcomed. [1] https://lore.kernel.org/all/20230221091719.126127-1-jefflexu@xxxxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/all/20230221091719.126127-2-jefflexu@xxxxxxxxxxxxxxxxx/ Jingbo Xu (2): cachefiles: don't align the write IO in ondemand mode fscache: introduce fscache_begin_wait_operation() helper fs/cachefiles/ondemand.c | 3 ++- fs/fscache/io.c | 9 +++++++++ include/linux/fscache.h | 22 ++++++++++++++++++++++ 3 files changed, 33 insertions(+), 1 deletion(-) -- 2.19.1.6.gb485710b -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/linux-cachefs
