Commit-ID: abd08d7d245397bcbded8c6c29ff79a36b3875b0 Gitweb: https://git.kernel.org/tip/abd08d7d245397bcbded8c6c29ff79a36b3875b0 Author: Dan Williams <[email protected]> AuthorDate: Sun, 8 Jul 2018 13:46:07 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 16 Jul 2018 00:05:05 +0200
lib/iov_iter: Document _copy_to_iter_flushcache() Add some theory of operation documentation to _copy_to_iter_flushcache(). Reported-by: Al Viro <[email protected]> Signed-off-by: Dan Williams <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Tony Luck <[email protected]> Link: http://lkml.kernel.org/r/153108276767.37979.9462477994086841699.st...@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar <[email protected]> --- lib/iov_iter.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 94fa361be7bb..09fb73ad9d54 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -727,6 +727,20 @@ size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i) EXPORT_SYMBOL(_copy_from_iter_nocache); #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE +/** + * _copy_from_iter_flushcache - write destination through cpu cache + * @addr: destination kernel address + * @bytes: total transfer length + * @iter: source iterator + * + * The pmem driver arranges for filesystem-dax to use this facility via + * dax_copy_from_iter() for ensuring that writes to persistent memory + * are flushed through the CPU cache. It is differentiated from + * _copy_from_iter_nocache() in that guarantees all data is flushed for + * all iterator types. The _copy_from_iter_nocache() only attempts to + * bypass the cache for the ITER_IOVEC case, and on some archs may use + * instructions that strand dirty-data in the cache. + */ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i) { char *to = addr;
