On Mon, Jan 06, 2025 at 06:37:06PM +0000, John Garry wrote: >> + /* >> + * 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. > > Maybe I mis-read the complete comment, but did you really mean "natively > supported direct I/O write alignment"? You have been talking about writes > only, but then finally mention read alignment. No, this is indeed intended to talk about the different (smaller) read alignment we are now reporting. But I guess the wording is confusing enough that I should improve it?
