On Tue, Jun 30, 2015 at 03:56:15PM -0400, Matthew Wilcox wrote: > > Using O_DIRECT for this seems like a pretty horrible hack, so I'd like > > to see a really good justification of using this over other interfaces. > > O_DIRECT means "bypass the page cache", which is what this does (now it's > able to apply to mmap too). It never had a meaning for mmap. > > Also it needs a Cc to linux-api and an entry in the open man page, and > > and even better explanation of why we only support this interface on > > block devices but not file systems. > > Um, we do support this for filesystems with DAX. The inconsistency we > have is that if you have a direct-access-capable block device, currently > files in a filesystem on it get the bypass-page-cache treatment, but if > you use the raw block device directly, that mapping doesn't. I don't see this O_DIRECT check done anywhere in filesystems. Filesystems seems to get your O_DIRECT treatment when mounted with the dax option as far as I can tell without the need for additional options. The block device equivalent would be a sysfs flag, which seems like the better implementation choice here. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
