On Wed, May 15, 2013 at 3:16 PM, Chris Mason <chris.mason@xxxxxxxxxxxx> wrote: > Quoting Steve French (2013-05-15 16:08:16) >> On Wed, May 15, 2013 at 2:36 PM, Zach Brown <zab@xxxxxxxxxx> wrote: >> > On Wed, May 15, 2013 at 12:50:13PM -0500, Steve French wrote: >> >> Doesn't the new syscall have to invalidate the page cache pages that >> >> the server is about to overwrite as btrfs does with the following line >> >> in fs/btrfs/ioctl.c >> >> >> >> truncate_inode_pages_range(&inode->i_data, destoff, >> >> PAGE_CACHE_ALIGN(destoff + len) - 1); >> > >> > The file_operations ->copy_range implementation is responsible for this, >> > yeah, similar to ->write being responsible for invalidating around >> > O_DIRECT writes. >> > >> >> (and doesn't truncate_inode_pages_range handle page cache alignment >> >> anyway >> > >> > No, it bugs if given an end offset that isn't page aligned: >> > >> > BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1)); >> > >> > Lukas is working on a patch series to fix this: >> > >> > http://marc.info/?l=linux-fsdevel&m=136854986101843&w=2 >> > >> >> - and also why did btrfs use truncate_inode_pages_range instead >> >> of invalidate?) >> > >> > I'm not sure. Maybe they can have racing dirty pages and want them >> > thrown away rather than having invalidation fail? > > truncate_inode_pages_range ends with invalidate. It just locks the page > first and makes sure to wait for writeback if it was already in > progress. Does truncate_inode_pages_range(&inode->i_data, destoff, PAGE_CACHE_ALIGN(destoff + len) - 1); I also am worried about what does: 1) writing out data from start of previous page up to destoff (if destoff not page aligned, and first page dirty) 2) writing out data from dest+len through end of page (if destoff not page aligned, and last page dirty) before tossing first through last page out -- Thanks, Steve -- 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
