On Fri 23-07-21 22:58:40, Andreas Gruenbacher wrote: > Also disable page faults during direct I/O requests and implement the same kind > of retry logic as in the buffered I/O case. > > Direct I/O requests differ from buffered I/O requests in that they use > bio_iov_iter_get_pages for grabbing page references and faulting in pages > instead of triggering real page faults. Those manual page faults can be > disabled with the iocb->noio flag. > > Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> > --- > fs/gfs2/file.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) > > diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c > index f66ac7f56f6d..7986f3be69d2 100644 > --- a/fs/gfs2/file.c > +++ b/fs/gfs2/file.c > @@ -782,21 +782,41 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to, > struct file *file = iocb->ki_filp; > struct gfs2_inode *ip = GFS2_I(file->f_mapping->host); > size_t count = iov_iter_count(to); > + size_t written = 0; > ssize_t ret; > > + /* > + * In this function, we disable page faults when we're holding the > + * inode glock while doing I/O. If a page fault occurs, we drop the > + * inode glock, fault in the pages manually, and then we retry. Other > + * than in gfs2_file_read_iter, iomap_dio_rw can trigger implicit as > + * well as manual page faults, and we need to disable both kinds > + * separately. > + */ > + > if (!count) > return 0; /* skip atime */ > > gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, gh); > +retry: > ret = gfs2_glock_nq(gh); > if (ret) > goto out_uninit; > > + pagefault_disable(); Is there any use in pagefault_disable() here? iomap_dio_rw() should not trigger any page faults anyway, should it? Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
