| Message ID | 20230519074047.1739879-6-dhowells@redhat.com (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | None | expand |
On Fri, May 19, 2023 at 08:40:20AM +0100, David Howells wrote: > +#ifdef CONFIG_FS_DAX > + if (IS_DAX(in->f_mapping->host)) No need for the ifdef. IS_DAX is compile-time false if CONFIG_FS_DAX is not set. A comment on why we're doing this in the code would probably be useful as well.
Christoph Hellwig <hch@infradead.org> wrote: > On Fri, May 19, 2023 at 08:40:20AM +0100, David Howells wrote: > > +#ifdef CONFIG_FS_DAX > > + if (IS_DAX(in->f_mapping->host)) > > No need for the ifdef. IS_DAX is compile-time false if CONFIG_FS_DAX > is not set. Ah - it's not that IS_DAX() is conditionalised, it's that S_DAX is. There's a bunch of places that use CONFIG_FS_DAX blocks, but I guess that's because they include calls to functions that are conditionalised out. I wonder if the dax_iomap_rw() declaration in the header can have a non-DAX fallback that returns an error and then we can get rid of some of the other conditionalisation. David
diff --git a/fs/splice.c b/fs/splice.c index 1e0b7c7038b5..7b818b5b18d4 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -421,6 +421,11 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, struct kiocb kiocb; int ret; +#ifdef CONFIG_FS_DAX + if (IS_DAX(in->f_mapping->host)) + return direct_splice_read(in, ppos, pipe, len, flags); +#endif + iov_iter_pipe(&to, ITER_DEST, pipe, len); init_sync_kiocb(&kiocb, in); kiocb.ki_pos = *ppos;
Make a read splice from a DAX file go directly to direct_splice_read() to do the reading as filemap_splice_read() is unlikely to find any pagecache to splice. I think this affects only erofs, Ext2, Ext4, fuse and XFS. Signed-off-by: David Howells <dhowells@redhat.com> cc: Christoph Hellwig <hch@lst.de> cc: Al Viro <viro@zeniv.linux.org.uk> cc: Jens Axboe <axboe@kernel.dk> cc: linux-erofs@lists.ozlabs.org cc: linux-ext4@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-xfs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-block@vger.kernel.org cc: linux-mm@kvack.org --- fs/splice.c | 5 +++++ 1 file changed, 5 insertions(+)