Make a read splice from a DAX file go directly to copy_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 <dhowe...@redhat.com> Reviewed-by: Christoph Hellwig <h...@lst.de> Reviewed-by: Christian Brauner <brau...@kernel.org> Reviewed-by: Theodore Ts'o <ty...@mit.edu> Reviewed-by: Gao Xiang <hsiang...@linux.alibaba.com> cc: Al Viro <v...@zeniv.linux.org.uk> cc: Jens Axboe <ax...@kernel.dk> cc: linux-erofs@lists.ozlabs.org cc: linux-e...@vger.kernel.org cc: linux-...@vger.kernel.org cc: linux-fsde...@vger.kernel.org cc: linux-bl...@vger.kernel.org cc: linux...@kvack.org --- Notes: ver #21) - Don't need #ifdef CONFIG_FS_DAX as IS_DAX() is false if !CONFIG_FS_DAX. - Needs to be in vfs_splice_read(), not generic_file_splice_read(). fs/splice.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index 76126b1aafcb..8268248df3a9 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -908,10 +908,10 @@ long vfs_splice_read(struct file *in, loff_t *ppos, if (unlikely(!in->f_op->splice_read)) return warn_unsupported(in, "read"); /* - * O_DIRECT doesn't deal with the pagecache, so we allocate a buffer, - * copy into it and splice that into the pipe. + * O_DIRECT and DAX don't deal with the pagecache, so we allocate a + * buffer, copy into it and splice that into the pipe. */ - if ((in->f_flags & O_DIRECT)) + if ((in->f_flags & O_DIRECT) || IS_DAX(in->f_mapping->host)) return copy_splice_read(in, ppos, pipe, len, flags); return in->f_op->splice_read(in, ppos, pipe, len, flags); }