Messages in this thread | | | Date | Mon, 22 May 2023 10:12:49 +0800 | Subject | Re: [PATCH v21 16/30] ceph: Provide a splice-read stub | From | Xiubo Li <> |
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On 5/20/23 08:00, David Howells wrote: > Provide a splice_read stub for Ceph. This does the inode shutdown check > before proceeding and jumps to copy_splice_read() if the file has inline > data or is a synchronous file. > > We try and get FILE_RD and either FILE_CACHE and/or FILE_LAZYIO caps and > hold them across filemap_splice_read(). If we fail to get FILE_CACHE or > FILE_LAZYIO capabilities, we use copy_splice_read() instead. > > 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: Xiubo Li <xiubli@redhat.com> > cc: Ilya Dryomov <idryomov@gmail.com> > cc: Jeff Layton <jlayton@kernel.org> > cc: ceph-devel@vger.kernel.org > cc: linux-fsdevel@vger.kernel.org > cc: linux-block@vger.kernel.org > cc: linux-mm@kvack.org > --- > > Notes: > ver #21) > - Need to drop the caps ref. > - O_DIRECT is handled by the caller. > > fs/ceph/file.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 64 insertions(+), 1 deletion(-) > > diff --git a/fs/ceph/file.c b/fs/ceph/file.c > index f4d8bf7dec88..4285f6cb5d3b 100644 > --- a/fs/ceph/file.c > +++ b/fs/ceph/file.c > @@ -1745,6 +1745,69 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to) > return ret; > } > > +/* > + * Wrap filemap_splice_read with checks for cap bits on the inode. > + * Atomically grab references, so that those bits are not released > + * back to the MDS mid-read. > + */ > +static ssize_t ceph_splice_read(struct file *in, loff_t *ppos, > + struct pipe_inode_info *pipe, > + size_t len, unsigned int flags) > +{ > + struct ceph_file_info *fi = in->private_data; > + struct inode *inode = file_inode(in); > + struct ceph_inode_info *ci = ceph_inode(inode); > + ssize_t ret; > + int want = 0, got = 0; > + CEPH_DEFINE_RW_CONTEXT(rw_ctx, 0); > + > + dout("splice_read %p %llx.%llx %llu~%zu trying to get caps on %p\n", > + inode, ceph_vinop(inode), *ppos, len, inode); > + > + if (ceph_inode_is_shutdown(inode)) > + return -ESTALE; > + > + if (ceph_has_inline_data(ci) || > + (fi->flags & CEPH_F_SYNC)) > + return copy_splice_read(in, ppos, pipe, len, flags); > + > + ceph_start_io_read(inode); > + > + want = CEPH_CAP_FILE_CACHE; > + if (fi->fmode & CEPH_FILE_MODE_LAZY) > + want |= CEPH_CAP_FILE_LAZYIO; > + > + ret = ceph_get_caps(in, CEPH_CAP_FILE_RD, want, -1, &got); > + if (ret < 0) > + goto out_end; > + > + if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) == 0) { > + dout("splice_read/sync %p %llx.%llx %llu~%zu got cap refs on %s\n", > + inode, ceph_vinop(inode), *ppos, len, > + ceph_cap_string(got)); > + > + ceph_put_cap_refs(ci, got); > + ceph_end_io_read(inode); > + return copy_splice_read(in, ppos, pipe, len, flags); > + } > + > + dout("splice_read %p %llx.%llx %llu~%zu got cap refs on %s\n", > + inode, ceph_vinop(inode), *ppos, len, ceph_cap_string(got)); > + > + rw_ctx.caps = got; > + ceph_add_rw_context(fi, &rw_ctx); > + ret = filemap_splice_read(in, ppos, pipe, len, flags); > + ceph_del_rw_context(fi, &rw_ctx); > + > + dout("splice_read %p %llx.%llx dropping cap refs on %s = %zd\n", > + inode, ceph_vinop(inode), ceph_cap_string(got), ret); > + > + ceph_put_cap_refs(ci, got); > +out_end: > + ceph_end_io_read(inode); > + return ret; > +} > + > /* > * Take cap references to avoid releasing caps to MDS mid-write. > * > @@ -2593,7 +2656,7 @@ const struct file_operations ceph_file_fops = { > .lock = ceph_lock, > .setlease = simple_nosetlease, > .flock = ceph_flock, > - .splice_read = generic_file_splice_read, > + .splice_read = ceph_splice_read, > .splice_write = iter_file_splice_write, > .unlocked_ioctl = ceph_ioctl, > .compat_ioctl = compat_ptr_ioctl, > LGTM.
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Thanks
- Xiubo
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