On 5/19/23 15:40, David Howells wrote:
Provide a splice_read stub for Ceph. This does the inode shutdown check
before proceeding and jumps to direct_splice_read() if O_DIRECT is set, 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 direct_splice_read() instead.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Xiubo Li <xiubli@xxxxxxxxxx>
cc: Ilya Dryomov <idryomov@xxxxxxxxx>
cc: Jeff Layton <jlayton@xxxxxxxxxx>
cc: ceph-devel@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
cc: linux-block@xxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
fs/ceph/file.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 65 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index f4d8bf7dec88..382dd5901748 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1745,6 +1745,70 @@ 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 ((in->f_flags & O_DIRECT) ||
+ ceph_has_inline_data(ci) ||
+ (fi->flags & CEPH_F_SYNC))
+ return direct_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) {
+ ceph_end_io_read(inode);
+ return ret;
+ }
+
+ 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_end_io_read(inode);
+ return direct_splice_read(in, ppos, pipe, len, flags);
Shouldn't we release cap ref before returning here ?
Thanks
- Xiubo
+ }
+
+ 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);
+
+ ceph_end_io_read(inode);
+ return ret;
+}
+
/*
* Take cap references to avoid releasing caps to MDS mid-write.
*
@@ -2593,7 +2657,7 @@ 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,
