[Linux-cachefs] [PATCH] ceph: clamp length of a read to CEPH_MSG_MAX_DATA_LEN

[Jeff Layton]

There's a hard limit on how large a read we can do from the OSD, defined
as CEPH_MSG_MAX_DATA_LEN (currently, 64M). It's possible to create a
file that is backed by larger objects than that (and indeed, xfstest
ceph/001 does just that).

Ensure we clamp the final length of a read to CEPH_MSG_MAX_DATA_LEN.

Signed-off-by: Jeff Layton <jlayton at kernel.org>
---
 fs/ceph/addr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

I'm likely going to fold this patch into the one that introduces
ceph_netfs_issue_op, so we don't have a regression in the series.

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 9939100f9f9d..ba459b15604d 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -212,7 +212,7 @@ static bool ceph_netfs_clamp_length(struct netfs_read_subrequest *subreq)
 	/* Truncate the extent at the end of the current block */
 	ceph_calc_file_object_mapping(&ci->i_layout, subreq->start, subreq->len,
 				      &objno, &objoff, &xlen);
-	subreq->len = xlen;
+	subreq->len = min(xlen, (u32)CEPH_MSG_MAX_DATA_LEN);
 	return true;
 }
 
-- 
2.31.1