This is a note to let you know that I've just added the patch titled
ceph: choose readdir frag based on previous readdir reply
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ceph-choose-readdir-frag-based-on-previous-readdir-reply.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b50c2de51e611da90cf3cf04c058f7e9bbe79e93 Mon Sep 17 00:00:00 2001
From: "Yan, Zheng" <zyan@xxxxxxxxxx>
Date: Mon, 24 Apr 2017 11:56:50 +0800
Subject: ceph: choose readdir frag based on previous readdir reply
From: Yan, Zheng <zyan@xxxxxxxxxx>
commit b50c2de51e611da90cf3cf04c058f7e9bbe79e93 upstream.
The dirfragtree is lazily updated, it's not always accurate. Infinite
loops happens in following circumstance.
- client send request to read frag A
- frag A has been fragmented into frag B and C. So mds fills the reply
with contents of frag B
- client wants to read next frag C. ceph_choose_frag(frag value of C)
return frag A.
The fix is using previous readdir reply to calculate next readdir frag
when possible.
Signed-off-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ceph/dir.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -315,7 +315,7 @@ static int ceph_readdir(struct file *fil
struct ceph_mds_client *mdsc = fsc->mdsc;
int i;
int err;
- u32 ftype;
+ unsigned frag = -1;
struct ceph_mds_reply_info_parsed *rinfo;
dout("readdir %p file %p pos %llx\n", inode, file, ctx->pos);
@@ -362,7 +362,6 @@ more:
/* do we have the correct frag content buffered? */
if (need_send_readdir(fi, ctx->pos)) {
struct ceph_mds_request *req;
- unsigned frag;
int op = ceph_snap(inode) == CEPH_SNAPDIR ?
CEPH_MDS_OP_LSSNAP : CEPH_MDS_OP_READDIR;
@@ -373,8 +372,11 @@ more:
}
if (is_hash_order(ctx->pos)) {
- frag = ceph_choose_frag(ci, fpos_hash(ctx->pos),
- NULL, NULL);
+ /* fragtree isn't always accurate. choose frag
+ * based on previous reply when possible. */
+ if (frag == (unsigned)-1)
+ frag = ceph_choose_frag(ci, fpos_hash(ctx->pos),
+ NULL, NULL);
} else {
frag = fpos_frag(ctx->pos);
}
@@ -497,6 +499,7 @@ more:
struct ceph_mds_reply_dir_entry *rde = rinfo->dir_entries + i;
struct ceph_vino vino;
ino_t ino;
+ u32 ftype;
BUG_ON(rde->offset < ctx->pos);
@@ -519,15 +522,17 @@ more:
ctx->pos++;
}
+ ceph_mdsc_put_request(fi->last_readdir);
+ fi->last_readdir = NULL;
+
if (fi->next_offset > 2) {
- ceph_mdsc_put_request(fi->last_readdir);
- fi->last_readdir = NULL;
+ frag = fi->frag;
goto more;
}
/* more frags? */
if (!ceph_frag_is_rightmost(fi->frag)) {
- unsigned frag = ceph_frag_next(fi->frag);
+ frag = ceph_frag_next(fi->frag);
if (is_hash_order(ctx->pos)) {
loff_t new_pos = ceph_make_fpos(ceph_frag_value(frag),
fi->next_offset, true);
Patches currently in stable-queue which might be from zyan@xxxxxxxxxx are
queue-4.9/ceph-choose-readdir-frag-based-on-previous-readdir-reply.patch