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Commit b50c2de5 authored by Yan, Zheng's avatar Yan, Zheng Committed by Ilya Dryomov
Browse files

ceph: choose readdir frag based on previous readdir reply 



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: default avatar"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent e010dd0a

fs/ceph/dir.c

+12 −7
Original line number Diff line number Diff line
@@ -294,7 +294,7 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx) 
	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);
@@ -341,7 +341,6 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx) 
	/* 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;
@@ -352,6 +351,9 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx) 
		}



		if (is_hash_order(ctx->pos)) {

			/* 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 {
@@ -480,6 +482,7 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx) 
		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);
@@ -502,15 +505,17 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx) 
		ctx->pos++;

	}



	if (fi->next_offset > 2) {

	ceph_mdsc_put_request(fi->last_readdir);

	fi->last_readdir = NULL;



	if (fi->next_offset > 2) {

		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);