[lustre-devel] [PATCH 17/24] lustre: mdc: GET(X)ATTR to READPAGE portal

[James Simmons <jsimmons@infradead.org>]

From: Andreas Dilger <adilger@whamcloud.com>

Send the MDS_GETATTR and MDS_GETXATTR RPCs to the
MDS_READPAGE_PORTAL instead of the default portal to avoid
deadlocks with other MDS_REINT RPCs that may block all of
the MDS service threads on that portal.

This deadlock occurs with MDS_GETXATTR when selinux is
enabled, because getxattr becomes part of lookup, so it
takes a reference on a lock used for lookup.  However, all
of the MDS service threads on the default portal can be
consumed by threads waiting for that lock, resulting in
a deadlock when the getxattr can't be processed.

WC-bug-id: https://jira.whamcloud.com/browse/LU-15245
Lustre-commit: 5552eba1451d47ce1 ("LU-15245 mdc: GET(X)ATTR to READPAGE portal")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45593
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 fs/lustre/mdc/mdc_request.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/lustre/mdc/mdc_request.c b/fs/lustre/mdc/mdc_request.c
index 3284c01..1064d9f 100644
--- a/fs/lustre/mdc/mdc_request.c
+++ b/fs/lustre/mdc/mdc_request.c
@@ -224,6 +224,9 @@ static int mdc_getattr(struct obd_export *exp, struct md_op_data *op_data,
 		return rc;
 	}
 
+	/* LU-15245: avoid deadlock with modifying RPCs on MDS_REQUEST_PORTAL */
+	req->rq_request_portal = MDS_READPAGE_PORTAL;
+
 again:
 	mdc_pack_body(&req->rq_pill, &op_data->op_fid1, op_data->op_valid,
 		      op_data->op_mode, -1, 0);
@@ -402,6 +405,10 @@ static int mdc_xattr_common(struct obd_export *exp,
 	} else {
 		mdc_pack_body(&req->rq_pill, fid, valid, output_size,
 			      suppgid, flags);
+		/* Avoid deadlock with modifying RPCs on MDS_REQUEST_PORTAL.
+		 * See LU-15245.
+		 */
+		req->rq_request_portal = MDS_READPAGE_PORTAL;
 	}
 
 	if (xattr_name) {
-- 
1.8.3.1

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