[3.13.y-ckt stable] Patch "nfsd: don't halt scanning the DRC LRU list when there's an RC_INPROG entry" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    nfsd: don't halt scanning the DRC LRU list when there's an RC_INPROG entry

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From cb1df169719560bba386436e3a3d895d376da350 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton at primarydata.com>
Date: Thu, 5 Jun 2014 09:45:00 -0400
Subject: nfsd: don't halt scanning the DRC LRU list when there's an RC_INPROG
 entry

commit 1b19453d1c6abcfa7c312ba6c9f11a277568fc94 upstream.

Currently, the DRC cache pruner will stop scanning the list when it
hits an entry that is RC_INPROG. It's possible however for a call to
take a *very* long time. In that case, we don't want it to block other
entries from being pruned if they are expired or we need to trim the
cache to get back under the limit.

Fix the DRC cache pruner to just ignore RC_INPROG entries.

Signed-off-by: Jeff Layton <jlayton at primarydata.com>
Signed-off-by: J. Bruce Fields <bfields at redhat.com>
Cc: Joseph Salisbury <joseph.salisbury at canonical.com>
Reference: http://bugs.launchpad.net/bugs/1396065
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/nfsd/nfscache.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index f8f060f..6040da8 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -224,13 +224,6 @@ hash_refile(struct svc_cacherep *rp)
 	hlist_add_head(&rp->c_hash, cache_hash + hash_32(rp->c_xid, maskbits));
 }

-static inline bool
-nfsd_cache_entry_expired(struct svc_cacherep *rp)
-{
-	return rp->c_state != RC_INPROG &&
-	       time_after(jiffies, rp->c_timestamp + RC_EXPIRE);
-}
-
 /*
  * Walk the LRU list and prune off entries that are older than RC_EXPIRE.
  * Also prune the oldest ones when the total exceeds the max number of entries.
@@ -242,8 +235,14 @@ prune_cache_entries(void)
 	long freed = 0;

 	list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {
-		if (!nfsd_cache_entry_expired(rp) &&
-		    num_drc_entries <= max_drc_entries)
+		/*
+		 * Don't free entries attached to calls that are still
+		 * in-progress, but do keep scanning the list.
+		 */
+		if (rp->c_state == RC_INPROG)
+			continue;
+		if (num_drc_entries <= max_drc_entries &&
+		    time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
 			break;
 		nfsd_reply_cache_free_locked(rp);
 		freed++;
--
1.9.1