linux-kernel - [PATCH AUTOSEL 4.4 13/30] gfs2: Don't reject a supposedly full bitmap if we have blocks reserved

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Message-ID: <20180907003853.57942-13-alexander.levin@microsoft.com>
Date:   Fri, 7 Sep 2018 00:39:05 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Bob Peterson <rpeterso@...hat.com>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.4 13/30] gfs2: Don't reject a supposedly full bitmap
 if we have blocks reserved

From: Bob Peterson <rpeterso@...hat.com>

[ Upstream commit e79e0e1428188b24c3b57309ffa54a33c4ae40c4 ]

Before this patch, you could get into situations like this:

1. Process 1 searches for X free blocks, finds them, makes a reservation
2. Process 2 searches for free blocks in the same rgrp, but now the
   bitmap is full because process 1's reservation is skipped over.
   So it marks the bitmap as GBF_FULL.
3. Process 1 tries to allocate blocks from its own reservation, but
   since the GBF_FULL bit is set, it skips over the rgrp and searches
   elsewhere, thus not using its own reservation.

This patch adds an additional check to allow processes to use their
own reservations.

Signed-off-by: Bob Peterson <rpeterso@...hat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/gfs2/rgrp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index c134c0462cee..220f9f767307 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1691,7 +1691,8 @@ static int gfs2_rbm_find(struct gfs2_rbm *rbm, u8 state, u32 *minext,
 
 	while(1) {
 		bi = rbm_bi(rbm);
-		if (test_bit(GBF_FULL, &bi->bi_flags) &&
+		if ((ip == NULL || !gfs2_rs_active(&ip->i_res)) &&
+		    test_bit(GBF_FULL, &bi->bi_flags) &&
 		    (state == GFS2_BLKST_FREE))
 			goto next_bitmap;
 
-- 
2.17.1