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authorAbhi Das <adas@redhat.com>2015-04-08 17:03:56 +0300
committerBob Peterson <rpeterso@redhat.com>2015-04-08 17:31:18 +0300
commit30133177957dca9a3e2a37b720f891d3225a92a1 (patch)
tree67c0d0b540759a64ab10d84a222e5ef6a2c6671d /fs/gfs2/quota.c
parent7b4ddfa7c9523a19fca30830f8b426964d359da2 (diff)
downloadlinux-30133177957dca9a3e2a37b720f891d3225a92a1.tar.xz
gfs2: fix quota refresh race in do_glock()
quotad periodically syncs in-memory quotas to the ondisk quota file and sets the QDF_REFRESH flag so that a subsequent read of a synced quota is re-read from disk. gfs2_quota_lock() checks for this flag and sets a 'force' bit to force re-read from disk if requested. However, there is a race condition here. It is possible for gfs2_quota_lock() to find the QDF_REFRESH flag unset (i.e force=0) and quotad comes in immediately after and syncs the relevant quota and sets the QDF_REFRESH flag. gfs2_quota_lock() resumes with force=0 and uses the stale in-memory quota usage values that result in miscalculations. This patch fixes this race by moving the check for the QDF_REFRESH flag check further out into the gfs2_quota_lock() process, i.e, in do_glock(), under the protection of the quota glock. Signed-off-by: Abhi Das <adas@redhat.com> Signed-off-by: Bob Peterson <rpeterso@redhat.com> Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/quota.c')
-rw-r--r--fs/gfs2/quota.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 55614685a31c..5c27e48aa76f 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -923,6 +923,9 @@ restart:
if (error)
return error;
+ if (test_and_clear_bit(QDF_REFRESH, &qd->qd_flags))
+ force_refresh = FORCE;
+
qd->qd_qb = *(struct gfs2_quota_lvb *)qd->qd_gl->gl_lksb.sb_lvbptr;
if (force_refresh || qd->qd_qb.qb_magic != cpu_to_be32(GFS2_MAGIC)) {
@@ -974,11 +977,8 @@ int gfs2_quota_lock(struct gfs2_inode *ip, kuid_t uid, kgid_t gid)
sizeof(struct gfs2_quota_data *), sort_qd, NULL);
for (x = 0; x < ip->i_res->rs_qa_qd_num; x++) {
- int force = NO_FORCE;
qd = ip->i_res->rs_qa_qd[x];
- if (test_and_clear_bit(QDF_REFRESH, &qd->qd_flags))
- force = FORCE;
- error = do_glock(qd, force, &ip->i_res->rs_qa_qd_ghs[x]);
+ error = do_glock(qd, NO_FORCE, &ip->i_res->rs_qa_qd_ghs[x]);
if (error)
break;
}