LU-16160 llite: SIGBUS is possible on a race with page reclaim

[fs/lustre-release.git] / lustre / llite / vvp_page.c

diff --git a/lustre/llite/vvp_page.c b/lustre/llite/vvp_page.c
index b892013..ccd228e 100644 (file)
--- a/lustre/llite/vvp_page.c
+++ b/lustre/llite/vvp_page.c
@@ -63,6 +63,41 @@ static void vvp_page_discard(const struct lu_env *env,
                ll_ra_stats_inc(vmpage->mapping->host, RA_STAT_DISCARDED);
 }
 
+static void vvp_page_delete(const struct lu_env *env,
+                           const struct cl_page_slice *slice)
+{
+       struct cl_page *cp = slice->cpl_page;
+
+       if (cp->cp_type == CPT_CACHEABLE) {
+               struct page *vmpage = cp->cp_vmpage;
+               struct inode *inode = vmpage->mapping->host;
+
+               LASSERT(PageLocked(vmpage));
+               LASSERT((struct cl_page *)vmpage->private == cp);
+
+               /* Drop the reference count held in vvp_page_init */
+               refcount_dec(&cp->cp_ref);
+
+               ClearPagePrivate(vmpage);
+               vmpage->private = 0;
+
+               /* clearpageuptodate prevents the page being read by the
+                * kernel after it has been deleted from Lustre, which avoids
+                * potential stale data reads.  The seqlock allows us to see
+                * that a page was potentially deleted and catch the resulting
+                * SIGBUS - see ll_filemap_fault() (LU-16160) */
+               write_seqlock(&ll_i2info(inode)->lli_page_inv_lock);
+               ClearPageUptodate(vmpage);
+               write_sequnlock(&ll_i2info(inode)->lli_page_inv_lock);
+
+               /*
+                * The reference from vmpage to cl_page is removed,
+                * but the reference back is still here. It is removed
+                * later in cl_page_free().
+                */
+       }
+}
+
 /**
  * Handles page transfer errors at VM level.
  *
@@ -159,6 +194,7 @@ static void vvp_page_completion_write(const struct lu_env *env,
 }
 
 static const struct cl_page_operations vvp_page_ops = {
+       .cpo_delete        = vvp_page_delete,
        .cpo_discard       = vvp_page_discard,
        .io = {
                [CRT_READ] = {