[PATCH] ocfs2: fixing global bitmap allocating failure for discontig type

[Heming Zhao]

The commit 4eb7b93e0310 ("ocfs2: improve write IO performance when
fragmentation is high") introduced a regression. In the discontiguous
extent allocation case, ocfs2_cluster_group_search() is comparing with
the wrong target length, which causes allocation failure.

Call stack:
ocfs2_mkdir()
 ocfs2_reserve_new_inode()
  ocfs2_reserve_suballoc_bits()
   ocfs2_block_group_alloc()
    ocfs2_block_group_alloc_discontig()
     __ocfs2_claim_clusters()
      ocfs2_claim_suballoc_bits()
       ocfs2_search_chain()
        ocfs2_cluster_group_search()

Reported-by: Gautham Ananthakrishna <gautham.ananthakrishna@xxxxxxxxxx>
Fixes: 4eb7b93e0310 ("ocfs2: improve write IO performance when fragmentation is high")
Signed-off-by: Heming Zhao <heming.zhao@xxxxxxxx>
---
 fs/ocfs2/suballoc.c | 14 +++++++++++---
 fs/ocfs2/suballoc.h |  1 +
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index f7b483f0de2a..3dea082f6e91 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -698,10 +698,12 @@ static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
 
 	bg_bh = ocfs2_block_group_alloc_contig(osb, handle, alloc_inode,
 					       ac, cl);
-	if (PTR_ERR(bg_bh) == -ENOSPC)
+	if (PTR_ERR(bg_bh) == -ENOSPC) {
+		ac->ac_which = OCFS2_AC_USE_MAIN_DISCONTIG;
 		bg_bh = ocfs2_block_group_alloc_discontig(handle,
 							  alloc_inode,
 							  ac, cl);
+	}
 	if (IS_ERR(bg_bh)) {
 		status = PTR_ERR(bg_bh);
 		bg_bh = NULL;
@@ -2365,7 +2367,8 @@ int __ocfs2_claim_clusters(handle_t *handle,
 	BUG_ON(ac->ac_bits_given >= ac->ac_bits_wanted);
 
 	BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL
-	       && ac->ac_which != OCFS2_AC_USE_MAIN);
+	       && ac->ac_which != OCFS2_AC_USE_MAIN
+	       && ac->ac_which != OCFS2_AC_USE_MAIN_DISCONTIG);
 
 	if (ac->ac_which == OCFS2_AC_USE_LOCAL) {
 		WARN_ON(min_clusters > 1);
@@ -2427,7 +2430,12 @@ int ocfs2_claim_clusters(handle_t *handle,
 			 u32 *cluster_start,
 			 u32 *num_clusters)
 {
-	unsigned int bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
+	unsigned int bits_wanted;
+
+	if (ac->ac_which == OCFS2_AC_USE_MAIN)
+		bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
+	else /* ac_which == OCFS2_AC_USE_MAIN_DISCONTIG */
+		bits_wanted = min_clusters;
 
 	return __ocfs2_claim_clusters(handle, ac, min_clusters,
 				      bits_wanted, cluster_start, num_clusters);
diff --git a/fs/ocfs2/suballoc.h b/fs/ocfs2/suballoc.h
index b481b834857d..bcf2ed4a8631 100644
--- a/fs/ocfs2/suballoc.h
+++ b/fs/ocfs2/suballoc.h
@@ -29,6 +29,7 @@ struct ocfs2_alloc_context {
 #define OCFS2_AC_USE_MAIN  2
 #define OCFS2_AC_USE_INODE 3
 #define OCFS2_AC_USE_META  4
+#define OCFS2_AC_USE_MAIN_DISCONTIG  5
 	u32    ac_which;
 
 	/* these are used by the chain search */
-- 
2.43.0