ext4: cache extent hole in extent status tree for ext4_da_map_blocks()

Currently extent status tree doesn't cache extent hole when a write
looks up in extent tree to make sure whether a block has been allocated
or not.  In this case, we don't put extent hole in extent cache because
later this extent might be removed and a new delayed extent might be
added back.  But it will cause a defect when we do a lot of writes.  If
we don't put extent hole in extent cache, the following writes also need
to access extent tree to look at whether or not a block has been
allocated.  It brings a cache miss.  This commit fixes this defect.
Also if the inode doesn't have any extent, this extent hole will be
cached as well.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

3 files changed, 19 insertions, 22 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 7b3f3b1decff..98da4cda9d18 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -556,10 +556,8 @@ enum {
 #define EXT4_GET_BLOCKS_KEEP_SIZE               0x0080
         /* Do not take i_data_sem locking in ext4_map_blocks */
 #define EXT4_GET_BLOCKS_NO_LOCK                 0x0100
-        /* Do not put hole in extent cache */
-#define EXT4_GET_BLOCKS_NO_PUT_HOLE             0x0200
         /* Convert written extents to unwritten */
-#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN       0x0400
+#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN       0x0200
 
 /*
  * The bit position of these flags must not overlap with any of the
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7ef2f11aca56..1ee24d74270f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2306,16 +2306,16 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
                                 ext4_lblk_t block)
 {
         int depth = ext_depth(inode);
-        unsigned long len = 0;
-        ext4_lblk_t lblock = 0;
+        ext4_lblk_t len;
+        ext4_lblk_t lblock;
         struct ext4_extent *ex;
+        struct extent_status es;
 
         ex = path[depth].p_ext;
         if (ex == NULL) {
-                /*
-                 * there is no extent yet, so gap is [0;-] and we
-                 * don't cache it
-                 */
+                /* there is no extent yet, so gap is [0;-] */
+                lblock = 0;
+                len = EXT_MAX_BLOCKS;
                 ext_debug("cache gap(whole file):");
         } else if (block < le32_to_cpu(ex->ee_block)) {
                 lblock = block;
@@ -2324,9 +2324,6 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
                                 block,
                                 le32_to_cpu(ex->ee_block),
                                  ext4_ext_get_actual_len(ex));
-                if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
-                        ext4_es_insert_extent(inode, lblock, len, ~0,
-                                              EXTENT_STATUS_HOLE);
         } else if (block >= le32_to_cpu(ex->ee_block)
                         + ext4_ext_get_actual_len(ex)) {
                 ext4_lblk_t next;
@@ -2340,14 +2337,19 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
                                 block);
                 BUG_ON(next == lblock);
                 len = next - lblock;
-                if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
-                        ext4_es_insert_extent(inode, lblock, len, ~0,
-                                              EXTENT_STATUS_HOLE);
         } else {
                 BUG();
         }
 
-        ext_debug(" -> %u:%lu\n", lblock, len);
+        ext4_es_find_delayed_extent_range(inode, lblock, lblock + len - 1, &es);
+        if (es.es_len) {
+                /* There's delayed extent containing lblock? */
+                if (es.es_lblk <= lblock)
+                        return;
+                len = min(es.es_lblk - lblock, len);
+        }
+        ext_debug(" -> %u:%u\n", lblock, len);
+        ext4_es_insert_extent(inode, lblock, len, ~0, EXTENT_STATUS_HOLE);
 }
 
 /*
@@ -4368,8 +4370,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
                  * put just found gap into cache to speed up
                  * subsequent requests
                  */
-                if ((flags & EXT4_GET_BLOCKS_NO_PUT_HOLE) == 0)
-                        ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
+                ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
                 goto out2;
         }
 
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2315e45161ee..d5a46a8df70b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1432,11 +1432,9 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
         if (ext4_has_inline_data(inode))
                 retval = 0;
         else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-                retval = ext4_ext_map_blocks(NULL, inode, map,
-                                             EXT4_GET_BLOCKS_NO_PUT_HOLE);
+                retval = ext4_ext_map_blocks(NULL, inode, map, 0);
         else
-                retval = ext4_ind_map_blocks(NULL, inode, map,
-                                             EXT4_GET_BLOCKS_NO_PUT_HOLE);
+                retval = ext4_ind_map_blocks(NULL, inode, map, 0);
 
 add_delayed:
         if (retval == 0) {