f2fs: reorganize f2fs_map_blocks

In this patch, we try to reorganize f2fs_map_blocks to make block mapping
flow more clear by using following structure:

/* check status of mapping */

if (unmapped) {
	/* blkaddr == NULL_ADDR || blkaddr == NEW_ADDR */

	if (create) {
		/* write path, handle dio write case here */
		alloc_and_map;
	} else {
		/*
		 * handle read cases from all call paths:
		 *     1. generic read;
		 *     2. dio read;
		 *     3. fiemap;
		 *     4. bmap
		 */
	}
}

/* map buffer_header */

Besides, this patch handles the missing case correctly for dio write:
When we fail in __allocate_data_blocks, then in f2fs_map_blocks, we will
not allocate blocks correctly for preallocated blocks, but returning with
an unmapped buffer head, which will result in failure of dio write.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 681373e1da9295e63c4ff9ebc7fec88ca4f65755..883b6499841f1ad2c979b9a77bcd9e46212ee09b 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -596,40 +596,36 @@ static int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
                        err = 0;
                goto unlock_out;
        }
-       if (dn.data_blkaddr == NEW_ADDR) {
-               if (flag == F2FS_GET_BLOCK_BMAP) {
-                       err = -ENOENT;
-                       goto put_out;
-               } else if (flag == F2FS_GET_BLOCK_READ ||
-                               flag == F2FS_GET_BLOCK_DIO) {
-                       goto put_out;
+
+       if (dn.data_blkaddr == NEW_ADDR || dn.data_blkaddr == NULL_ADDR) {
+               if (create) {
+                       err = __allocate_data_block(&dn);
+                       if (err)
+                               goto put_out;
+                       allocated = true;
+                       map->m_flags = F2FS_MAP_NEW;
+               } else {
+                       if (flag != F2FS_GET_BLOCK_FIEMAP ||
+                                               dn.data_blkaddr != NEW_ADDR) {
+                               if (flag == F2FS_GET_BLOCK_BMAP)
+                                       err = -ENOENT;
+                               goto put_out;
+                       }
+
+                       /*
+                        * preallocated unwritten block should be mapped
+                        * for fiemap.
+                        */
+                       if (dn.data_blkaddr == NEW_ADDR)
+                               map->m_flags = F2FS_MAP_UNWRITTEN;
                }
-               /*
-                * if it is in fiemap call path (flag = F2FS_GET_BLOCK_FIEMAP),
-                * mark it as mapped and unwritten block.
-                */
        }
 
-       if (dn.data_blkaddr != NULL_ADDR) {
-               map->m_flags = F2FS_MAP_MAPPED;
-               map->m_pblk = dn.data_blkaddr;
-               if (dn.data_blkaddr == NEW_ADDR)
-                       map->m_flags |= F2FS_MAP_UNWRITTEN;
-       } else if (create) {
-               err = __allocate_data_block(&dn);
-               if (err)
-                       goto put_out;
-               allocated = true;
-               map->m_flags = F2FS_MAP_NEW | F2FS_MAP_MAPPED;
-               map->m_pblk = dn.data_blkaddr;
-       } else {
-               if (flag == F2FS_GET_BLOCK_BMAP)
-                       err = -ENOENT;
-               goto put_out;
-       }
+       map->m_flags |= F2FS_MAP_MAPPED;
+       map->m_pblk = dn.data_blkaddr;
+       map->m_len = 1;
 
        end_offset = ADDRS_PER_PAGE(dn.node_page, F2FS_I(inode));
-       map->m_len = 1;
        dn.ofs_in_node++;
        pgofs++;
 
@@ -648,23 +644,31 @@ get_next:
                        goto unlock_out;
                }
 
-               if (dn.data_blkaddr == NEW_ADDR &&
-                               flag != F2FS_GET_BLOCK_FIEMAP)
-                       goto put_out;
-
                end_offset = ADDRS_PER_PAGE(dn.node_page, F2FS_I(inode));
        }
 
        if (maxblocks > map->m_len) {
                block_t blkaddr = datablock_addr(dn.node_page, dn.ofs_in_node);
-               if (blkaddr == NULL_ADDR && create) {
-                       err = __allocate_data_block(&dn);
-                       if (err)
-                               goto sync_out;
-                       allocated = true;
-                       map->m_flags |= F2FS_MAP_NEW;
-                       blkaddr = dn.data_blkaddr;
+
+               if (blkaddr == NEW_ADDR || blkaddr == NULL_ADDR) {
+                       if (create) {
+                               err = __allocate_data_block(&dn);
+                               if (err)
+                                       goto sync_out;
+                               allocated = true;
+                               map->m_flags |= F2FS_MAP_NEW;
+                               blkaddr = dn.data_blkaddr;
+                       } else {
+                               /*
+                                * we only merge preallocated unwritten blocks
+                                * for fiemap.
+                                */
+                               if (flag != F2FS_GET_BLOCK_FIEMAP ||
+                                               blkaddr != NEW_ADDR)
+                                       goto sync_out;
+                       }
                }
+
                /* Give more consecutive addresses for the readahead */
                if ((map->m_pblk != NEW_ADDR &&
                                blkaddr == (map->m_pblk + ofs)) ||