Revert "ext4: Stop trying writing pages if no free blocks generated"

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7CBCS
CVE: NA

--------------------------------

This reverts commit 07a8109d.

When ext4 runs out of space, there could be a potential data lost in
ext4_writepages:
If there are many preallocated blocks for some files, e4b bitmap is
different from block bitmap, and there are more free blocks accounted
by block bitmap.

    ext4_writepages                         P2
ext4_mb_new_blocks                  ext4_map_blocks
 ext4_mb_regular_allocator // No free bits in e4b bitmap
 ext4_mb_discard_preallocations_should_retry
  ext4_mb_discard_preallocations
   ext4_mb_discard_group_preallocations
    ext4_mb_release_inode_pa // updates e4b bitmap by pa->pa_free
     mb_free_blocks
                                     ext4_mb_new_blocks
                                      ext4_mb_regular_allocator
                                      // Got e4b bitmap's free bits
 ext4_mb_regular_allocator  // After 3 times retrying, ret ENOSPC

ext4_writepages
 mpage_map_and_submit_extent
  mpage_map_one_extent // ret ENOSPC
  if (err == -ENOSPC && EXT4_SB(sb)->s_mb_free_pending)
  // s_mb_free_pending is 0
  *give_up_on_write = true  // Abandon writeback, data lost!

Fixes: 07a8109d ("ext4: Stop trying writing pages if no free ...")
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>

fs/ext4/ext4.h

@@ -700,7 +700,6 @@ enum {
 #define EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER	0x0010
 #define EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER	0x0020
 #define EXT4_FREE_BLOCKS_RERESERVE_CLUSTER      0x0040
-#define EXT4_FREE_BLOCKS_DONT_WAIT_JOURNAL      0x0080
 
 /*
  * ioctl commands

fs/ext4/extents.c

@@ -1294,8 +1294,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
 			if (!ablocks[i])
 				continue;
 			ext4_free_blocks(handle, inode, NULL, ablocks[i], 1,
-					 EXT4_FREE_BLOCKS_METADATA |
-					 EXT4_FREE_BLOCKS_DONT_WAIT_JOURNAL);
+					 EXT4_FREE_BLOCKS_METADATA);
 		}
 	}
 	kfree(ablocks);
@@ -4330,7 +4329,6 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 			ext4_discard_preallocations(inode, 0);
 			if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
 				fb_flags = EXT4_FREE_BLOCKS_NO_QUOT_UPDATE;
-			fb_flags |= EXT4_FREE_BLOCKS_DONT_WAIT_JOURNAL;
 			ext4_free_blocks(handle, inode, NULL, newblock,
 					 EXT4_C2B(sbi, allocated_clusters),
 					 fb_flags);

fs/ext4/inode.c

@@ -2479,7 +2479,7 @@ static int mpage_map_and_submit_extent(handle_t *handle,
 			 * is non-zero, a commit should free up blocks.
 			 */
 			if ((err == -ENOMEM) ||
-			    (err == -ENOSPC && EXT4_SB(sb)->s_mb_free_pending)) {
+			    (err == -ENOSPC && ext4_count_free_clusters(sb))) {
 				if (progress)
 					goto update_disksize;
 				return err;

fs/ext4/mballoc.c

@@ -5498,9 +5498,8 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 	 * consistency guarantees.
 	 */
 	if (ext4_handle_valid(handle) &&
-	    (((flags & EXT4_FREE_BLOCKS_METADATA) ||
-	     !ext4_should_writeback_data(inode)) &&
-	     !(flags & EXT4_FREE_BLOCKS_DONT_WAIT_JOURNAL))) {
+	    ((flags & EXT4_FREE_BLOCKS_METADATA) ||
+	     !ext4_should_writeback_data(inode))) {
 		struct ext4_free_data *new_entry;
 		/*
 		 * We use __GFP_NOFAIL because ext4_free_blocks() is not allowed