ext4: use locality group preallocation for small closed files

commit a9f2a2931d0e197ab28c6007966053fdababd53f upstream.

Curently we don't use any preallocation when a file is already closed
when allocating blocks (from writeback code when converting delayed
allocation). However for small files, using locality group preallocation
is actually desirable as that is not specific to a particular file.
Rather it is a method to pack small files together to reduce
fragmentation and for that the fact the file is closed is actually even
stronger hint the file would benefit from packing. So change the logic
to allow locality group preallocation in this case.

Fixes: 196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
CC: stable@kernel.org
Reported-and-tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/all/0d81a7c2-46b7-6010-62a4-3e6cfc1628d6@i2se.com/
Link: https://lore.kernel.org/r/20220908092136.11770-4-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 12 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 0623df52e440..0c7498a59943 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5169,6 +5169,7 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
 	int bsbits = ac->ac_sb->s_blocksize_bits;
 	loff_t size, isize;
+	bool inode_pa_eligible, group_pa_eligible;
 
 	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
 		return;
@@ -5176,25 +5177,27 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
 	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
 		return;
 
+	group_pa_eligible = sbi->s_mb_group_prealloc > 0;
+	inode_pa_eligible = true;
 	size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
 	isize = (i_size_read(ac->ac_inode) + ac->ac_sb->s_blocksize - 1)
 		>> bsbits;
 
+	/* No point in using inode preallocation for closed files */
 	if ((size == isize) && !ext4_fs_is_busy(sbi) &&
-	    !inode_is_open_for_write(ac->ac_inode)) {
-		ac->ac_flags |= EXT4_MB_HINT_NOPREALLOC;
-		return;
-	}
+	    !inode_is_open_for_write(ac->ac_inode))
+		inode_pa_eligible = false;
 
-	if (sbi->s_mb_group_prealloc <= 0) {
-		ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
-		return;
-	}
-
-	/* don't use group allocation for large files */
 	size = max(size, isize);
-	if (size > sbi->s_mb_stream_request) {
-		ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
+	/* Don't use group allocation for large files */
+	if (size > sbi->s_mb_stream_request)
+		group_pa_eligible = false;
+
+	if (!group_pa_eligible) {
+		if (inode_pa_eligible)
+			ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
+		else
+			ac->ac_flags |= EXT4_MB_HINT_NOPREALLOC;
 		return;
 	}