From 77e9ce327d9b607cd6e57c0f4524a654dc59c4b1 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 17 Jun 2017 15:44:06 -0400
Subject: ufs: fix the logics for tail relocation

* original hysteresis loop got broken by typo back in 2002; now
it never switches out of OPTTIME state.  Fixed.
* critical levels for switching from OPTTIME to OPTSPACE and back
ought to be calculated once, at mount time.
* we should use mul_u64_u32_div() for those calculations, now that
->s_dsize is 64bit.
* to quote Kirk McKusick (in 1995 FreeBSD commit message):
    The threshold for switching from time-space and space-time is too small
    when minfree is 5%...so make it stay at space in this case.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/ufs/balloc.c | 22 ++++++----------------
 fs/ufs/super.c  |  9 +++++++++
 fs/ufs/ufs_fs.h |  2 ++
 3 files changed, 17 insertions(+), 16 deletions(-)

(limited to 'fs')

diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index 0315fea1d589..f80be4c5df9d 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -455,24 +455,14 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
 	/*
 	 * allocate new block and move data
 	 */
-	switch (fs32_to_cpu(sb, usb1->fs_optim)) {
-	    case UFS_OPTSPACE:
+	if (fs32_to_cpu(sb, usb1->fs_optim) == UFS_OPTSPACE) {
 		request = newcount;
-		if (uspi->s_minfree < 5 || uspi->cs_total.cs_nffree
-		    > uspi->s_dsize * uspi->s_minfree / (2 * 100))
-			break;
-		usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
-		break;
-	    default:
-		usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
-	
-	    case UFS_OPTTIME:
+		if (uspi->cs_total.cs_nffree < uspi->s_space_to_time)
+			usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
+	} else {
 		request = uspi->s_fpb;
-		if (uspi->cs_total.cs_nffree < uspi->s_dsize *
-		    (uspi->s_minfree - 2) / 100)
-			break;
-		usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
-		break;
+		if (uspi->cs_total.cs_nffree > uspi->s_time_to_space)
+			usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTSPACE);
 	}
 	result = ufs_alloc_fragments (inode, cgno, goal, request, err);
 	if (result) {
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 34656c7a8e22..f211b662dd92 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -1211,6 +1211,15 @@ magic_found:
 
 	uspi->s_root_blocks = mul_u64_u32_div(uspi->s_dsize,
 					      uspi->s_minfree, 100);
+	if (uspi->s_minfree <= 5) {
+		uspi->s_time_to_space = ~0ULL;
+		uspi->s_space_to_time = 0;
+		usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTSPACE);
+	} else {
+		uspi->s_time_to_space = (uspi->s_root_blocks / 2) + 1;
+		uspi->s_space_to_time = mul_u64_u32_div(uspi->s_dsize,
+					      uspi->s_minfree - 2, 100) - 1;
+	}
 
 	/*
 	 * Compute another frequently used values
diff --git a/fs/ufs/ufs_fs.h b/fs/ufs/ufs_fs.h
index 823d55a37586..150eef6f1233 100644
--- a/fs/ufs/ufs_fs.h
+++ b/fs/ufs/ufs_fs.h
@@ -792,6 +792,8 @@ struct ufs_sb_private_info {
 	__s32	fs_magic;       /* filesystem magic */
 	unsigned int s_dirblksize;
 	__u64   s_root_blocks;
+	__u64	s_time_to_space;
+	__u64	s_space_to_time;
 };
 
 /*
-- 
cgit