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 <[email protected]>
fracktal · Jun 17, 2017 · 77e9ce3 · 77e9ce3
1 parent c0ef65d
commit 77e9ce3
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Showing 3 changed files with 17 additions and 16 deletions.
diff --git 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
@@ -1211,6 +1211,15 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
 
 	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
@@ -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;
 };
 
 /*