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ufs: fix the logics for tail relocation

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* 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>
This commit is contained in:
Al Viro 2017-06-17 15:44:06 -04:00
parent c0ef65d292
commit 77e9ce327d
3 changed files with 17 additions and 16 deletions
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22
fs/ufs/balloc.c
View file

@ -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) {

9
fs/ufs/super.c
View file

@ -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

2
fs/ufs/ufs_fs.h
View file

@ -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;
};
/*