| Message ID | 20210512075305.19048-1-johannes.thumshirn@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs-progs: check for minimal needed number of zones | expand |
On Wed, May 12, 2021 at 04:53:05PM +0900, Johannes Thumshirn wrote: > In order to create a usable zoned filesystem a minimum of 5 zones is > needed: > > - 2 zones for the 1st superblock > - 1 zone for the system block group > - 1 zone for a metadata block group > - 1 zone for a data block group > > Some tests in xfstests create a sized filesystem and depending on the zone > size of the underlying device, it may happen, that this filesystem is too > small to be used. It's better to not create a filesystem at all than to > create an unusable filesystem. Agreed, though there's no spare zone for relocation once any of them becomes unusable (which is a known problem and can happen for any zone count). Once this gets solved the limit will be increased accordingly.
On 12/05/2021 12:39, David Sterba wrote: > On Wed, May 12, 2021 at 04:53:05PM +0900, Johannes Thumshirn wrote: >> In order to create a usable zoned filesystem a minimum of 5 zones is >> needed: >> >> - 2 zones for the 1st superblock >> - 1 zone for the system block group >> - 1 zone for a metadata block group >> - 1 zone for a data block group >> >> Some tests in xfstests create a sized filesystem and depending on the zone >> size of the underlying device, it may happen, that this filesystem is too >> small to be used. It's better to not create a filesystem at all than to >> create an unusable filesystem. > > Agreed, though there's no spare zone for relocation once any of them > becomes unusable (which is a known problem and can happen for any zone > count). Once this gets solved the limit will be increased accordingly. > Indeed, I'm planning to have something like a 'global' reserve zone for relocation. Hope to get this done before the cut for v5.14.
On Wed, May 12, 2021 at 04:53:05PM +0900, Johannes Thumshirn wrote: > In order to create a usable zoned filesystem a minimum of 5 zones is > needed: > > - 2 zones for the 1st superblock > - 1 zone for the system block group > - 1 zone for a metadata block group > - 1 zone for a data block group > > Some tests in xfstests create a sized filesystem and depending on the zone > size of the underlying device, it may happen, that this filesystem is too > small to be used. It's better to not create a filesystem at all than to > create an unusable filesystem. We also want to think about reserved zones for regular superblocks. For example, with zone_size == 16M, we reserve zone #4 for regular superblock at 64MB, and this setup require one more zone to allocate a data block group. > Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> > --- > mkfs/main.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mkfs/main.c b/mkfs/main.c > index 104eead2cee8..a56d970f6362 100644 > --- a/mkfs/main.c > +++ b/mkfs/main.c > @@ -1283,6 +1283,14 @@ int BOX_MAIN(mkfs)(int argc, char **argv) > min_dev_size); > goto error; > } > + if (zoned && block_count && block_count < 5 * zone_size(file)) { > + error("size %llu is too small to make a usable filesystem", > + block_count); > + error("minimum size for a zoned btrfs filesystem is %llu", > + min_dev_size); This should be "5 * zone_size(file)". How about extending btrfs_min_dev_size() for zoned? Then, we can avoid repeating the size check code. > + goto error; > + } > + > for (i = saved_optind; i < saved_optind + dev_cnt; i++) { > char *path; > > -- > 2.31.1 >
On 12/05/2021 16:19, Naohiro Aota wrote: > On Wed, May 12, 2021 at 04:53:05PM +0900, Johannes Thumshirn wrote: >> In order to create a usable zoned filesystem a minimum of 5 zones is >> needed: >> >> - 2 zones for the 1st superblock >> - 1 zone for the system block group >> - 1 zone for a metadata block group >> - 1 zone for a data block group >> >> Some tests in xfstests create a sized filesystem and depending on the zone >> size of the underlying device, it may happen, that this filesystem is too >> small to be used. It's better to not create a filesystem at all than to >> create an unusable filesystem. > > We also want to think about reserved zones for regular > superblocks. For example, with zone_size == 16M, we reserve zone #4 > for regular superblock at 64MB, and this setup require one more zone > to allocate a data block group. > >> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> >> --- >> mkfs/main.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/mkfs/main.c b/mkfs/main.c >> index 104eead2cee8..a56d970f6362 100644 >> --- a/mkfs/main.c >> +++ b/mkfs/main.c >> @@ -1283,6 +1283,14 @@ int BOX_MAIN(mkfs)(int argc, char **argv) >> min_dev_size); >> goto error; >> } >> + if (zoned && block_count && block_count < 5 * zone_size(file)) { >> + error("size %llu is too small to make a usable filesystem", >> + block_count); >> + error("minimum size for a zoned btrfs filesystem is %llu", >> + min_dev_size); > > This should be "5 * zone_size(file)". > > How about extending btrfs_min_dev_size() for zoned? Then, we can avoid > repeating the size check code. I'll look into it.
diff --git a/mkfs/main.c b/mkfs/main.c index 104eead2cee8..a56d970f6362 100644 --- a/mkfs/main.c +++ b/mkfs/main.c @@ -1283,6 +1283,14 @@ int BOX_MAIN(mkfs)(int argc, char **argv) min_dev_size); goto error; } + if (zoned && block_count && block_count < 5 * zone_size(file)) { + error("size %llu is too small to make a usable filesystem", + block_count); + error("minimum size for a zoned btrfs filesystem is %llu", + min_dev_size); + goto error; + } + for (i = saved_optind; i < saved_optind + dev_cnt; i++) { char *path;
In order to create a usable zoned filesystem a minimum of 5 zones is needed: - 2 zones for the 1st superblock - 1 zone for the system block group - 1 zone for a metadata block group - 1 zone for a data block group Some tests in xfstests create a sized filesystem and depending on the zone size of the underlying device, it may happen, that this filesystem is too small to be used. It's better to not create a filesystem at all than to create an unusable filesystem. Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> --- mkfs/main.c | 8 ++++++++ 1 file changed, 8 insertions(+)