[1/2] xfs_db: add inobtcnt upgrade path

Commit Message

Darrick J. Wong Jan. 9, 2021, 6:28 a.m. UTC

From: Darrick J. Wong <[e-mail]>

Enable users to upgrade their filesystems to support inode btree block
counters.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 db/sb.c              |   22 ++++++++++++++++++++++
 man/man8/xfs_admin.8 |    7 +++++++
 man/man8/xfs_db.8    |    3 +++
 3 files changed, 32 insertions(+)

Comments

Brian Foster Jan. 13, 2021, 6:35 p.m. UTC | #1

On Fri, Jan 08, 2021 at 10:28:25PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <[e-mail]>
> 
> Enable users to upgrade their filesystems to support inode btree block
> counters.
> 
> Signed-off-by: Darrick J. Wong <[e-mail]>
> ---

These two look Ok to me, but I noticed that both commands have weird
error semantics when run through xfs_admin and the associated features
are already set. E.g.:

# xfs_admin -O inobtcount /dev/test/tmp 
Upgrading V5 filesystem
Upgraded V5 filesystem.  Please run xfs_repair.
versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK,INOBTCNT
Running xfs_repair to ensure filesystem consistency.
# xfs_admin -O inobtcount /dev/test/tmp 
inode btree counter feature is already enabled
Running xfs_repair to ensure filesystem consistency.
Conversion failed, is the filesystem unmounted?
# mount /dev/test/tmp /mnt/
# umount /mnt/

So it looks like we run repair again the second time around even though
the bit was already set, which is probably unnecessary, but then also
for some reason report the result as failed.

(I also realized that repair is fixing up some agi metadata in this
case, so my previous thought around a special repair verify mode is
probably not relevant..).

Brian

>  db/sb.c              |   22 ++++++++++++++++++++++
>  man/man8/xfs_admin.8 |    7 +++++++
>  man/man8/xfs_db.8    |    3 +++
>  3 files changed, 32 insertions(+)
> 
> 
> diff --git a/db/sb.c b/db/sb.c
> index 93e4c405..b89ccdbe 100644
> --- a/db/sb.c
> +++ b/db/sb.c
> @@ -597,6 +597,7 @@ version_help(void)
>  " 'version attr2'    - enable v2 inline extended attributes\n"
>  " 'version log2'     - enable v2 log format\n"
>  " 'version needsrepair' - flag filesystem as requiring repair\n"
> +" 'version inobtcount' - enable inode btree counters\n"
>  "\n"
>  "The version function prints currently enabled features for a filesystem\n"
>  "according to the version field of its primary superblock.\n"
> @@ -857,6 +858,27 @@ version_f(
>  			}
>  
>  			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> +		} else if (!strcasecmp(argv[1], "inobtcount")) {
> +			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
> +				dbprintf(
> +		_("inode btree counter feature is already enabled\n"));
> +				exitcode = 1;
> +				return 1;
> +			}
> +			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
> +				dbprintf(
> +		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
> +				exitcode = 1;
> +				return 1;
> +			}
> +			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
> +				dbprintf(
> +		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
> +				exitcode = 1;
> +				return 1;
> +			}
> +
> +			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
>  		} else if (!strcasecmp(argv[1], "extflg")) {
>  			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
>  			case XFS_SB_VERSION_1:
> diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
> index b423981d..a776b375 100644
> --- a/man/man8/xfs_admin.8
> +++ b/man/man8/xfs_admin.8
> @@ -116,6 +116,13 @@ If this is a V5 filesystem, flag the filesystem as needing repairs.
>  Until
>  .BR xfs_repair (8)
>  is run, the filesystem will not be mountable.
> +.TP
> +.B inobtcount
> +Upgrade a V5 filesystem to support the inode btree counters feature.
> +This reduces mount time by caching the size of the inode btrees in the
> +allocation group metadata.
> +Once enabled, the filesystem will not be writable by older kernels.
> +The filesystem cannot be downgraded after this feature is enabled.
>  .RE
>  .TP
>  .BI \-U " uuid"
> diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> index 7331cf19..1b826e5d 100644
> --- a/man/man8/xfs_db.8
> +++ b/man/man8/xfs_db.8
> @@ -976,6 +976,9 @@ The filesystem can be flagged as requiring a run through
>  if the
>  .B needsrepair
>  option is specified and the filesystem is formatted with the V5 format.
> +Support for the inode btree counters feature can be enabled by using the
> +.B inobtcount
> +option if the filesystem is formatted with the V5 format.
>  .IP
>  If no argument is given, the current version and feature bits are printed.
>  With one argument, this command will write the updated version number
>

Darrick J. Wong Jan. 14, 2021, 1:08 a.m. UTC | #2

On Wed, Jan 13, 2021 at 01:35:05PM -0500, Brian Foster wrote:
> On Fri, Jan 08, 2021 at 10:28:25PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <[e-mail]>
> > 
> > Enable users to upgrade their filesystems to support inode btree block
> > counters.
> > 
> > Signed-off-by: Darrick J. Wong <[e-mail]>
> > ---
> 
> These two look Ok to me, but I noticed that both commands have weird
> error semantics when run through xfs_admin and the associated features
> are already set. E.g.:
> 
> # xfs_admin -O inobtcount /dev/test/tmp 
> Upgrading V5 filesystem
> Upgraded V5 filesystem.  Please run xfs_repair.
> versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK,INOBTCNT
> Running xfs_repair to ensure filesystem consistency.
> # xfs_admin -O inobtcount /dev/test/tmp 
> inode btree counter feature is already enabled
> Running xfs_repair to ensure filesystem consistency.
> Conversion failed, is the filesystem unmounted?
> # mount /dev/test/tmp /mnt/
> # umount /mnt/
> 
> So it looks like we run repair again the second time around even though
> the bit was already set, which is probably unnecessary, but then also
> for some reason report the result as failed.

Hm.  I guess I could define a second exitcode that means "no action
taken", and have xfs_admin exit.

> (I also realized that repair is fixing up some agi metadata in this
> case, so my previous thought around a special repair verify mode is
> probably not relevant..).

<nod>

--D

> Brian
> 
> >  db/sb.c              |   22 ++++++++++++++++++++++
> >  man/man8/xfs_admin.8 |    7 +++++++
> >  man/man8/xfs_db.8    |    3 +++
> >  3 files changed, 32 insertions(+)
> > 
> > 
> > diff --git a/db/sb.c b/db/sb.c
> > index 93e4c405..b89ccdbe 100644
> > --- a/db/sb.c
> > +++ b/db/sb.c
> > @@ -597,6 +597,7 @@ version_help(void)
> >  " 'version attr2'    - enable v2 inline extended attributes\n"
> >  " 'version log2'     - enable v2 log format\n"
> >  " 'version needsrepair' - flag filesystem as requiring repair\n"
> > +" 'version inobtcount' - enable inode btree counters\n"
> >  "\n"
> >  "The version function prints currently enabled features for a filesystem\n"
> >  "according to the version field of its primary superblock.\n"
> > @@ -857,6 +858,27 @@ version_f(
> >  			}
> >  
> >  			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> > +		} else if (!strcasecmp(argv[1], "inobtcount")) {
> > +			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
> > +				dbprintf(
> > +		_("inode btree counter feature is already enabled\n"));
> > +				exitcode = 1;
> > +				return 1;
> > +			}
> > +			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
> > +				dbprintf(
> > +		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
> > +				exitcode = 1;
> > +				return 1;
> > +			}
> > +			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
> > +				dbprintf(
> > +		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
> > +				exitcode = 1;
> > +				return 1;
> > +			}
> > +
> > +			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
> >  		} else if (!strcasecmp(argv[1], "extflg")) {
> >  			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
> >  			case XFS_SB_VERSION_1:
> > diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
> > index b423981d..a776b375 100644
> > --- a/man/man8/xfs_admin.8
> > +++ b/man/man8/xfs_admin.8
> > @@ -116,6 +116,13 @@ If this is a V5 filesystem, flag the filesystem as needing repairs.
> >  Until
> >  .BR xfs_repair (8)
> >  is run, the filesystem will not be mountable.
> > +.TP
> > +.B inobtcount
> > +Upgrade a V5 filesystem to support the inode btree counters feature.
> > +This reduces mount time by caching the size of the inode btrees in the
> > +allocation group metadata.
> > +Once enabled, the filesystem will not be writable by older kernels.
> > +The filesystem cannot be downgraded after this feature is enabled.
> >  .RE
> >  .TP
> >  .BI \-U " uuid"
> > diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> > index 7331cf19..1b826e5d 100644
> > --- a/man/man8/xfs_db.8
> > +++ b/man/man8/xfs_db.8
> > @@ -976,6 +976,9 @@ The filesystem can be flagged as requiring a run through
> >  if the
> >  .B needsrepair
> >  option is specified and the filesystem is formatted with the V5 format.
> > +Support for the inode btree counters feature can be enabled by using the
> > +.B inobtcount
> > +option if the filesystem is formatted with the V5 format.
> >  .IP
> >  If no argument is given, the current version and feature bits are printed.
> >  With one argument, this command will write the updated version number
> > 
>

Brian Foster Jan. 14, 2021, 9:40 a.m. UTC | #3

On Wed, Jan 13, 2021 at 05:08:35PM -0800, Darrick J. Wong wrote:
> On Wed, Jan 13, 2021 at 01:35:05PM -0500, Brian Foster wrote:
> > On Fri, Jan 08, 2021 at 10:28:25PM -0800, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <[e-mail]>
> > > 
> > > Enable users to upgrade their filesystems to support inode btree block
> > > counters.
> > > 
> > > Signed-off-by: Darrick J. Wong <[e-mail]>
> > > ---
> > 
> > These two look Ok to me, but I noticed that both commands have weird
> > error semantics when run through xfs_admin and the associated features
> > are already set. E.g.:
> > 
> > # xfs_admin -O inobtcount /dev/test/tmp 
> > Upgrading V5 filesystem
> > Upgraded V5 filesystem.  Please run xfs_repair.
> > versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK,INOBTCNT
> > Running xfs_repair to ensure filesystem consistency.
> > # xfs_admin -O inobtcount /dev/test/tmp 
> > inode btree counter feature is already enabled
> > Running xfs_repair to ensure filesystem consistency.
> > Conversion failed, is the filesystem unmounted?
> > # mount /dev/test/tmp /mnt/
> > # umount /mnt/
> > 
> > So it looks like we run repair again the second time around even though
> > the bit was already set, which is probably unnecessary, but then also
> > for some reason report the result as failed.
> 
> Hm.  I guess I could define a second exitcode that means "no action
> taken", and have xfs_admin exit.
> 

It's not totally clear to me what the expected flow is supposed to be if
a particular feature upgrade fails or is otherwise interrupted partway
through. If the expectation is for the user to rerun the xfs_admin
command, it might be worth making sure that we somehow or another fall
back through to repair when appropriate (whether it be unconditionally,
by checking if NEEDSREPAIR is still set, etc.)..

Brian

> > (I also realized that repair is fixing up some agi metadata in this
> > case, so my previous thought around a special repair verify mode is
> > probably not relevant..).
> 
> <nod>
> 
> --D
> 
> > Brian
> > 
> > >  db/sb.c              |   22 ++++++++++++++++++++++
> > >  man/man8/xfs_admin.8 |    7 +++++++
> > >  man/man8/xfs_db.8    |    3 +++
> > >  3 files changed, 32 insertions(+)
> > > 
> > > 
> > > diff --git a/db/sb.c b/db/sb.c
> > > index 93e4c405..b89ccdbe 100644
> > > --- a/db/sb.c
> > > +++ b/db/sb.c
> > > @@ -597,6 +597,7 @@ version_help(void)
> > >  " 'version attr2'    - enable v2 inline extended attributes\n"
> > >  " 'version log2'     - enable v2 log format\n"
> > >  " 'version needsrepair' - flag filesystem as requiring repair\n"
> > > +" 'version inobtcount' - enable inode btree counters\n"
> > >  "\n"
> > >  "The version function prints currently enabled features for a filesystem\n"
> > >  "according to the version field of its primary superblock.\n"
> > > @@ -857,6 +858,27 @@ version_f(
> > >  			}
> > >  
> > >  			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> > > +		} else if (!strcasecmp(argv[1], "inobtcount")) {
> > > +			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
> > > +				dbprintf(
> > > +		_("inode btree counter feature is already enabled\n"));
> > > +				exitcode = 1;
> > > +				return 1;
> > > +			}
> > > +			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
> > > +				dbprintf(
> > > +		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
> > > +				exitcode = 1;
> > > +				return 1;
> > > +			}
> > > +			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
> > > +				dbprintf(
> > > +		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
> > > +				exitcode = 1;
> > > +				return 1;
> > > +			}
> > > +
> > > +			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
> > >  		} else if (!strcasecmp(argv[1], "extflg")) {
> > >  			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
> > >  			case XFS_SB_VERSION_1:
> > > diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
> > > index b423981d..a776b375 100644
> > > --- a/man/man8/xfs_admin.8
> > > +++ b/man/man8/xfs_admin.8
> > > @@ -116,6 +116,13 @@ If this is a V5 filesystem, flag the filesystem as needing repairs.
> > >  Until
> > >  .BR xfs_repair (8)
> > >  is run, the filesystem will not be mountable.
> > > +.TP
> > > +.B inobtcount
> > > +Upgrade a V5 filesystem to support the inode btree counters feature.
> > > +This reduces mount time by caching the size of the inode btrees in the
> > > +allocation group metadata.
> > > +Once enabled, the filesystem will not be writable by older kernels.
> > > +The filesystem cannot be downgraded after this feature is enabled.
> > >  .RE
> > >  .TP
> > >  .BI \-U " uuid"
> > > diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> > > index 7331cf19..1b826e5d 100644
> > > --- a/man/man8/xfs_db.8
> > > +++ b/man/man8/xfs_db.8
> > > @@ -976,6 +976,9 @@ The filesystem can be flagged as requiring a run through
> > >  if the
> > >  .B needsrepair
> > >  option is specified and the filesystem is formatted with the V5 format.
> > > +Support for the inode btree counters feature can be enabled by using the
> > > +.B inobtcount
> > > +option if the filesystem is formatted with the V5 format.
> > >  .IP
> > >  If no argument is given, the current version and feature bits are printed.
> > >  With one argument, this command will write the updated version number
> > > 
> > 
>

Darrick J. Wong Jan. 15, 2021, 8:40 p.m. UTC | #4

On Thu, Jan 14, 2021 at 04:40:57AM -0500, Brian Foster wrote:
> On Wed, Jan 13, 2021 at 05:08:35PM -0800, Darrick J. Wong wrote:
> > On Wed, Jan 13, 2021 at 01:35:05PM -0500, Brian Foster wrote:
> > > On Fri, Jan 08, 2021 at 10:28:25PM -0800, Darrick J. Wong wrote:
> > > > From: Darrick J. Wong <[e-mail]>
> > > > 
> > > > Enable users to upgrade their filesystems to support inode btree block
> > > > counters.
> > > > 
> > > > Signed-off-by: Darrick J. Wong <[e-mail]>
> > > > ---
> > > 
> > > These two look Ok to me, but I noticed that both commands have weird
> > > error semantics when run through xfs_admin and the associated features
> > > are already set. E.g.:
> > > 
> > > # xfs_admin -O inobtcount /dev/test/tmp 
> > > Upgrading V5 filesystem
> > > Upgraded V5 filesystem.  Please run xfs_repair.
> > > versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK,INOBTCNT
> > > Running xfs_repair to ensure filesystem consistency.
> > > # xfs_admin -O inobtcount /dev/test/tmp 
> > > inode btree counter feature is already enabled
> > > Running xfs_repair to ensure filesystem consistency.
> > > Conversion failed, is the filesystem unmounted?
> > > # mount /dev/test/tmp /mnt/
> > > # umount /mnt/
> > > 
> > > So it looks like we run repair again the second time around even though
> > > the bit was already set, which is probably unnecessary, but then also
> > > for some reason report the result as failed.
> > 
> > Hm.  I guess I could define a second exitcode that means "no action
> > taken", and have xfs_admin exit.
> > 
> 
> It's not totally clear to me what the expected flow is supposed to be if
> a particular feature upgrade fails or is otherwise interrupted partway
> through.

Me neither.  But let me try to work through some outcomes:

Upgrade succeeds -- xfs_db returns 0, needsrepair is set, repair runs
Cannot upgrade -- xfs_db returns 2, fs untouched
Feature already set -- xfs_db returns 2, fs untouched
FS corrupt -- xfs_db returns 1, fs untouched, repair runs
primary super write fails -- xfs_db returns 1, fs untouched, repair runs
secondary sb write fails -- xfs_db returns 1, primary super has
			    needsrepair set, repair runs

Does that seem thorough enough?  That's, uh, what the code in my dev
tree does now.  Will send out a v++ in a bit.

> If the expectation is for the user to rerun the xfs_admin
> command, it might be worth making sure that we somehow or another fall
> back through to repair when appropriate (whether it be unconditionally,
> by checking if NEEDSREPAIR is still set, etc.)..

My expectation is that if xfs_db fails, the admin should run xfs_repair
to fix anything that's wrong with the fs.  Maybe they can skip that if
the primary super write fails with EIO, but that's up to the sysadmin's
judgment.

--D

> Brian
> 
> > > (I also realized that repair is fixing up some agi metadata in this
> > > case, so my previous thought around a special repair verify mode is
> > > probably not relevant..).
> > 
> > <nod>
> > 
> > --D
> > 
> > > Brian
> > > 
> > > >  db/sb.c              |   22 ++++++++++++++++++++++
> > > >  man/man8/xfs_admin.8 |    7 +++++++
> > > >  man/man8/xfs_db.8    |    3 +++
> > > >  3 files changed, 32 insertions(+)
> > > > 
> > > > 
> > > > diff --git a/db/sb.c b/db/sb.c
> > > > index 93e4c405..b89ccdbe 100644
> > > > --- a/db/sb.c
> > > > +++ b/db/sb.c
> > > > @@ -597,6 +597,7 @@ version_help(void)
> > > >  " 'version attr2'    - enable v2 inline extended attributes\n"
> > > >  " 'version log2'     - enable v2 log format\n"
> > > >  " 'version needsrepair' - flag filesystem as requiring repair\n"
> > > > +" 'version inobtcount' - enable inode btree counters\n"
> > > >  "\n"
> > > >  "The version function prints currently enabled features for a filesystem\n"
> > > >  "according to the version field of its primary superblock.\n"
> > > > @@ -857,6 +858,27 @@ version_f(
> > > >  			}
> > > >  
> > > >  			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> > > > +		} else if (!strcasecmp(argv[1], "inobtcount")) {
> > > > +			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
> > > > +				dbprintf(
> > > > +		_("inode btree counter feature is already enabled\n"));
> > > > +				exitcode = 1;
> > > > +				return 1;
> > > > +			}
> > > > +			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
> > > > +				dbprintf(
> > > > +		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
> > > > +				exitcode = 1;
> > > > +				return 1;
> > > > +			}
> > > > +			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
> > > > +				dbprintf(
> > > > +		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
> > > > +				exitcode = 1;
> > > > +				return 1;
> > > > +			}
> > > > +
> > > > +			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
> > > >  		} else if (!strcasecmp(argv[1], "extflg")) {
> > > >  			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
> > > >  			case XFS_SB_VERSION_1:
> > > > diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
> > > > index b423981d..a776b375 100644
> > > > --- a/man/man8/xfs_admin.8
> > > > +++ b/man/man8/xfs_admin.8
> > > > @@ -116,6 +116,13 @@ If this is a V5 filesystem, flag the filesystem as needing repairs.
> > > >  Until
> > > >  .BR xfs_repair (8)
> > > >  is run, the filesystem will not be mountable.
> > > > +.TP
> > > > +.B inobtcount
> > > > +Upgrade a V5 filesystem to support the inode btree counters feature.
> > > > +This reduces mount time by caching the size of the inode btrees in the
> > > > +allocation group metadata.
> > > > +Once enabled, the filesystem will not be writable by older kernels.
> > > > +The filesystem cannot be downgraded after this feature is enabled.
> > > >  .RE
> > > >  .TP
> > > >  .BI \-U " uuid"
> > > > diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> > > > index 7331cf19..1b826e5d 100644
> > > > --- a/man/man8/xfs_db.8
> > > > +++ b/man/man8/xfs_db.8
> > > > @@ -976,6 +976,9 @@ The filesystem can be flagged as requiring a run through
> > > >  if the
> > > >  .B needsrepair
> > > >  option is specified and the filesystem is formatted with the V5 format.
> > > > +Support for the inode btree counters feature can be enabled by using the
> > > > +.B inobtcount
> > > > +option if the filesystem is formatted with the V5 format.
> > > >  .IP
> > > >  If no argument is given, the current version and feature bits are printed.
> > > >  With one argument, this command will write the updated version number
> > > > 
> > > 
> > 
>

Patch

diff --git a/db/sb.c b/db/sb.c
index 93e4c405..b89ccdbe 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -597,6 +597,7 @@  version_help(void)
 " 'version attr2'    - enable v2 inline extended attributes\n"
 " 'version log2'     - enable v2 log format\n"
 " 'version needsrepair' - flag filesystem as requiring repair\n"
+" 'version inobtcount' - enable inode btree counters\n"
 "\n"
 "The version function prints currently enabled features for a filesystem\n"
 "according to the version field of its primary superblock.\n"
@@ -857,6 +858,27 @@  version_f(
 			}
 
 			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
+		} else if (!strcasecmp(argv[1], "inobtcount")) {
+			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature is already enabled\n"));
+				exitcode = 1;
+				return 1;
+			}
+			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
+				exitcode = 1;
+				return 1;
+			}
+			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
+				exitcode = 1;
+				return 1;
+			}
+
+			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
 		} else if (!strcasecmp(argv[1], "extflg")) {
 			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
 			case XFS_SB_VERSION_1:
diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
index b423981d..a776b375 100644
--- a/man/man8/xfs_admin.8
+++ b/man/man8/xfs_admin.8
@@ -116,6 +116,13 @@  If this is a V5 filesystem, flag the filesystem as needing repairs.
 Until
 .BR xfs_repair (8)
 is run, the filesystem will not be mountable.
+.TP
+.B inobtcount
+Upgrade a V5 filesystem to support the inode btree counters feature.
+This reduces mount time by caching the size of the inode btrees in the
+allocation group metadata.
+Once enabled, the filesystem will not be writable by older kernels.
+The filesystem cannot be downgraded after this feature is enabled.
 .RE
 .TP
 .BI \-U " uuid"
diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index 7331cf19..1b826e5d 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -976,6 +976,9 @@  The filesystem can be flagged as requiring a run through
 if the
 .B needsrepair
 option is specified and the filesystem is formatted with the V5 format.
+Support for the inode btree counters feature can be enabled by using the
+.B inobtcount
+option if the filesystem is formatted with the V5 format.
 .IP
 If no argument is given, the current version and feature bits are printed.
 With one argument, this command will write the updated version number