Re: [PATCH] xfs_quota: fix -d option to limit directory depth correctly

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jun 15, 2018 at 01:44:49PM +0200, Carlos Maiolino wrote:
> Although the patch looks correct, the patch description/subject is confusing
> IMHO.
> 
> On Mon, Jun 11, 2018 at 05:39:59AM +0000, Kazuya Mio wrote:
> 
> > xfs_quota -x -c "project -d DEPTH" stops in the middle of its operation
> > if a directory whose level is more than DEPTH was found.
> > 
> 
> > To set/check/clear a project quota, xfs_quota performs pre-order tree traversal
> > by using nftw(3). However, if the directory whose level is more than
> > the recursion level specified by -d option is found, the function called
> > by nftw() returns -1 and nftw() stops the tree walk.
> > 
> 
> I've got what you meant here, but in fact, this description just sounds to me
> as the operation should work, i.e. stop when DEPTH is hit.
> 
> What you think about something like:
> 
> ====
> Continue the file tree walk, even though DEPTH is hit in one or more
> sub-directory tree(s), so all sub-directory trees are processed up to DEPTH
> 
> To set/check/clear a project quota, xfs_quota performs pre-order tree traversal
> by using nftw(3). However, by now, {check,setup,clear}_project, returns -1 when
> DEPTH is hit, stopping the directory tree walk.
> 
> Change the return value of these functions to 0, when DEPTH is hit, so, the
> remaining sub-directory trees are also processed up to DEPTH.

I suggest contrasting the current behavior vs. the documented behavior a
little more explicitly:

"To set/check/clear a project quota, xfs_quota performs a pre-order tree
traversal by using nftw(3).  The documentation states that the -d option
can be used to skip subtrees below a certain level in the directory
hierarchy.  Unfortunately, {check,setup,clear}_project returns -1 when
DEPTH is hit, which stops the directory tree walk immediately.  We only
wanted to skip the subtree, so return 0 instead."

Though if we're going to use FTW_ACTIONRETVAL/FTW_SKIP_SUBTREE then
there ought to be checks for the existence of those flags at build time.

--D

> ====
> 
> But well, English is not my native language too, so, might be more useful if some
> native English speaker commented on it.
> 
> For the patch itself:
> 
> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
> 
> 
> > The following steps show that only one directory is set a project quota,
> > even though another directory whose level is the same as the recursion level
> > isn't set a project quota.
> > 
> 
> > # mkfs.xfs -f /dev/sdb1
> > # mount -o pquota /dev/sdb1 /mnt
> > # mkdir -p /mnt/pquota/dirA/dirAA /mnt/pquota/dirB/dirBB
> > # xfs_quota -x -c "project -d 1 -s -p /mnt/pquota 100" 
> > # xfs_io -c stat /mnt/pquota/dirA | grep projid
> > fsxattr.projid = 100
> > # xfs_io -c stat /mnt/pquota/dirB | grep projid
> > fsxattr.projid = 0
> > 
> > To fix above problem, if the directory whose level is more than the recursion
> > level is found, the function called by nftw() returns 0 instead of -1.
> > 
> > Note that the time of tree traversal is the same as no limitation of
> > recursion level. To reduce the time, we have to use FTW_SKIP_SUBTREE
> > that is glibc-specified flag. Is it better to use this flag?
> > 
> > Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
> > ---
> >  quota/project.c |    6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > diff --git a/quota/project.c b/quota/project.c
> > index e4e7a01..20bc01b 100644
> > --- a/quota/project.c
> > +++ b/quota/project.c
> > @@ -101,7 +101,7 @@ check_project(
> >  	int			fd;
> >  
> >  	if (recurse_depth >= 0 && data->level > recurse_depth)
> > -		return -1;
> > +		return 0;
> >  
> >  	if (flag == FTW_NS ){
> >  		exitcode = 1;
> > @@ -146,7 +146,7 @@ clear_project(
> >  	int			fd;
> >  
> >  	if (recurse_depth >= 0 && data->level > recurse_depth)
> > -		return -1;
> > +		return 0;
> >  
> >  	if (flag == FTW_NS ){
> >  		exitcode = 1;
> > @@ -193,7 +193,7 @@ setup_project(
> >  	int			fd;
> >  
> >  	if (recurse_depth >= 0 && data->level > recurse_depth)
> > -		return -1;
> > +		return 0;
> >  
> >  	if (flag == FTW_NS ){
> >  		exitcode = 1;
> > 
> > --
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> 
> -- 
> Carlos
> --
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