[OE-core] [PATCH] sstate: Truncate PV in sstate filenames that are too long

[Mark Hatle]

On 7/30/19 6:01 AM, Mike Crowe wrote:
> sstate filenames are generated by concatenating a variety of bits of
> package metadata. Some of these parts could be long, which could cause
> the filename to be longer than the 255 character maximum for ext4.
> 
> So, let's try to detect this situation and truncate the PV part of the
> filename so that it will fit. If this happens, an ellipsis is added to
> make it clear that the version number is incomplete.
> 
> SSTATE_PKG needs to be consistent for all tasks so that the hash
> remains stable. This means that we need to make an assumption for the
> maximum length of the task name. In this implementation, the task name
> is limited to 27 characters.
> 
> This change also results in a sensible error message being emitted if
> the resulting filename is still too long.
> 
> Signed-off-by: Mike Crowe <mac at mcrowe.com>
> 
> diff --git a/meta/classes/sstate.bbclass b/meta/classes/sstate.bbclass
> index 3342c5ef50..6313b1c538 100644
> --- a/meta/classes/sstate.bbclass
> +++ b/meta/classes/sstate.bbclass
> @@ -8,6 +8,24 @@ def generate_sstatefn(spec, hash, d):
>          hash = "INVALID"
>      return hash[:2] + "/" + spec + hash
>  
> +def sstate_path(taskname, d):
> +    max_filename_len = 245 # leave some room for ".siginfo"
> +    max_addendum_len = 32 # '_' + taskname + '.tgz'

Since the task name is variable, is there really a 32 character limit here?

It may make sense to do:

# '_' + taskname + '.tgz', reserving a minimum of 32 for taskname
max_addendum_len = len(taskname) + 5 if len(taskname) + 5 > 32 else 32

Always reserve a minimum of 32 for consistency, but if we go over account for it.

> +    sstate_prefix = d.getVar('SSTATE_PKG')
> +    excess = len(os.path.basename(sstate_prefix)) - (max_filename_len - max_addendum_len)
> +    if excess > 0:
> +        pv = d.getVar('PV')
> +        if len(pv) >= excess and len(pv) >= 3:
> +            short_pv = d.getVar('PV')[:-excess-3] + '...'

Is truncating the PV enough?  In a discussion on the bitbake list, I suggested
possibly changing the order of the entries in the SSTATE_PKGSPEC to allow us to
prune things prior to the hash w/o affecting the hash.  Maybe this is simply not
needed.. but it's a possibility if this proves to not be effective.

> +            d2 = d.createCopy()
> +            d2.setVar('PV', short_pv)
> +            sstate_prefix = d2.getVar('SSTATE_PKG')
> +
> +    sstatepkg = sstate_prefix + '_'+ taskname + ".tgz"
> +    if len(os.path.basename(sstatepkg)) > max_filename_len:
> +        bb.error('Failed to shorten sstate filename')
> +    return sstatepkg
> +
>  SSTATE_PKGARCH    = "${PACKAGE_ARCH}"
>  SSTATE_PKGSPEC    = "sstate:${PN}:${PACKAGE_ARCH}${TARGET_VENDOR}-${TARGET_OS}:${PV}:${PR}:${SSTATE_PKGARCH}:${SSTATE_VERSION}:"
>  SSTATE_SWSPEC     = "sstate:${PN}::${PV}:${PR}::${SSTATE_VERSION}:"

There is something else I noticed..  "SSTATE_PKGNAME" defined as:

SSTATE_PKGNAME    =
"${SSTATE_EXTRAPATH}${@generate_sstatefn(d.getVar('SSTATE_PKGSPEC'),
d.getVar('BB_UNIHASH'), d)}"

>From what I can tell, this really should be using the new sstate_path function
in someway.

Would it make more sense to define SSTATE_PKGNAME in such a way that it always
resulted in something "short" enough, and in the right format, that it would
always work?

Adjusting or rewriting "generate_sstatefn" could still accomplish the PV change,
but the max length of the string would need further shrinking to accommodate an
unknown task length (which goes back to my previous comment).  If the 32 default
is long enough then that shouldn't be a problem -- and may also resolve my
concerns that something outside of sstate class could try to use that various
and without the new magic function get the wrong results.

Anyway, my immediate 2 cents...

--Mark

> @@ -323,7 +341,7 @@ def sstate_installpkg(ss, d):
>  
>      sstateinst = d.expand("${WORKDIR}/sstate-install-%s/" % ss['task'])
>      sstatefetch = d.getVar('SSTATE_PKGNAME') + '_' + ss['task'] + ".tgz"
> -    sstatepkg = d.getVar('SSTATE_PKG') + '_' + ss['task'] + ".tgz"
> +    sstatepkg = sstate_path(ss['task'], d)
>  
>      if not os.path.exists(sstatepkg):
>          pstaging_fetch(sstatefetch, d)
> @@ -617,7 +635,7 @@ def sstate_package(ss, d):
>      tmpdir = d.getVar('TMPDIR')
>  
>      sstatebuild = d.expand("${WORKDIR}/sstate-build-%s/" % ss['task'])
> -    sstatepkg = d.getVar('SSTATE_PKG') + '_'+ ss['task'] + ".tgz"
> +    sstatepkg = sstate_path(ss['task'], d)
>      bb.utils.remove(sstatebuild, recurse=True)
>      bb.utils.mkdirhier(sstatebuild)
>      bb.utils.mkdirhier(os.path.dirname(sstatepkg))
> @@ -1084,8 +1102,8 @@ python sstate_eventhandler() {
>          if taskname in ["fetch", "unpack", "patch", "populate_lic", "preconfigure"] and swspec:
>              d.setVar("SSTATE_PKGSPEC", "${SSTATE_SWSPEC}")
>              d.setVar("SSTATE_EXTRAPATH", "")
> -        sstatepkg = d.getVar('SSTATE_PKG')
> -        bb.siggen.dump_this_task(sstatepkg + '_' + taskname + ".tgz" ".siginfo", d)
> +        sstateinfo = sstate_path(taskname, d) + ".siginfo"
> +        bb.siggen.dump_this_task(sstateinfo, d)
>  }
>  
>  SSTATE_PRUNE_OBSOLETEWORKDIR ?= "1"
>