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

[Mike Crowe <mac@mcrowe.com>]

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@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'
+    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] + '...'
+            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}:"
@@ -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"
-- 
2.20.1