[LU-18082] Support paths longer than PATH_MAX for fid2path

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0
• Affects Version/s: Lustre 2.16.0
• Labels: patch utils
• Severity: 3
• Assignee: Sebastien Buisson
• Reporter: Sebastien Buisson

Description

PATH_MAX affects the path length of a single pathname, but it is possible to exceed this by eg. creating a subdirectory tree, then cd into it (or use as a subdirectory mountpoint), then create a deep tree below this using a relative pathname.

So 'lfs fid2path' should not limit its output buffer to PATH_MAX.

Issue Links

• is related to: LU-14719 "lfs migrate -m" creates broken agent inodes when target MDT full

Comments

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/56369/
Subject: LU-18082 tests: fix sanity test_154i for interop
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 24366d89d610490fd94a0c6bb6aa44ca16dc9639

[Gerrit Updater]

"Sebastien Buisson <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/56369
Subject: LU-18082 tests: fix sanity test_154i for interop
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 05cfb3bec3ed3f79cfeb941abe0f344b9f490cfc

[Peter Jones]

Merged for 2.16

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/55897/
Subject: LU-18082 utils: fid2path support for path exceeding PATH_MAX
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: f5251cb7af4cfae8f2e9e7f69251253c0bc233b6

[Andreas Dilger]

I think there are more things to be fixed beyond just the userspace allocation. There was a patch in LU-14179 that fixed handling of long pathnames in "lfs find" (to at least PATH_MAX x 2).

I coincidentally also came across an old patch fragment that should be included in this patch, without which the fid2path code will spit console errors like:

[Wed Jul 31 15:04:10 2024] LustreError: 9096:0:(mdt_handler.c:7684:mdt_fid2path()) fid [0x200000404:0x3:0x0], path verylongpathnameforadeepdeepersubdir3/verylongpathnameforadeepdeepersubdir4/verylongpathnameforadeepdeepersubdir5/verylongpathnameforadeepdeepersubdir6/verylongpathnameforadeepdeepersubdir7/verylongpathnameforadeepdeepersubdir8/verylongpathnameforadeepdeepersubdir9/verylongpathnameforadeepdeepersubdir10/verylongpathnameforadeepdeepersubdir11/verylongpathnameforadeepdeepersubdir12/verylongpathnameforadeepdeepersubdir13/verylongpathnameforadeepdeepersubdir14/verylongpathnameforadeepdeepersubdir15/verylongpathnameforadeepdeepersubdir16/verylongpathnameforadeepdeepersubdir17/verylongpathnameforadeepdeepersubdir18/verylongpathnameforadeepdeepersubdir19/verylongpathnameforadeepdeepersubdir20/verylongpathnameforadeepdeepersubdir21/verylongpathnameforadeepdeepersubdir22/verylongpathnameforadeepdeepersubdir23/verylongpathnameforadeepdeepersubdir24/verylongpathnameforadeepdeepersubdir25/verylongpat
[Wed Jul 31 15:04:10 2024] LustreError: cowardly refusing to write 5308 bytes in a page

diff --git a/lustre/lmv/lmv_obd.c b/lustre/lmv/lmv_obd.c
index a8ee803473..f7af8e9e6e 100644
--- a/lustre/lmv/lmv_obd.c
+++ b/lustre/lmv/lmv_obd.c
@@ -601,10 +601,10 @@ repeat_fid2path:
                ptr[len] = '/';
        }
 
-       CDEBUG(D_INFO, "%s: get path %s "DFID" rec: %llu ln: %u\n",
+       CDEBUG(D_INFO, "%s: get path %.*s "DFID" rec: %llu ln: %u\n",
               tgt->ltd_exp->exp_obd->obd_name,
-              gf->gf_u.gf_path, PFID(&gf->gf_fid), gf->gf_recno,
-              gf->gf_linkno);
+              min(3072u, gf->gf_pathlen), gf->gf_u.gf_path, PFID(&gf->gf_fid),
+              gf->gf_recno, gf->gf_linkno);
 
        if (rc == 0)
                GOTO(out_fid2path, rc);
diff --git a/lustre/mdt/mdt_handler.c b/lustre/mdt/mdt_handler.c
index 65c956b819..3ca22e4509 100644
--- a/lustre/mdt/mdt_handler.c
+++ b/lustre/mdt/mdt_handler.c
@@ -6933,8 +6933,8 @@ static int mdt_fid2path(struct mdt_thread_info *info,
 
        rc = mdt_path(info, obj, fp, root_fid);
 
-       CDEBUG(D_INFO, "fid "DFID", path %s recno %#llx linkno %u\n",
-              PFID(&fp->gf_fid), fp->gf_u.gf_path,
+       CDEBUG(D_INFO, "fid "DFID", path %.*s recno %#llx linkno %u\n",
+              PFID(&fp->gf_fid), min(3072u, fp->gf_pathlen), fp->gf_u.gf_path,
               fp->gf_recno, fp->gf_linkno);
 
        mdt_object_put(info->mti_env, obj);

This has the effect of logging the first 3072 characters of the pathname, rather than the last 3072 characters. In this case (fid2path on multiple links) it might be better to log the last 3072 characters, like:

+       excess = fp->gf_pathlen > 3072 ? fp->gf_pathlen - 3072 : 0;
+       CDEBUG(D_INFO, "fid "DFID", path %.*s recno %#llx linkno %u\n",
+              PFID(&fp->gf_fid), fp->gf_pathlen - excess, fp->gf_u.gf_path + excess,
               fp->gf_recno, fp->gf_linkno);

[Gerrit Updater]

"Sebastien Buisson <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/55897
Subject: LU-18082 utils: fid2path support for path exceeding PATH_MAX
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 3e3d878791b66bf9c9844238beb8df269bc9332c