01/07: daemon: Correctly handle EMLINK corner case when deduplicating.

[guix-commits]

civodul pushed a commit to branch master
in repository guix.

commit b930f0ba2115f71c323d4bf3d72efb763f716296
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Thu Jun 25 10:07:09 2020 +0200

    daemon: Correctly handle EMLINK corner case when deduplicating.
    
    Suggested by Caleb Ristvedt <caleb.ristvedt@cune.org>.
    
    * nix/libstore/optimise-store.cc (LocalStore::optimisePath_): Save errno
    from 'rename' before calling 'unlink'.
---
 nix/libstore/optimise-store.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/nix/libstore/optimise-store.cc b/nix/libstore/optimise-store.cc
index d8f8d23..eb303ab 100644
--- a/nix/libstore/optimise-store.cc
+++ b/nix/libstore/optimise-store.cc
@@ -215,9 +215,10 @@ void LocalStore::optimisePath_(OptimiseStats & stats, 
const Path & path, InodeHa
 
     /* Atomically replace the old file with the new hard link. */
     if (rename(tempLink.c_str(), path.c_str()) == -1) {
+       int renameErrno = errno;
         if (unlink(tempLink.c_str()) == -1)
             printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
-        if (errno == EMLINK) {
+        if (renameErrno == EMLINK) {
             /* Some filesystems generate too many links on the rename,
                rather than on the original link.  (Probably it
                temporarily increases the st_nlink field before