[Nix-dev] [PATCH] Handle "too many links" from btrfs.

[David Brown]

The btrfs seems to report "too many links" when attempting to rename
the temp link.  Handle this case in the same manner as generating too
many links.
---
 src/libstore/optimise-store.cc |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/src/libstore/optimise-store.cc b/src/libstore/optimise-store.cc
index d150492..9a3b354 100644
--- a/src/libstore/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -119,9 +119,21 @@ static void hashAndLink(bool dryRun, HashToPath & hashToPath,
             }
 
             /* Atomically replace the old file with the new hard link. */
-            if (rename(tempLink.c_str(), path.c_str()) == -1)
+            if (rename(tempLink.c_str(), path.c_str()) == -1) {
+                if (errno == EMLINK) {
+                    /* Some filesystems generate too many links on the
+                     * rename, rather than on the original link. */
+                    printMsg(lvlInfo, format("`%1%' has maximum number of links") % prevPath.first);
+                    hashToPath[hash] = std::pair<Path, ino_t>(path, st.st_ino);
+
+                    /* Unlink the temp link. */
+                    if (unlink(tempLink.c_str()) == -1)
+                        printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
+                    return;
+                }
                 throw SysError(format("cannot rename `%1%' to `%2%'")
                     % tempLink % path);
+            }
         } else
             printMsg(lvlTalkative, format("would link `%1%' to `%2%'") % path % prevPath.first);
         
-- 
1.7.1