04/05: daemon: Do not error out when deduplication fails due to ENOSPC.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit 12b6c951cf5ca6055a22a2eec85665353f5510e5
Author: Ludovic Courtès <address@hidden>
Date:   Fri Oct 28 20:34:15 2016 +0200

    daemon: Do not error out when deduplication fails due to ENOSPC.
    
    This solves a problem whereby if /gnu/store/.links had enough entries,
    ext4's directory index would be full, leading to link(2) returning
    ENOSPC.
    
    * nix/libstore/optimise-store.cc (LocalStore::optimisePath_): Upon
    ENOSPC from link(2), print a message and return instead of throwing a
    'SysError'.
---
 nix/libstore/optimise-store.cc |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/nix/libstore/optimise-store.cc b/nix/libstore/optimise-store.cc
index d7508b0..565c62c 100644
--- a/nix/libstore/optimise-store.cc
+++ b/nix/libstore/optimise-store.cc
@@ -148,10 +148,23 @@ void LocalStore::optimisePath_(OptimiseStats & stats, 
const Path & path, InodeHa
             inodeHash.insert(st.st_ino);
             return;
         }
-        if (errno != EEXIST)
+
+       switch (errno) {
+       case EEXIST:
+           /* Fall through if another process created ‘linkPath’ before
+              we did. */
+           break;
+
+       case ENOSPC:
+           /* On ext4, that probably means the directory index is full.  When
+              that happens, it's fine to ignore it: we just effectively
+              disable deduplication of this file.  */
+           printMsg(lvlInfo, format("cannot link `%1%' to `%2%': %m") % 
linkPath % path);
+           return;
+
+       default:
             throw SysError(format("cannot link `%1%' to `%2%'") % linkPath % 
path);
-        /* Fall through if another process created ‘linkPath’ before
-           we did. */
+       }
     }
 
     /* Yes!  We've seen a file with the same contents.  Replace the
@@ -195,8 +208,8 @@ void LocalStore::optimisePath_(OptimiseStats & stats, const 
Path & path, InodeHa
                 printMsg(lvlInfo, format("`%1%' has maximum number of links") 
% linkPath);
             return;
         }
-        throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % 
linkPath);
-    }
+           throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % 
linkPath);
+       }
 
     /* Atomically replace the old file with the new hard link. */
     if (rename(tempLink.c_str(), path.c_str()) == -1) {