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#include "config.h"
#include "util.hh"
#include "local-store.hh"
#include "globals.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
namespace nix {
static void makeWritable(const Path & path)
{
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
throw SysError(format("changing writability of `%1%'") % path);
}
struct MakeReadOnly
{
Path path;
MakeReadOnly(const Path & path) : path(path) { }
~MakeReadOnly()
{
try {
/* This will make the path read-only. */
if (path != "") canonicaliseTimestampAndPermissions(path);
} catch (...) {
ignoreException();
}
}
};
void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path)
{
checkInterrupt();
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
if (S_ISDIR(st.st_mode)) {
Strings names = readDirectory(path);
foreach (Strings::iterator, i, names)
optimisePath_(stats, path + "/" + *i);
return;
}
/* We can hard link regular files and maybe symlinks. */
if (!S_ISREG(st.st_mode)
#if CAN_LINK_SYMLINK
&& !S_ISLNK(st.st_mode)
#endif
) return;
/* Sometimes SNAFUs can cause files in the Nix store to be
modified, in particular when running programs as root under
NixOS (example: $fontconfig/var/cache being modified). Skip
those files. FIXME: check the modification time. */
if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) {
printMsg(lvlError, format("skipping suspicious writable file `%1%'") % path);
return;
}
/* Hash the file. Note that hashPath() returns the hash over the
NAR serialisation, which includes the execute bit on the file.
Thus, executable and non-executable files with the same
contents *won't* be linked (which is good because otherwise the
permissions would be screwed up).
Also note that if `path' is a symlink, then we're hashing the
contents of the symlink (i.e. the result of readlink()), not
the contents of the target (which may not even exist). */
Hash hash = hashPath(htSHA256, path).first;
stats.totalFiles++;
printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash));
/* Check if this is a known hash. */
Path linkPath = linksDir + "/" + printHash32(hash);
if (!pathExists(linkPath)) {
/* Nope, create a hard link in the links directory. */
if (link(path.c_str(), linkPath.c_str()) == 0) return;
if (errno != EEXIST)
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
current file with a hard link to that file. */
struct stat stLink;
if (lstat(linkPath.c_str(), &stLink))
throw SysError(format("getting attributes of path `%1%'") % linkPath);
stats.sameContents++;
if (st.st_ino == stLink.st_ino) {
printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % linkPath);
return;
}
printMsg(lvlTalkative, format("linking `%1%' to `%2%'") % path % linkPath);
/* Make the containing directory writable, but only if it's not
the store itself (we don't want or need to mess with its
permissions). */
bool mustToggle = !isStorePath(path);
if (mustToggle) makeWritable(dirOf(path));
/* When we're done, make the directory read-only again and reset
its timestamp back to 0. */
MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : "");
Path tempLink = (format("%1%/.tmp-link-%2%-%3%")
% settings.nixStore % getpid() % rand()).str();
if (link(linkPath.c_str(), tempLink.c_str()) == -1) {
if (errno == EMLINK) {
/* Too many links to the same file (>= 32000 on most file
systems). This is likely to happen with empty files.
Just shrug and ignore. */
if (st.st_size)
printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
return;
}
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) {
if (unlink(tempLink.c_str()) == -1)
printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
if (errno == 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
decreasing it again.) */
if (st.st_size)
printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
return;
}
throw SysError(format("cannot rename `%1%' to `%2%'") % tempLink % path);
}
stats.filesLinked++;
stats.bytesFreed += st.st_size;
stats.blocksFreed += st.st_blocks;
}
void LocalStore::optimiseStore(OptimiseStats & stats)
{
PathSet paths = queryAllValidPaths();
foreach (PathSet::iterator, i, paths) {
addTempRoot(*i);
if (!isValidPath(*i)) continue; /* path was GC'ed, probably */
startNest(nest, lvlChatty, format("hashing files in `%1%'") % *i);
optimisePath_(stats, *i);
}
}
void LocalStore::optimisePath(const Path & path)
{
OptimiseStats stats;
if (settings.autoOptimiseStore) optimisePath_(stats, path);
}
}
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