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36457566 LC |
1 | #include "config.h" |
2 | ||
3 | #include "util.hh" | |
4 | #include "local-store.hh" | |
5 | #include "globals.hh" | |
6 | ||
54c260e6 | 7 | #include <cstdlib> |
36457566 LC |
8 | #include <sys/types.h> |
9 | #include <sys/stat.h> | |
10 | #include <unistd.h> | |
11 | #include <errno.h> | |
12 | #include <stdio.h> | |
13 | ||
14 | ||
15 | namespace nix { | |
16 | ||
17 | ||
18 | static void makeWritable(const Path & path) | |
19 | { | |
20 | struct stat st; | |
21 | if (lstat(path.c_str(), &st)) | |
22 | throw SysError(format("getting attributes of path `%1%'") % path); | |
23 | if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1) | |
24 | throw SysError(format("changing writability of `%1%'") % path); | |
25 | } | |
26 | ||
27 | ||
28 | struct MakeReadOnly | |
29 | { | |
30 | Path path; | |
31 | MakeReadOnly(const Path & path) : path(path) { } | |
32 | ~MakeReadOnly() | |
33 | { | |
34 | try { | |
35 | /* This will make the path read-only. */ | |
36 | if (path != "") canonicaliseTimestampAndPermissions(path); | |
37 | } catch (...) { | |
38 | ignoreException(); | |
39 | } | |
40 | } | |
41 | }; | |
42 | ||
43 | ||
15ddeff5 LC |
44 | LocalStore::InodeHash LocalStore::loadInodeHash() |
45 | { | |
46 | printMsg(lvlDebug, "loading hash inodes in memory"); | |
47 | InodeHash inodeHash; | |
48 | ||
49 | AutoCloseDir dir = opendir(linksDir.c_str()); | |
50 | if (!dir) throw SysError(format("opening directory `%1%'") % linksDir); | |
51 | ||
52 | struct dirent * dirent; | |
53 | while (errno = 0, dirent = readdir(dir)) { /* sic */ | |
54 | checkInterrupt(); | |
55 | // We don't care if we hit non-hash files, anything goes | |
56 | inodeHash.insert(dirent->d_ino); | |
57 | } | |
58 | if (errno) throw SysError(format("reading directory `%1%'") % linksDir); | |
59 | ||
60 | printMsg(lvlTalkative, format("loaded %1% hash inodes") % inodeHash.size()); | |
61 | ||
62 | return inodeHash; | |
63 | } | |
64 | ||
65 | ||
66 | Strings LocalStore::readDirectoryIgnoringInodes(const Path & path, const InodeHash & inodeHash) | |
67 | { | |
68 | Strings names; | |
69 | ||
70 | AutoCloseDir dir = opendir(path.c_str()); | |
71 | if (!dir) throw SysError(format("opening directory `%1%'") % path); | |
72 | ||
73 | struct dirent * dirent; | |
74 | while (errno = 0, dirent = readdir(dir)) { /* sic */ | |
75 | checkInterrupt(); | |
76 | ||
77 | if (inodeHash.count(dirent->d_ino)) { | |
78 | printMsg(lvlDebug, format("`%1%' is already linked") % dirent->d_name); | |
79 | continue; | |
80 | } | |
81 | ||
82 | string name = dirent->d_name; | |
83 | if (name == "." || name == "..") continue; | |
84 | names.push_back(name); | |
85 | } | |
86 | if (errno) throw SysError(format("reading directory `%1%'") % path); | |
87 | ||
88 | return names; | |
89 | } | |
90 | ||
91 | ||
92 | void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path, InodeHash & inodeHash) | |
36457566 LC |
93 | { |
94 | checkInterrupt(); | |
15ddeff5 | 95 | |
36457566 LC |
96 | struct stat st; |
97 | if (lstat(path.c_str(), &st)) | |
98 | throw SysError(format("getting attributes of path `%1%'") % path); | |
99 | ||
100 | if (S_ISDIR(st.st_mode)) { | |
15ddeff5 | 101 | Strings names = readDirectoryIgnoringInodes(path, inodeHash); |
36457566 | 102 | foreach (Strings::iterator, i, names) |
15ddeff5 | 103 | optimisePath_(stats, path + "/" + *i, inodeHash); |
36457566 LC |
104 | return; |
105 | } | |
106 | ||
107 | /* We can hard link regular files and maybe symlinks. */ | |
108 | if (!S_ISREG(st.st_mode) | |
109 | #if CAN_LINK_SYMLINK | |
110 | && !S_ISLNK(st.st_mode) | |
111 | #endif | |
112 | ) return; | |
113 | ||
114 | /* Sometimes SNAFUs can cause files in the Nix store to be | |
115 | modified, in particular when running programs as root under | |
116 | NixOS (example: $fontconfig/var/cache being modified). Skip | |
117 | those files. FIXME: check the modification time. */ | |
118 | if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) { | |
119 | printMsg(lvlError, format("skipping suspicious writable file `%1%'") % path); | |
120 | return; | |
121 | } | |
122 | ||
e134baae | 123 | /* This can still happen on top-level files. */ |
15ddeff5 LC |
124 | if (st.st_nlink > 1 && inodeHash.count(st.st_ino)) { |
125 | printMsg(lvlDebug, format("`%1%' is already linked, with %2% other file(s).") % path % (st.st_nlink - 2)); | |
126 | return; | |
127 | } | |
128 | ||
36457566 LC |
129 | /* Hash the file. Note that hashPath() returns the hash over the |
130 | NAR serialisation, which includes the execute bit on the file. | |
131 | Thus, executable and non-executable files with the same | |
132 | contents *won't* be linked (which is good because otherwise the | |
133 | permissions would be screwed up). | |
134 | ||
135 | Also note that if `path' is a symlink, then we're hashing the | |
136 | contents of the symlink (i.e. the result of readlink()), not | |
137 | the contents of the target (which may not even exist). */ | |
138 | Hash hash = hashPath(htSHA256, path).first; | |
36457566 LC |
139 | printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash)); |
140 | ||
141 | /* Check if this is a known hash. */ | |
142 | Path linkPath = linksDir + "/" + printHash32(hash); | |
143 | ||
e134baae | 144 | retry: |
36457566 LC |
145 | if (!pathExists(linkPath)) { |
146 | /* Nope, create a hard link in the links directory. */ | |
15ddeff5 LC |
147 | if (link(path.c_str(), linkPath.c_str()) == 0) { |
148 | inodeHash.insert(st.st_ino); | |
149 | return; | |
150 | } | |
36457566 LC |
151 | if (errno != EEXIST) |
152 | throw SysError(format("cannot link `%1%' to `%2%'") % linkPath % path); | |
153 | /* Fall through if another process created ‘linkPath’ before | |
154 | we did. */ | |
155 | } | |
156 | ||
157 | /* Yes! We've seen a file with the same contents. Replace the | |
158 | current file with a hard link to that file. */ | |
159 | struct stat stLink; | |
160 | if (lstat(linkPath.c_str(), &stLink)) | |
161 | throw SysError(format("getting attributes of path `%1%'") % linkPath); | |
162 | ||
36457566 LC |
163 | if (st.st_ino == stLink.st_ino) { |
164 | printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % linkPath); | |
165 | return; | |
166 | } | |
167 | ||
e134baae ED |
168 | if (st.st_size != stLink.st_size) { |
169 | printMsg(lvlError, format("removing corrupted link ‘%1%’") % linkPath); | |
170 | unlink(linkPath.c_str()); | |
171 | goto retry; | |
172 | } | |
173 | ||
174 | printMsg(lvlTalkative, format("linking ‘%1%’ to ‘%2%’") % path % linkPath); | |
36457566 LC |
175 | |
176 | /* Make the containing directory writable, but only if it's not | |
177 | the store itself (we don't want or need to mess with its | |
178 | permissions). */ | |
179 | bool mustToggle = !isStorePath(path); | |
180 | if (mustToggle) makeWritable(dirOf(path)); | |
181 | ||
182 | /* When we're done, make the directory read-only again and reset | |
183 | its timestamp back to 0. */ | |
184 | MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : ""); | |
185 | ||
186 | Path tempLink = (format("%1%/.tmp-link-%2%-%3%") | |
187 | % settings.nixStore % getpid() % rand()).str(); | |
188 | ||
189 | if (link(linkPath.c_str(), tempLink.c_str()) == -1) { | |
190 | if (errno == EMLINK) { | |
191 | /* Too many links to the same file (>= 32000 on most file | |
192 | systems). This is likely to happen with empty files. | |
193 | Just shrug and ignore. */ | |
194 | if (st.st_size) | |
195 | printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath); | |
196 | return; | |
197 | } | |
198 | throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % linkPath); | |
199 | } | |
200 | ||
201 | /* Atomically replace the old file with the new hard link. */ | |
202 | if (rename(tempLink.c_str(), path.c_str()) == -1) { | |
203 | if (unlink(tempLink.c_str()) == -1) | |
204 | printMsg(lvlError, format("unable to unlink `%1%'") % tempLink); | |
205 | if (errno == EMLINK) { | |
206 | /* Some filesystems generate too many links on the rename, | |
207 | rather than on the original link. (Probably it | |
208 | temporarily increases the st_nlink field before | |
209 | decreasing it again.) */ | |
210 | if (st.st_size) | |
211 | printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath); | |
212 | return; | |
213 | } | |
214 | throw SysError(format("cannot rename `%1%' to `%2%'") % tempLink % path); | |
215 | } | |
216 | ||
217 | stats.filesLinked++; | |
218 | stats.bytesFreed += st.st_size; | |
219 | stats.blocksFreed += st.st_blocks; | |
220 | } | |
221 | ||
222 | ||
223 | void LocalStore::optimiseStore(OptimiseStats & stats) | |
224 | { | |
225 | PathSet paths = queryAllValidPaths(); | |
15ddeff5 | 226 | InodeHash inodeHash = loadInodeHash(); |
36457566 LC |
227 | |
228 | foreach (PathSet::iterator, i, paths) { | |
229 | addTempRoot(*i); | |
230 | if (!isValidPath(*i)) continue; /* path was GC'ed, probably */ | |
231 | startNest(nest, lvlChatty, format("hashing files in `%1%'") % *i); | |
15ddeff5 | 232 | optimisePath_(stats, *i, inodeHash); |
36457566 LC |
233 | } |
234 | } | |
235 | ||
2bb04905 LC |
236 | static string showBytes(unsigned long long bytes) |
237 | { | |
238 | return (format("%.2f MiB") % (bytes / (1024.0 * 1024.0))).str(); | |
239 | } | |
240 | ||
241 | void LocalStore::optimiseStore() | |
242 | { | |
243 | OptimiseStats stats; | |
244 | ||
245 | optimiseStore(stats); | |
246 | ||
247 | printMsg(lvlError, | |
248 | format("%1% freed by hard-linking %2% files") | |
249 | % showBytes(stats.bytesFreed) | |
250 | % stats.filesLinked); | |
251 | } | |
36457566 LC |
252 | |
253 | void LocalStore::optimisePath(const Path & path) | |
254 | { | |
255 | OptimiseStats stats; | |
15ddeff5 LC |
256 | InodeHash inodeHash; |
257 | ||
258 | if (settings.autoOptimiseStore) optimisePath_(stats, path, inodeHash); | |
36457566 LC |
259 | } |
260 | ||
261 | ||
262 | } |