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optimise: reduce lstat and use correct inode #15831

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33 changes: 19 additions & 14 deletions src/libstore/optimise-store.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -163,34 +163,40 @@ void LocalStore::optimisePath_(
/* Check if this is a known hash. */
std::filesystem::path linkPath = std::filesystem::path{linksDir} / hash.to_string(HashFormat::Nix32, false);

/* Stat the link once, if it exists. */
auto stLink = maybeLstat(linkPath);

/* Maybe delete the link, if it has been corrupted. */
if (pathExists(linkPath)) {
auto stLink = lstat(linkPath);
if (st.st_size != stLink.st_size || (repair && hash != ({
hashPath(
makeFSSourceAccessor(linkPath),
FileSerialisationMethod::NixArchive,
HashAlgorithm::SHA256)
.hash;
}))) {
if (stLink) {
if (st.st_size != stLink->st_size || (repair && hash != ({
hashPath(
makeFSSourceAccessor(linkPath),
FileSerialisationMethod::NixArchive,
HashAlgorithm::SHA256)
.hash;
}))) {
// XXX: Consider overwriting linkPath with our valid version.
warn("removing corrupted link %s", PathFmt(linkPath));
warn(
"There may be more corrupted paths."
"\nYou should run `nix-store --verify --check-contents --repair` to fix them all");
unlinkIfExists(linkPath);
stLink.reset();
}
}

if (!pathExists(linkPath)) {
if (!stLink) {
/* Nope, create a hard link in the links directory. */
try {
std::filesystem::create_hard_link(path, linkPath);
inodeHash.insert(st.st_ino);
stLink = lstat(linkPath);
inodeHash.insert(stLink->st_ino);
} catch (std::filesystem::filesystem_error & e) {
if (e.code() == std::errc::file_exists) {
/* Fall through if another process created ‘linkPath’ before
we did. */
stLink = lstat(linkPath);
inodeHash.insert(stLink->st_ino);
}

else if (e.code() == std::errc::no_space_on_device) {
Expand All @@ -210,9 +216,8 @@ void LocalStore::optimisePath_(

/* Yes! We've seen a file with the same contents. Replace the
current file with a hard link to that file. */
auto stLink = lstat(linkPath);

if (st.st_ino == stLink.st_ino) {
if (st.st_ino == stLink->st_ino) {
debug("%1% is already linked to %2%", PathFmt(path), PathFmt(linkPath));
return;
}
Expand All @@ -235,7 +240,7 @@ void LocalStore::optimisePath_(

try {
std::filesystem::create_hard_link(linkPath, tempLink);
inodeHash.insert(st.st_ino);
inodeHash.insert(stLink->st_ino);
} catch (std::filesystem::filesystem_error & e) {
if (e.code() == std::errc::too_many_links) {
/* Too many links to the same file (>= 32000 on most file
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