[bugfix] full file cache on XFS

src/overlaybd/cache/full_file_cache/cache_pool.cpp

@@ -232,6 +232,7 @@ void FileCachePool::eviction() {
         {
             photon::scoped_rwlock rl(lruEntry->rw_lock_, photon::WLOCK);
             err = mediaFs_->truncate(fileName.data(), 0);
+            lruEntry->truncate_done = false;
         }
 
         if (err) {

src/overlaybd/cache/full_file_cache/cache_pool.h

@@ -56,13 +56,14 @@ class FileCachePool : public FileSystem::ICachePool {
 
     struct LruEntry {
         LruEntry(uint32_t lruIt, int openCnt, uint64_t fileSize)
-            : lruIter(lruIt), openCount(openCnt), size(fileSize) {
+            : lruIter(lruIt), openCount(openCnt), size(fileSize), truncate_done(false) {
         }
         ~LruEntry() = default;
         uint32_t lruIter;
         int openCount;
         uint64_t size;
         photon::rwlock rw_lock_;
+        bool truncate_done;
     };
 
     // Normally, fileIndex(std::map) always keep growing, so its iterators always

src/overlaybd/cache/full_file_cache/cache_store.cpp

@@ -45,6 +45,13 @@ FileCacheStore::~FileCacheStore() {
     cachePool_->removeOpenFile(iterator_);
 }
 
+ICacheStore::try_preadv_result FileCacheStore::try_preadv2(const struct iovec *iov, int iovcnt,
+                                                           off_t offset, int flags) {
+    auto lruEntry = static_cast<FileCachePool::LruEntry *>(iterator_->second.get());
+    photon::scoped_rwlock rl(lruEntry->rw_lock_, photon::RLOCK);
+    return this->ICacheStore::try_preadv2(iov, iovcnt, offset, flags);
+}
+
 ssize_t FileCacheStore::do_preadv2(const struct iovec *iov, int iovcnt, off_t offset, int flags) {
     // TODO(suoshi.yf): maybe a new interface for updating lru is better for avoiding
     // multiple cacheStore preadvs but cacheFile preadv only once
@@ -60,6 +67,16 @@ ssize_t FileCacheStore::do_preadv2(const struct iovec *iov, int iovcnt, off_t of
 ssize_t FileCacheStore::do_pwritev(const struct iovec *iov, int iovcnt, off_t offset) {
     ssize_t ret;
     iovector_view view((iovec *)iov, iovcnt);
+    auto lruEntry = static_cast<FileCachePool::LruEntry *>(iterator_->second.get());
+    photon::scoped_rwlock rl(lruEntry->rw_lock_, photon::RLOCK);
+    if (!lruEntry->truncate_done) {
+        // May repeated ftruncate() here, but it doesn't matter
+        ret = localFile_->ftruncate(actual_size_);
+        if (ret) {
+            LOG_ERRNO_RETURN(0, -1, "failed to truncate media file: ", VALUE(ret));
+        }
+        lruEntry->truncate_done = true;
+    }
     ScopedRangeLock lock(rangeLock_, offset, view.sum());
     SCOPE_AUDIT_THRESHOLD(10UL * 1000, "file:write", AU_FILEOP("", offset, ret));
     ret = localFile_->pwritev(iov, iovcnt, offset);

src/overlaybd/cache/full_file_cache/cache_store.h

@@ -31,6 +31,8 @@ class FileCacheStore : public FileSystem::ICacheStore {
                    size_t refillUnit, FileIterator iterator);
     ~FileCacheStore();
 
+    try_preadv_result try_preadv2(const struct iovec *iov, int iovcnt, off_t offset, int flags) override;
+
     ssize_t do_preadv2(const struct iovec *iov, int iovcnt, off_t offset, int flags) override;
 
     ssize_t do_pwritev2(const struct iovec *iov, int iovcnt, off_t offset, int flags) override;