Support falling back to buffered I/O when direct I/O is unavailable (#6174)

4 files changed, 47 insertions, 36 deletions

diff --git a/database/engine/datafile.c b/database/engine/datafile.c
index 2d17d05e42..9262805c81 100644
--- a/database/engine/datafile.c
+++ b/database/engine/datafile.c
@@ -100,18 +100,10 @@ int create_data_file(struct rrdengine_datafile *datafile)
     char path[1024];
 
     generate_datafilepath(datafile, path, sizeof(path));
-    fd = uv_fs_open(NULL, &req, path, O_DIRECT | O_CREAT | O_RDWR | O_TRUNC,
-                    S_IRUSR | S_IWUSR, NULL);
+    fd = open_file_direct_io(path, O_CREAT | O_RDWR | O_TRUNC, &file);
     if (fd < 0) {
         fatal("uv_fs_fsopen: %s", uv_strerror(fd));
     }
-    assert(req.result >= 0);
-    file = req.result;
-    uv_fs_req_cleanup(&req);
-#ifdef __APPLE__
-    info("Disabling OS X caching for file \"%s\".", path);
-    fcntl(fd, F_NOCACHE, 1);
-#endif
 
     ret = posix_memalign((void *)&superblock, RRDFILE_ALIGNMENT, sizeof(*superblock));
     if (unlikely(ret)) {
@@ -187,20 +179,12 @@ static int load_data_file(struct rrdengine_datafile *datafile)
     char path[1024];
 
     generate_datafilepath(datafile, path, sizeof(path));
-    fd = uv_fs_open(NULL, &req, path, O_DIRECT | O_RDWR, S_IRUSR | S_IWUSR, NULL);
+    fd = open_file_direct_io(path, O_RDWR, &file);
     if (fd < 0) {
         /* if (UV_ENOENT != fd) */
         error("uv_fs_fsopen: %s", uv_strerror(fd));
-        uv_fs_req_cleanup(&req);
         return fd;
     }
-    assert(req.result >= 0);
-    file = req.result;
-    uv_fs_req_cleanup(&req);
-#ifdef __APPLE__
-    info("Disabling OS X caching for file \"%s\".", path);
-    fcntl(fd, F_NOCACHE, 1);
-#endif
     info("Initializing data file \"%s\".", path);
 
     ret = check_file_properties(file, &file_size, sizeof(struct rrdeng_df_sb));
diff --git a/database/engine/journalfile.c b/database/engine/journalfile.c
index e85b09cfda..9b14c914df 100644
--- a/database/engine/journalfile.c
+++ b/database/engine/journalfile.c
@@ -146,18 +146,10 @@ int create_journal_file(struct rrdengine_journalfile *journalfile, struct rrdeng
     char path[1024];
 
     generate_journalfilepath(datafile, path, sizeof(path));
-    fd = uv_fs_open(NULL, &req, path, O_DIRECT | O_CREAT | O_RDWR | O_TRUNC,
-                    S_IRUSR | S_IWUSR, NULL);
+    fd = open_file_direct_io(path, O_CREAT | O_RDWR | O_TRUNC, &file);
     if (fd < 0) {
         fatal("uv_fs_fsopen: %s", uv_strerror(fd));
     }
-    assert(req.result >= 0);
-    file = req.result;
-    uv_fs_req_cleanup(&req);
-#ifdef __APPLE__
-    info("Disabling OS X caching for file \"%s\".", path);
-    fcntl(fd, F_NOCACHE, 1);
-#endif
 
     ret = posix_memalign((void *)&superblock, RRDFILE_ALIGNMENT, sizeof(*superblock));
     if (unlikely(ret)) {
@@ -411,20 +403,12 @@ int load_journal_file(struct rrdengine_instance *ctx, struct rrdengine_journalfi
     char path[1024];
 
     generate_journalfilepath(datafile, path, sizeof(path));
-    fd = uv_fs_open(NULL, &req, path, O_DIRECT | O_RDWR, S_IRUSR | S_IWUSR, NULL);
+    fd = open_file_direct_io(path, O_RDWR, &file);
     if (fd < 0) {
         /* if (UV_ENOENT != fd) */
         error("uv_fs_fsopen: %s", uv_strerror(fd));
-        uv_fs_req_cleanup(&req);
         return fd;
     }
-    assert(req.result >= 0);
-    file = req.result;
-    uv_fs_req_cleanup(&req);
-#ifdef __APPLE__
-    info("Disabling OS X caching for file \"%s\".", path);
-    fcntl(fd, F_NOCACHE, 1);
-#endif
     info("Loading journal file \"%s\".", path);
 
     ret = check_file_properties(file, &file_size, sizeof(struct rrdeng_df_sb));
diff --git a/database/engine/rrdenginelib.c b/database/engine/rrdenginelib.c
index 176a01dcc1..0523d54e7e 100644
--- a/database/engine/rrdenginelib.c
+++ b/database/engine/rrdenginelib.c
@@ -78,6 +78,48 @@ int check_file_properties(uv_file file, uint64_t *file_size, size_t min_size)
     return 0;
 }
 
+/*
+ * Tries to open a file in direct I/O mode, falls back to buffered mode if not possible.
+ * Returns UV error number that is < 0 on failure.
+ * On success sets (*file) to be the uv_file that was opened.
+ */
+int open_file_direct_io(char *path, int flags, uv_file *file)
+{
+    uv_fs_t req;
+    int fd, current_flags, direct;
+
+    for (direct = 1 ; direct >= 0 ; --direct) {
+#ifdef __APPLE__
+        /* Apple OS does not support O_DIRECT */
+        direct = 0;
+#endif
+        current_flags = flags;
+        if (direct) {
+            current_flags |= O_DIRECT;
+        }
+        fd = uv_fs_open(NULL, &req, path, current_flags, S_IRUSR | S_IWUSR, NULL);
+        if (fd < 0) {
+            if ((direct) && (UV_EINVAL == fd)) {
+                error("File \"%s\" does not support direct I/O, falling back to buffered I/O.", path);
+            } else {
+                error("Failed to open file \"%s\".", path);
+                return fd;
+            }
+        } else {
+            assert(req.result >= 0);
+            *file = req.result;
+#ifdef __APPLE__
+            info("Disabling OS X caching for file \"%s\".", path);
+            fcntl(fd, F_NOCACHE, 1);
+#endif
+            --direct; /* break the loop */
+        }
+        uv_fs_req_cleanup(&req);
+    }
+
+    return fd;
+}
+
 char *get_rrdeng_statistics(struct rrdengine_instance *ctx, char *str, size_t size)
 {
     struct page_cache *pg_cache;
diff --git a/database/engine/rrdenginelib.h b/database/engine/rrdenginelib.h
index 5873e47234..c71cdd1220 100644
--- a/database/engine/rrdenginelib.h
+++ b/database/engine/rrdenginelib.h
@@ -93,6 +93,7 @@ static inline void crc32set(void *crcp, uLong crc)
 extern void print_page_cache_descr(struct rrdeng_page_descr *page_cache_descr);
 extern void print_page_descr(struct rrdeng_page_descr *descr);
 extern int check_file_properties(uv_file file, uint64_t *file_size, size_t min_size);
+extern int open_file_direct_io(char *path, int flags, uv_file *file);
 extern char *get_rrdeng_statistics(struct rrdengine_instance *ctx, char *str, size_t size);
 
 #endif /* NETDATA_RRDENGINELIB_H */
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