Flush after opened file size is shrinked

.gitignore

@@ -42,6 +42,7 @@ config.status
 config.sub
 configure
 configure.scan
+configure.ac~
 depcomp
 install-sh
 libtool
@@ -86,6 +87,7 @@ test/junk_data
 test/s3proxy-*
 test/write_multiblock
 test/mknod_test
+test/truncate_read_file
 
 #
 # Windows ports

src/s3fs.cpp

@@ -2563,6 +2563,7 @@ static int s3fs_truncate(const char* _path, off_t size)
     // Get file information
     if(0 == (result = get_object_attribute(path, NULL, &meta))){
         // File exists
+        off_t cur_size = get_size(meta);
 
         // [NOTE]
         // If the file exists, the file has already been opened by FUSE before
@@ -2596,20 +2597,34 @@ static int s3fs_truncate(const char* _path, off_t size)
         }
         ent->UpdateCtime();
 
-#if defined(__APPLE__)
         // [NOTE]
-        // Only for macos, this truncate calls to "size=0" do not reflect size.
-        // The cause is unknown now, but it can be avoided by flushing the file.
+        // In the case of reducing the file size, the stats information on the server
+        // side must be updated.
+        // This is because truncate is called, but flush (sync) is not performed, and
+        // when reading is performed by another process etc. until that flush, the file
+        // size resets to original size and the correct(reduced) file size cannot be
+        // reflected.
         //
-        if(0 == size){
+        if(size < cur_size){
             if(0 != (result = ent->Flush(autoent.GetPseudoFd(), AutoLock::NONE, true))){
                 S3FS_PRN_ERR("could not upload file(%s): result=%d", path, result);
                 return result;
             }
             StatCache::getStatCacheData()->DelStat(path);
-        }
-#endif
 
+#if defined(__APPLE__)
+        }else if(0 == size){
+            // [NOTE]
+            // Only for macos, this truncate calls to "size=0" do not reflect size.
+            // The cause is unknown now, but it can be avoided by flushing the file.
+            //
+            if(0 != (result = ent->Flush(autoent.GetPseudoFd(), AutoLock::NONE, true))){
+                S3FS_PRN_ERR("could not upload file(%s): result=%d", path, result);
+                return result;
+            }
+            StatCache::getStatCacheData()->DelStat(path);
+#endif
+        }
     }else{
         // Not found -> Make tmpfile(with size)
         struct fuse_context* pcxt;

test/Makefile.am

@@ -32,11 +32,13 @@ testdir = test
 noinst_PROGRAMS = \
     junk_data \
     write_multiblock \
-    mknod_test
+    mknod_test \
+    truncate_read_file
 
-junk_data_SOURCES = junk_data.c
-write_multiblock_SOURCES = write_multiblock.cc
-mknod_test_SOURCES = mknod_test.c
+junk_data_SOURCES          = junk_data.c
+write_multiblock_SOURCES   = write_multiblock.cc
+mknod_test_SOURCES         = mknod_test.c
+truncate_read_file_SOURCES = truncate_read_file.c
 
 #
 # Local variables:

test/integration-test-main.sh

@@ -112,6 +112,29 @@ function test_truncate_shrink_file {
     rm_test_file "${BIG_TRUNCATE_TEST_FILE}"
 }
 
+function test_truncate_shrink_read_file {
+    describe "Testing truncate(shrink) and read file ..."
+
+    # Initiate file size is 1024, and shrink file size is 512
+    local init_size=1024
+    local shrink_size=512
+
+    # create file
+    dd if=/dev/urandom of="${TEST_TEXT_FILE}" bs="${init_size}" count=1
+
+    # truncate(shrink) file and read it before flusing
+    ../../truncate_read_file "${TEST_TEXT_FILE}" "${shrink_size}"
+
+    # check file size
+    check_file_size "${TEST_TEXT_FILE}" "${shrink_size}"
+
+
+    # Truncate the file to 1024 length
+    local t_size=1024
+
+    rm_test_file
+}
+
 function test_mv_file {
     describe "Testing mv file function ..."
     # if the rename file exists, delete it
@@ -2610,6 +2633,7 @@ function add_all_tests {
     add_tests test_truncate_upload
     add_tests test_truncate_empty_file
     add_tests test_truncate_shrink_file
+    add_tests test_truncate_shrink_read_file
     add_tests test_mv_file
     add_tests test_mv_to_exist_file
     add_tests test_mv_empty_directory

test/truncate_read_file.c

@@ -0,0 +1,81 @@
+/*
+ * s3fs - FUSE-based file system backed by Amazon S3
+ *
+ * Copyright(C) 2021 Andrew Gaul <andrew@gaul.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+       
+// [NOTE]
+// This is a program used for file size inspection.
+// File size checking should be done by the caller of this program.
+// This program truncates the file and reads the file in another process
+// between truncate and flush(close file).
+//
+int main(int argc, char *argv[])
+{
+    if (argc != 3) {
+        fprintf(stderr, "[ERROR] Wrong paraemters\n");
+        fprintf(stdout, "[Usage] truncate_read_file <file path> <truncate size(bytes)>\n");
+        exit(EXIT_FAILURE);
+    }
+
+    const char* filepath = argv[1];
+    off_t       size     = (off_t)strtoull(argv[2], NULL, 10);
+    int         fd;
+
+    // open file
+    if(-1 == (fd = open(filepath, O_RDWR))){
+        fprintf(stderr, "[ERROR] Could not open file(%s)\n", filepath);
+        exit(EXIT_FAILURE);
+    }
+
+    // truncate
+    if(0 != ftruncate(fd, size)){
+        fprintf(stderr, "[ERROR] Could not truncate file(%s) to %lld byte.\n", filepath, (long long)size);
+        close(fd);
+        exit(EXIT_FAILURE);
+    }
+
+    // run sub-process for reading file(cat)
+    char szCommand[1024];
+    sprintf(szCommand, "cat %s >/dev/null 2>&1", filepath);
+    if(0 != system(szCommand)){
+        fprintf(stderr, "[ERROR] Failed to run sub-process(cat).\n");
+        close(fd);
+        exit(EXIT_FAILURE);
+    }
+
+    // close file(flash)
+    close(fd);
+
+    exit(EXIT_SUCCESS);
+}
+
+/*
+* Local variables:
+* tab-width: 4
+* c-basic-offset: 4
+* End:
+* vim600: expandtab sw=4 ts=4 fdm=marker
+* vim<600: expandtab sw=4 ts=4
+*/