From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyril Hrubis Date: Thu, 25 Aug 2016 18:53:54 +0200 Subject: [LTP] [PATCH] syscalls/fallocate04: Fix on Btrfs Message-ID: <20160825165354.GA13281@rei> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it The size of a file can double on Btrfs temporarily even when we write into a preallocated space because of internal Btrfs caches, at least that is what I've been told by Btrfs devs. The internal caches are then freed after some time, or can be force freed by syncing the file, which is what this patch does. Technically we are not guaranteed that the file size will not change after writing to preallocated space. We are only guaranteed that subsequent writes to the region will not fail with ENOSPC. So this behavior, while uncommon, is not really a bug. Before the patch the test fails with: fallocate04 0 TINFO : allocate '12288' bytes fallocate04 1 TPASS : test-case succeeded fallocate04 0 TINFO : read allocated file size '24576' fallocate04 0 TINFO : make a hole with FALLOC_FL_PUNCH_HOLE fallocate04 0 TINFO : check that file has a hole with lseek(,,SEEK_HOLE) fallocate04 0 TINFO : found a hole at '4096' offset fallocate04 0 TINFO : allocated file size before '24576' and after '12288' fallocate04 2 TFAIL : fallocate04.c:184: not expected allocated size Signed-off-by: Cyril Hrubis --- testcases/kernel/syscalls/fallocate/fallocate04.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/testcases/kernel/syscalls/fallocate/fallocate04.c b/testcases/kernel/syscalls/fallocate/fallocate04.c index 2b904e4..f204188 100644 --- a/testcases/kernel/syscalls/fallocate/fallocate04.c +++ b/testcases/kernel/syscalls/fallocate/fallocate04.c @@ -75,6 +75,8 @@ static size_t get_allocsize(void) { struct stat file_stat; + fsync(fd); + SAFE_FSTAT(cleanup, fd, &file_stat); return file_stat.st_blocks * 512; -- 2.7.3 -- Cyril Hrubis chrubis@suse.cz