From a28ba23c147def88e552ac5023114ce369b94cde Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Sat, 23 Feb 2019 10:38:05 +1300 Subject: [PATCH] Tolerate ENOSYS failure from sync_file_range(). One unintended consequence of commit 9ccdd7f6 was that Windows WSL users started getting a panic whenever we tried to initiate data flushing with sync_file_range(), because WSL does not implement that system call. Previously, they got a stream of periodic warnings, which was also undesirable but at least ignorable. Prevent the panic by handling ENOSYS specially and skipping promotion via data_sync_elevel(). As a small added bonus, suppress future attempts after the first failure so that the earlier problem with noisy warnings is improved. Perhaps work could be done in a future release to fall back to our other write-back hinting mechanisms on such platforms, but this seems more suitable for back-branches. Back-patch to all supported versions, like 9ccdd7f6. Author: Thomas Munro and James Sewell Tested-by: James Sewell Reported-by: Bruce Klein Discussion: https://postgr.es/m/CA+mCpegfOUph2U4ZADtQT16dfbkjjYNJL1bSTWErsazaFjQW9A@mail.gmail.com --- src/backend/storage/file/fd.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index 213de7698a..d46639d2ed 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -420,6 +420,10 @@ pg_flush_data(int fd, off_t offset, off_t nbytes) #if defined(HAVE_SYNC_FILE_RANGE) { int rc; + static bool not_implemented_by_kernel = false; + + if (not_implemented_by_kernel) + return; /* * sync_file_range(SYNC_FILE_RANGE_WRITE), currently linux specific, @@ -434,7 +438,22 @@ pg_flush_data(int fd, off_t offset, off_t nbytes) SYNC_FILE_RANGE_WRITE); if (rc != 0) { - ereport(data_sync_elevel(WARNING), + int elevel; + + /* + * For systems that don't have an implementation of + * sync_file_range() such as Windows WSL, generate only one + * warning and then suppress all further attempts by this process. + */ + if (errno == ENOSYS) + { + elevel = WARNING; + not_implemented_by_kernel = true; + } + else + elevel = data_sync_elevel(WARNING); + + ereport(elevel, (errcode_for_file_access(), errmsg("could not flush dirty data: %m"))); } -- 2.20.1