Fix failure-to-read-man-page in commit 899bd785c.

posix_fallocate() is not quite a drop-in replacement for fallocate(),
because it is defined to return the error code as its function result,
not in "errno".  I (tgl) missed this because RHEL6's version seems
to set errno as well.  That is not the case on more modern Linuxen,
though, as per buildfarm results.

Aside from fixing the return-convention confusion, remove the test
for ENOSYS; we expect that glibc will mask that for posix_fallocate,
though it does not for fallocate.  Keep the test for EINTR, because
POSIX specifies that as a possible result, and buildfarm results
suggest that it can happen in practice.

Back-patch to 9.4, like the previous commit.

Thomas Munro

Discussion: https://postgr.es/m/1002664500.12301802.1471008223422.JavaMail.yahoo@mail.yahoo.com

diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index a5879060d0715785db3712da3ce7b02b7052a6f0..b18bea64c6ceea2a866ad15cd45534e5bb50a1e5 100644 (file)
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -425,17 +425,14 @@ dsm_impl_posix_resize(int fd, off_t size)
        do
        {
            rc = posix_fallocate(fd, 0, size);
-       } while (rc == -1 && errno == EINTR);
+       } while (rc == EINTR);
 
-       if (rc != 0 && errno == ENOSYS)
-       {
-           /*
-            * Kernel too old (< 2.6.23).  Rather than fail, just trust that
-            * we won't hit the problem (it typically doesn't show up without
-            * many-GB-sized requests, anyway).
-            */
-           rc = 0;
-       }
+       /*
+        * The caller expects errno to be set, but posix_fallocate() doesn't
+        * set it.  Instead it returns error numbers directly.  So set errno,
+        * even though we'll also return rc to indicate success or failure.
+        */
+       errno = rc;
    }
 #endif                         /* HAVE_POSIX_FALLOCATE && __linux__ */