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

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

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/06852f21544c061cb4d4b53bbe16a647a12dd311

Modified Files
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src/backend/storage/ipc/dsm_impl.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)