diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/ipc/dsm_impl.c | 54 | ||||
| -rw-r--r-- | src/include/pg_config.h.in | 3 | ||||
| -rw-r--r-- | src/include/pg_config.h.win32 | 3 |
3 files changed, 58 insertions, 2 deletions
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c index 8482cd86445..db7cc77bb8e 100644 --- a/src/backend/storage/ipc/dsm_impl.c +++ b/src/backend/storage/ipc/dsm_impl.c @@ -73,6 +73,7 @@ static bool dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size, void **impl_private, void **mapped_address, Size *mapped_size, int elevel); +static int dsm_impl_posix_resize(int fd, off_t size); #endif #ifdef USE_DSM_SYSV static bool dsm_impl_sysv(dsm_op op, dsm_handle handle, Size request_size, @@ -319,7 +320,8 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size, } request_size = st.st_size; } - else if (*mapped_size != request_size && ftruncate(fd, request_size)) + else if (*mapped_size != request_size && + dsm_impl_posix_resize(fd, request_size) != 0) { int save_errno; @@ -392,7 +394,55 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size, return true; } -#endif + +/* + * Set the size of a virtual memory region associated with a file descriptor. + * If necessary, also ensure that virtual memory is actually allocated by the + * operating system, to avoid nasty surprises later. + * + * Returns non-zero if either truncation or allocation fails, and sets errno. + */ +static int +dsm_impl_posix_resize(int fd, off_t size) +{ + int rc; + + /* Truncate (or extend) the file to the requested size. */ + rc = ftruncate(fd, size); + + /* + * On Linux, a shm_open fd is backed by a tmpfs file. After resizing with + * ftruncate, the file may contain a hole. Accessing memory backed by a + * hole causes tmpfs to allocate pages, which fails with SIGBUS if there + * is no more tmpfs space available. So we ask tmpfs to allocate pages + * here, so we can fail gracefully with ENOSPC now rather than risking + * SIGBUS later. + */ +#if defined(HAVE_POSIX_FALLOCATE) && defined(__linux__) + if (rc == 0) + { + /* We may get interrupted, if so just retry. */ + do + { + rc = posix_fallocate(fd, 0, size); + } while (rc == -1 && errno == 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; + } + } +#endif /* HAVE_POSIX_FALLOCATE && __linux__ */ + + return rc; +} + +#endif /* USE_DSM_POSIX */ #ifdef USE_DSM_SYSV /* diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in index 650f2dceb74..4c8aa0c571b 100644 --- a/src/include/pg_config.h.in +++ b/src/include/pg_config.h.in @@ -365,6 +365,9 @@ /* Define to 1 if you have the `posix_fadvise' function. */ #undef HAVE_POSIX_FADVISE +/* Define to 1 if you have the `posix_fallocate' function. */ +#undef HAVE_POSIX_FALLOCATE + /* Define to 1 if you have the POSIX signal interface. */ #undef HAVE_POSIX_SIGNALS diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32 index 60f91056af7..7d403e6fbb2 100644 --- a/src/include/pg_config.h.win32 +++ b/src/include/pg_config.h.win32 @@ -261,6 +261,9 @@ /* Define to 1 if you have the <poll.h> header file. */ /* #undef HAVE_POLL_H */ +/* Define to 1 if you have the `posix_fallocate' function. */ +/* #undef HAVE_POSIX_FALLOCATE */ + /* Define to 1 if you have the POSIX signal interface. */ /* #undef HAVE_POSIX_SIGNALS */ |