From 3f38077d266d089747b468d83d3c936f90ffcabf Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 11 Dec 2023 09:41:27 +1300 Subject: [PATCH v4 2/8] Provide vectored variants of FileRead() and FileWrite(). FileReadV() and FileWriteV() adapt pg_preadv() and pg_pwritev() for fd.c's virtual file descriptors. The simple FileRead() and FileWrite() functions are now implemented in terms of the new functions, to avoid duplicating error and limit logic. The traditional behavior of reporting a "fake" ENOSPC error is preserved, but simplified. It's now always set for non-failing system calls, for the benefit of callers that raise an error with %m for short writes. (We should probably consider getting rid of that expectation.) Reviewed-by: Heikki Linnakangas Discussion: https://postgr.es/m/CA+hUKGJkOiOCa+mag4BF+zHo7qo=o9CFheB8=g6uT5TUm2gkvA@mail.gmail.com --- src/backend/storage/file/fd.c | 43 ++++++++++++++++++++--------------- src/include/storage/fd.h | 32 +++++++++++++++++++++++--- 2 files changed, 54 insertions(+), 21 deletions(-) diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index a185fb3d08..17e910da29 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -2110,18 +2110,18 @@ FileWriteback(File file, off_t offset, off_t nbytes, uint32 wait_event_info) } int -FileRead(File file, void *buffer, size_t amount, off_t offset, - uint32 wait_event_info) +FileReadV(File file, const struct iovec *iov, int iovcnt, off_t offset, + uint32 wait_event_info) { int returnCode; Vfd *vfdP; Assert(FileIsValid(file)); - DO_DB(elog(LOG, "FileRead: %d (%s) " INT64_FORMAT " %zu %p", + DO_DB(elog(LOG, "FileReadV: %d (%s) " INT64_FORMAT " %d", file, VfdCache[file].fileName, (int64) offset, - amount, buffer)); + iovcnt)); returnCode = FileAccess(file); if (returnCode < 0) @@ -2131,7 +2131,7 @@ FileRead(File file, void *buffer, size_t amount, off_t offset, retry: pgstat_report_wait_start(wait_event_info); - returnCode = pg_pread(vfdP->fd, buffer, amount, offset); + returnCode = pg_preadv(vfdP->fd, iov, iovcnt, offset); pgstat_report_wait_end(); if (returnCode < 0) @@ -2166,18 +2166,18 @@ retry: } int -FileWrite(File file, const void *buffer, size_t amount, off_t offset, - uint32 wait_event_info) +FileWriteV(File file, const struct iovec *iov, int iovcnt, off_t offset, + uint32 wait_event_info) { int returnCode; Vfd *vfdP; Assert(FileIsValid(file)); - DO_DB(elog(LOG, "FileWrite: %d (%s) " INT64_FORMAT " %zu %p", + DO_DB(elog(LOG, "FileWriteV: %d (%s) " INT64_FORMAT " %d", file, VfdCache[file].fileName, (int64) offset, - amount, buffer)); + iovcnt)); returnCode = FileAccess(file); if (returnCode < 0) @@ -2195,7 +2195,10 @@ FileWrite(File file, const void *buffer, size_t amount, off_t offset, */ if (temp_file_limit >= 0 && (vfdP->fdstate & FD_TEMP_FILE_LIMIT)) { - off_t past_write = offset + amount; + off_t past_write = offset; + + for (int i = 0; i < iovcnt; ++i) + past_write += iov[i].iov_len; if (past_write > vfdP->fileSize) { @@ -2211,23 +2214,27 @@ FileWrite(File file, const void *buffer, size_t amount, off_t offset, } retry: - errno = 0; pgstat_report_wait_start(wait_event_info); - returnCode = pg_pwrite(VfdCache[file].fd, buffer, amount, offset); + returnCode = pg_pwritev(vfdP->fd, iov, iovcnt, offset); pgstat_report_wait_end(); - /* if write didn't set errno, assume problem is no disk space */ - if (returnCode != amount && errno == 0) - errno = ENOSPC; - if (returnCode >= 0) { + /* + * Some callers expect short writes to set errno, and traditionally we + * have assumed that they imply disk space shortage. We don't want to + * waste CPU cycles adding up the total size here, so we'll just set + * errno to ENOSPC for any successful write (partial or full) in case + * such a caller determines that the write is short. + */ + errno = ENOSPC; + /* * Maintain fileSize and temporary_files_size if it's a temp file. */ if (vfdP->fdstate & FD_TEMP_FILE_LIMIT) { - off_t past_write = offset + amount; + off_t past_write = offset + returnCode; if (past_write > vfdP->fileSize) { @@ -2239,7 +2246,7 @@ retry: else { /* - * See comments in FileRead() + * See comments in FileReadV() */ #ifdef WIN32 DWORD error = GetLastError(); diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h index d9d5d9da5f..f885d0ef15 100644 --- a/src/include/storage/fd.h +++ b/src/include/storage/fd.h @@ -15,7 +15,7 @@ /* * calls: * - * File {Close, Read, Write, Size, Sync} + * File {Close, Read, ReadV, Write, WriteV, Size, Sync} * {Path Name Open, Allocate, Free} File * * These are NOT JUST RENAMINGS OF THE UNIX ROUTINES. @@ -43,6 +43,8 @@ #ifndef FD_H #define FD_H +#include "port/pg_iovec.h" + #include #include @@ -105,8 +107,8 @@ extern File PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fil extern File OpenTemporaryFile(bool interXact); extern void FileClose(File file); extern int FilePrefetch(File file, off_t offset, off_t amount, uint32 wait_event_info); -extern int FileRead(File file, void *buffer, size_t amount, off_t offset, uint32 wait_event_info); -extern int FileWrite(File file, const void *buffer, size_t amount, off_t offset, uint32 wait_event_info); +extern int FileReadV(File file, const struct iovec *ioc, int iovcnt, off_t offset, uint32 wait_event_info); +extern int FileWriteV(File file, const struct iovec *ioc, int iovcnt, off_t offset, uint32 wait_event_info); extern int FileSync(File file, uint32 wait_event_info); extern int FileZero(File file, off_t offset, off_t amount, uint32 wait_event_info); extern int FileFallocate(File file, off_t offset, off_t amount, uint32 wait_event_info); @@ -189,4 +191,28 @@ extern int durable_unlink(const char *fname, int elevel); extern void SyncDataDirectory(void); extern int data_sync_elevel(int elevel); +static inline int +FileRead(File file, void *buffer, size_t amount, off_t offset, + uint32 wait_event_info) +{ + struct iovec iov = { + .iov_base = buffer, + .iov_len = amount + }; + + return FileReadV(file, &iov, 1, offset, wait_event_info); +} + +static inline int +FileWrite(File file, const void *buffer, size_t amount, off_t offset, + uint32 wait_event_info) +{ + struct iovec iov = { + .iov_base = (void *) buffer, + .iov_len = amount + }; + + return FileWriteV(file, &iov, 1, offset, wait_event_info); +} + #endif /* FD_H */ -- 2.39.3 (Apple Git-145)