Move pg_pwritev_with_retry() to src/common/file_utils.c

This commit moves pg_pwritev_with_retry(), a convenience wrapper of
pg_writev() able to handle partial writes, to common/file_utils.c so
that the frontend code is able to use it.  A first use-case targetted
for this routine is pg_basebackup and pg_receivewal, for the
zero-padding of a newly-initialized WAL segment.  This is used currently
in the backend when the GUC wal_init_zero is enabled (default).

Author: Bharath Rupireddy
Reviewed-by: Nathan Bossart, Thomas Munro
Discussion: https://postgr.es/m/CALj2ACUq7nAb7=bJNbK3yYmp-SZhJcXFR_pLk8un6XgDzDF3OA@mail.gmail.com

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index e4d954578c8a564b1a85e4f8d59473744fa5de93..4151cafec5472a437ca62f0e706e7b6de689ffd4 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -93,7 +93,6 @@
 #include "common/pg_prng.h"
 #include "miscadmin.h"
 #include "pgstat.h"
-#include "port/pg_iovec.h"
 #include "portability/mem.h"
 #include "postmaster/startup.h"
 #include "storage/fd.h"
@@ -3738,67 +3737,3 @@ data_sync_elevel(int elevel)
 {
        return data_sync_retry ? elevel : PANIC;
 }
-
-/*
- * A convenience wrapper for pg_pwritev() that retries on partial write.  If an
- * error is returned, it is unspecified how much has been written.
- */
-ssize_t
-pg_pwritev_with_retry(int fd, const struct iovec *iov, int iovcnt, off_t offset)
-{
-       struct iovec iov_copy[PG_IOV_MAX];
-       ssize_t         sum = 0;
-       ssize_t         part;
-
-       /* We'd better have space to make a copy, in case we need to retry. */
-       if (iovcnt > PG_IOV_MAX)
-       {
-               errno = EINVAL;
-               return -1;
-       }
-
-       for (;;)
-       {
-               /* Write as much as we can. */
-               part = pg_pwritev(fd, iov, iovcnt, offset);
-               if (part < 0)
-                       return -1;
-
-#ifdef SIMULATE_SHORT_WRITE
-               part = Min(part, 4096);
-#endif
-
-               /* Count our progress. */
-               sum += part;
-               offset += part;
-
-               /* Step over iovecs that are done. */
-               while (iovcnt > 0 && iov->iov_len <= part)
-               {
-                       part -= iov->iov_len;
-                       ++iov;
-                       --iovcnt;
-               }
-
-               /* Are they all done? */
-               if (iovcnt == 0)
-               {
-                       /* We don't expect the kernel to write more than requested. */
-                       Assert(part == 0);
-                       break;
-               }
-
-               /*
-                * Move whatever's left to the front of our mutable copy and adjust
-                * the leading iovec.
-                */
-               Assert(iovcnt > 0);
-               memmove(iov_copy, iov, sizeof(*iov) * iovcnt);
-               Assert(iov->iov_len > part);
-               iov_copy[0].iov_base = (char *) iov_copy[0].iov_base + part;
-               iov_copy[0].iov_len -= part;
-               iov = iov_copy;
-       }
-
-       return sum;
-}

diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index df4d6d240c06f99a650659eb2b18f1126c27802f..eac05a13ed524e125c459f95df45c7cfe60732d0 100644 (file)
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -28,6 +28,7 @@
 #ifdef FRONTEND
 #include "common/logging.h"
 #endif
+#include "port/pg_iovec.h"
 
 #ifdef FRONTEND
 
@@ -460,3 +461,69 @@ get_dirent_type(const char *path,
 
        return result;
 }
+
+/*
+ * pg_pwritev_with_retry
+ *
+ * Convenience wrapper for pg_pwritev() that retries on partial write.  If an
+ * error is returned, it is unspecified how much has been written.
+ */
+ssize_t
+pg_pwritev_with_retry(int fd, const struct iovec *iov, int iovcnt, off_t offset)
+{
+       struct iovec iov_copy[PG_IOV_MAX];
+       ssize_t         sum = 0;
+       ssize_t         part;
+
+       /* We'd better have space to make a copy, in case we need to retry. */
+       if (iovcnt > PG_IOV_MAX)
+       {
+               errno = EINVAL;
+               return -1;
+       }
+
+       for (;;)
+       {
+               /* Write as much as we can. */
+               part = pg_pwritev(fd, iov, iovcnt, offset);
+               if (part < 0)
+                       return -1;
+
+#ifdef SIMULATE_SHORT_WRITE
+               part = Min(part, 4096);
+#endif
+
+               /* Count our progress. */
+               sum += part;
+               offset += part;
+
+               /* Step over iovecs that are done. */
+               while (iovcnt > 0 && iov->iov_len <= part)
+               {
+                       part -= iov->iov_len;
+                       ++iov;
+                       --iovcnt;
+               }
+
+               /* Are they all done? */
+               if (iovcnt == 0)
+               {
+                       /* We don't expect the kernel to write more than requested. */
+                       Assert(part == 0);
+                       break;
+               }
+
+               /*
+                * Move whatever's left to the front of our mutable copy and adjust
+                * the leading iovec.
+                */
+               Assert(iovcnt > 0);
+               memmove(iov_copy, iov, sizeof(*iov) * iovcnt);
+               Assert(iov->iov_len > part);
+               iov_copy[0].iov_base = (char *) iov_copy[0].iov_base + part;
+               iov_copy[0].iov_len -= part;
+               iov = iov_copy;
+       }
+
+       return sum;
+}

diff --git a/src/include/common/file_utils.h b/src/include/common/file_utils.h
index 2811744c12f570f1af1b9a9f08422a94bfc4b5d2..2c5dbcb0b1eea59ec2d2f75aa87e6bcd396c48e1 100644 (file)
--- a/src/include/common/file_utils.h
+++ b/src/include/common/file_utils.h
@@ -24,6 +24,8 @@ typedef enum PGFileType
        PGFILETYPE_LNK
 } PGFileType;
 
+struct iovec;                                  /* avoid including port/pg_iovec.h here */
+
 #ifdef FRONTEND
 extern int     fsync_fname(const char *fname, bool isdir);
 extern void fsync_pgdata(const char *pg_data, int serverVersion);
@@ -37,4 +39,9 @@ extern PGFileType get_dirent_type(const char *path,
                                                                  bool look_through_symlinks,
                                                                  int elevel);
 
+extern ssize_t pg_pwritev_with_retry(int fd,
+                                                                        const struct iovec *iov,
+                                                                        int iovcnt,
+                                                                        off_t offset);
+
 #endif                                                 /* FILE_UTILS_H */

diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
index 5a48fccd9c203d6e389b759c212e61b294f7593c..c0a212487d92bdb2644a1b338646e104782cce7c 100644 (file)
--- a/src/include/storage/fd.h
+++ b/src/include/storage/fd.h
@@ -51,8 +51,6 @@ typedef enum RecoveryInitSyncMethod
        RECOVERY_INIT_SYNC_METHOD_SYNCFS
 }                      RecoveryInitSyncMethod;
 
-struct iovec;                                  /* avoid including port/pg_iovec.h here */
-
 typedef int File;
 
 
@@ -178,10 +176,6 @@ extern int pg_fsync_no_writethrough(int fd);
 extern int     pg_fsync_writethrough(int fd);
 extern int     pg_fdatasync(int fd);
 extern void pg_flush_data(int fd, off_t offset, off_t nbytes);
-extern ssize_t pg_pwritev_with_retry(int fd,
-                                                                        const struct iovec *iov,
-                                                                        int iovcnt,
-                                                                        off_t offset);
 extern int     pg_truncate(const char *path, off_t length);
 extern void fsync_fname(const char *fname, bool isdir);
 extern int     fsync_fname_ext(const char *fname, bool isdir, bool ignore_perm, int elevel);