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Replace pgwin32_is_junction() with lstat().

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Now that lstat() reports junction points with S_IFLNK/S_ISLINK(), and
unlink() can unlink them, there is no need for conditional code for
Windows in a few places.  That was expressed by testing for WIN32 or
S_ISLNK, which we can now constant-fold.

The coding around pgwin32_is_junction() was a bit suspect anyway, as we
never checked for errors, and we also know that errors can be spuriously
reported because of transient sharing violations on this OS.  The
lstat()-based code has handling for that.

This also reverts 4fc6b6ee on master only.  That was done because
lstat() didn't previously work for symlinks (junction points), but now
it does.

Tested-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
(cherry picked from commit 5fc88c5d53e43fa7dcea93499d230a0bf70f4f77)

Author: Thomas Munro <tmunro@postgresql.org>
Author: Alexandra Wang <alexandra.wang.oss@gmail.com>
This commit is contained in:
Thomas Munro 2022-08-06 12:02:43 +12:00 committed by Andrew Dunstan
parent f2a4a137bb
commit f95ad555de
10 changed files with 2 additions and 78 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/backup/basebackup.c
View File

@ -1325,13 +1325,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
}
/* Allow symbolic links in pg_tblspc only */
if (strcmp(path, "./pg_tblspc") == 0 &&
#ifndef WIN32
S_ISLNK(statbuf.st_mode)
#else
pgwin32_is_junction(pathbuf)
#endif
)
if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
{
#if defined(HAVE_READLINK) || defined(WIN32)
char linkpath[MAXPGPATH];
@ -1815,11 +1809,7 @@ static void
convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
{
/* If symlink, write it as a directory anyway */
#ifndef WIN32
if (S_ISLNK(statbuf->st_mode))
#else
if (pgwin32_is_junction(pathbuf))
#endif
statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
}

7
src/backend/commands/tablespace.c
View File

@ -807,8 +807,7 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
/*
* Try to remove the symlink. We must however deal with the possibility
* that it's a directory instead of a symlink --- this could happen during
* WAL replay (see TablespaceCreateDbspace), and it is also the case on
* Windows where junction points lstat() as directories.
* WAL replay (see TablespaceCreateDbspace).
*
* Note: in the redo case, we'll return true if this final step fails;
* there's no point in retrying it. Also, ENOENT should provoke no more
@ -838,7 +837,6 @@ remove_symlink:
linkloc)));
}
}
#ifdef S_ISLNK
else if (S_ISLNK(st.st_mode))
{
if (unlink(linkloc) < 0)
@ -851,7 +849,6 @@ remove_symlink:
linkloc)));
}
}
#endif
else
{
/* Refuse to remove anything that's not a directory or symlink */
@ -929,7 +926,6 @@ remove_tablespace_symlink(const char *linkloc)
errmsg("could not remove directory \"%s\": %m",
linkloc)));
}
#ifdef S_ISLNK
else if (S_ISLNK(st.st_mode))
{
if (unlink(linkloc) < 0 && errno != ENOENT)
@ -938,7 +934,6 @@ remove_tablespace_symlink(const char *linkloc)
errmsg("could not remove symbolic link \"%s\": %m",
linkloc)));
}
#endif
else
{
/* Refuse to remove anything that's not a directory or symlink */

5
src/backend/storage/file/fd.c
View File

@ -3440,7 +3440,6 @@ SyncDataDirectory(void)
*/
xlog_is_symlink = false;
#ifndef WIN32
{
struct stat st;
@ -3452,10 +3451,6 @@ SyncDataDirectory(void)
else if (S_ISLNK(st.st_mode))
xlog_is_symlink = true;
}
#else
if (pgwin32_is_junction("pg_wal"))
xlog_is_symlink = true;
#endif
#ifdef HAVE_SYNCFS
if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_SYNCFS)

7
src/backend/utils/adt/misc.c
View File

@ -283,9 +283,7 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
char sourcepath[MAXPGPATH];
char targetpath[MAXPGPATH];
int rllen;
#ifndef WIN32
struct stat st;
#endif
/*
* It's useful to apply this function to pg_class.reltablespace, wherein
@ -316,10 +314,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
* created with allow_in_place_tablespaces enabled. If a directory is
* found, a relative path to the data directory is returned.
*/
#ifdef WIN32
if (!pgwin32_is_junction(sourcepath))
PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
#else
if (lstat(sourcepath, &st) < 0)
{
ereport(ERROR,
@ -330,7 +324,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
if (!S_ISLNK(st.st_mode))
PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
#endif
/*
* In presence of a link or a junction point, return the path pointing to.

4
src/bin/pg_checksums/pg_checksums.c
View File

@ -388,11 +388,7 @@ scan_directory(const char *basedir, const char *subdir, bool sizeonly)
if (!sizeonly)
scan_file(fn, segmentno);
}
#ifndef WIN32
else if (S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode))
#else
else if (S_ISDIR(st.st_mode) || pgwin32_is_junction(fn))
#endif
{
/*
* If going through the entries of pg_tblspc, we assume to operate

4
src/bin/pg_rewind/file_ops.c
View File

@ -431,11 +431,7 @@ recurse_dir(const char *datadir, const char *parentpath,
/* recurse to handle subdirectories */
recurse_dir(datadir, path, callback);
}
#ifndef WIN32
else if (S_ISLNK(fst.st_mode))
#else
else if (pgwin32_is_junction(fullpath))
#endif
{
#if defined(HAVE_READLINK) || defined(WIN32)
char link_target[MAXPGPATH];

23
src/common/file_utils.c
View File

@ -79,7 +79,6 @@ fsync_pgdata(const char *pg_data,
*/
xlog_is_symlink = false;
#ifndef WIN32
{
struct stat st;
@ -88,10 +87,6 @@ fsync_pgdata(const char *pg_data,
else if (S_ISLNK(st.st_mode))
xlog_is_symlink = true;
}
#else
if (pgwin32_is_junction(pg_wal))
xlog_is_symlink = true;
#endif
/*
* If possible, hint to the kernel that we're soon going to fsync the data
@ -459,27 +454,9 @@ get_dirent_type(const char *path,
result = PGFILETYPE_REG;
else if (S_ISDIR(fst.st_mode))
result = PGFILETYPE_DIR;
#ifdef S_ISLNK
else if (S_ISLNK(fst.st_mode))
result = PGFILETYPE_LNK;
#endif
}
#if defined(WIN32) && !defined(_MSC_VER)
/*
* If we're on native Windows (not Cygwin, which has its own POSIX
* symlinks), but not using the MSVC compiler, then we're using a
* readdir() emulation provided by the MinGW runtime that has no d_type.
* Since the lstat() fallback code reports junction points as directories,
* we need an extra system call to check if we should report them as
* symlinks instead, following our convention.
*/
if (result == PGFILETYPE_DIR &&
!look_through_symlinks &&
pgwin32_is_junction(path))
result = PGFILETYPE_LNK;
#endif
return result;
}

1
src/include/port.h
View File

@ -288,7 +288,6 @@ extern int pgunlink(const char *path);
#if defined(WIN32) && !defined(__CYGWIN__)
extern int pgsymlink(const char *oldpath, const char *newpath);
extern int pgreadlink(const char *path, char *buf, size_t size);
extern bool pgwin32_is_junction(const char *path);
#define symlink(oldpath, newpath) pgsymlink(oldpath, newpath)
#define readlink(path, buf, size) pgreadlink(path, buf, size)

1
src/include/port/win32_port.h
View File

@ -236,7 +236,6 @@ extern pgoff_t _pgftello64(FILE *stream);
*/
extern int pgsymlink(const char *oldpath, const char *newpath);
extern int pgreadlink(const char *path, char *buf, size_t size);
extern bool pgwin32_is_junction(const char *path);
#define symlink(oldpath, newpath) pgsymlink(oldpath, newpath)
#define readlink(path, buf, size) pgreadlink(path, buf, size)

16
src/port/dirmod.c
View File

@ -336,20 +336,4 @@ pgreadlink(const char *path, char *buf, size_t size)
return r;
}
/*
* Assumes the file exists, so will return false if it doesn't
* (since a nonexistent file is not a junction)
*/
bool
pgwin32_is_junction(const char *path)
{
DWORD attr = GetFileAttributes(path);
if (attr == INVALID_FILE_ATTRIBUTES)
{
_dosmaperr(GetLastError());
return false;
}
return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
}
#endif /* defined(WIN32) && !defined(__CYGWIN__) */