Replace pgwin32_is_junction() with lstat().

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
This commit is contained in:
Thomas Munro 2022-08-06 12:02:43 +12:00
parent f357233c9d
commit 5fc88c5d53
10 changed files with 2 additions and 78 deletions

View File

@ -792,8 +792,7 @@ 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
@ -823,7 +822,6 @@ remove_symlink:
linkloc)));
}
}
#ifdef S_ISLNK
else if (S_ISLNK(st.st_mode))
{
if (unlink(linkloc) < 0)
@ -836,7 +834,6 @@ remove_symlink:
linkloc)));
}
}
#endif
else
{
/* Refuse to remove anything that's not a directory or symlink */
@ -914,7 +911,6 @@ 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)
@ -923,7 +919,6 @@ 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 */

View File

@ -1322,13 +1322,7 @@ 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))
{
char linkpath[MAXPGPATH];
int rllen;
@ -1798,11 +1792,7 @@ 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;
}

View File

@ -3365,7 +3365,6 @@ SyncDataDirectory(void)
*/
xlog_is_symlink = false;
#ifndef WIN32
{
struct stat st;
@ -3377,10 +3376,6 @@ 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)

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
@ -314,10 +312,6 @@ 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,
@ -328,7 +322,6 @@ 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.

View File

@ -384,11 +384,7 @@ 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

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
{
char link_target[MAXPGPATH];
int len;

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;
}

View File

@ -284,7 +284,6 @@ 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)

View File

@ -230,7 +230,6 @@ int setitimer(int which, const struct itimerval *value, struct itimerval *oval
*/
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)

View File

@ -362,20 +362,4 @@ 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__) */