From d1e67645a26ee0f16cd48957c164cd29878b558f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Sat, 4 Jun 2022 02:04:55 +0300
Subject: [PATCH] mdbx: refine handling `EACCESS` while trying create LCK-file
 on a read-only filesystem.

---
 src/core.c | 30 +++++++++++++++++++++---------
 src/osal.c | 23 ++++++++++++++++++-----
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/src/core.c b/src/core.c
index 674c4c78..e691f6d6 100644
--- a/src/core.c
+++ b/src/core.c
@@ -12440,17 +12440,29 @@ __cold static int mdbx_setup_lck(MDBX_env *env, char *lck_pathname,
 
   int err = mdbx_openfile(MDBX_OPEN_LCK, env, lck_pathname, &env->me_lfd, mode);
   if (err != MDBX_SUCCESS) {
-    if (!(err == MDBX_ENOFILE && (env->me_flags & MDBX_EXCLUSIVE)) &&
-        !((err == MDBX_EROFS || err == MDBX_EACCESS || err == MDBX_EPERM) &&
-          (env->me_flags & MDBX_RDONLY)))
+    switch (err) {
+    default:
       return err;
+    case MDBX_ENOFILE:
+    case MDBX_EACCESS:
+    case MDBX_EPERM:
+      if (!F_ISSET(env->me_flags, MDBX_RDONLY | MDBX_EXCLUSIVE))
+        return err;
+      break;
+    case MDBX_EROFS:
+      if ((env->me_flags & MDBX_RDONLY) == 0)
+        return err;
+      break;
+    }
 
-    /* ensure the file system is read-only */
-    err = mdbx_check_fs_rdonly(env->me_lazy_fd, lck_pathname, err);
-    if (err != MDBX_SUCCESS &&
-        /* ignore ERROR_NOT_SUPPORTED for exclusive mode */
-        !(err == MDBX_ENOSYS && (env->me_flags & MDBX_EXCLUSIVE)))
-      return err;
+    if (err != MDBX_ENOFILE) {
+      /* ensure the file system is read-only */
+      err = mdbx_check_fs_rdonly(env->me_lazy_fd, lck_pathname, err);
+      if (err != MDBX_SUCCESS &&
+          /* ignore ERROR_NOT_SUPPORTED for exclusive mode */
+          !(err == MDBX_ENOSYS && (env->me_flags & MDBX_EXCLUSIVE)))
+        return err;
+    }
 
     /* LY: without-lck mode (e.g. exclusive or on read-only filesystem) */
     /* beginning of a locked section ---------------------------------------- */
diff --git a/src/osal.c b/src/osal.c
index c4622c9b..5a4d32eb 100644
--- a/src/osal.c
+++ b/src/osal.c
@@ -610,8 +610,15 @@ MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
 
   *fd = CreateFileW(pathnameW, DesiredAccess, ShareMode, NULL,
                     CreationDisposition, FlagsAndAttributes, NULL);
-  if (*fd == INVALID_HANDLE_VALUE)
-    return (int)GetLastError();
+  if (*fd == INVALID_HANDLE_VALUE) {
+    int err = (int)GetLastError();
+    if (err == ERROR_ACCESS_DENIED && purpose == MDBX_OPEN_LCK) {
+      if (GetFileAttributesW(pathnameW) == INVALID_FILE_ATTRIBUTES &&
+          GetLastError() == ERROR_FILE_NOT_FOUND)
+        err = ERROR_FILE_NOT_FOUND;
+    }
+    return err;
+  }
 
   BY_HANDLE_FILE_INFORMATION info;
   if (!GetFileInformationByHandle(*fd, &info)) {
@@ -706,6 +713,12 @@ MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
   }
 #endif /* O_DIRECT */
 
+  if (*fd < 0 && errno == EACCES && purpose == MDBX_OPEN_LCK) {
+    struct stat unused;
+    if (stat(pathname, &unused) == 0 || errno != ENOENT)
+      errno = EACCES /* restore errno if file exists */;
+  }
+
   /* Safeguard for todo4recovery://erased_by_github/libmdbx/issues/144 */
 #if STDIN_FILENO == 0 && STDOUT_FILENO == 1 && STDERR_FILENO == 2
   if (*fd == STDIN_FILENO) {
@@ -1091,10 +1104,10 @@ MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
 #else
   struct statvfs info;
   if (err != MDBX_ENOFILE) {
-    if (statvfs(pathname, &info))
-      return errno;
-    if ((info.f_flag & ST_RDONLY) == 0)
+    if (statvfs(pathname, &info) == 0 && (info.f_flag & ST_RDONLY) == 0)
       return err;
+    if (errno != MDBX_ENOFILE)
+      return errno;
   }
   if (fstatvfs(handle, &info))
     return errno;