lib: Changed unlink_directory() API to return error string.

There are many different reasons why it could fail, which a simple errno
can't very clearly indicate.

src/lib-storage/list/mailbox-list-delete.c

@@ -48,7 +48,7 @@ int mailbox_list_delete_maildir_via_trash(struct mailbox_list *list,
 					  const char *name,
 					  const char *trash_dir)
 {
-	const char *src, *trash_dest;
+	const char *src, *trash_dest, *error;
 	unsigned int count;
 
 	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
@@ -98,18 +98,18 @@ int mailbox_list_delete_maildir_via_trash(struct mailbox_list *list,
 		if (trash_dir == trash_dest) {
 			trash_dest = t_strconcat(trash_dir, "/",
 						 unique_fname(), NULL);
-		} else if (mailbox_list_delete_trash(trash_dest) < 0 &&
+		} else if (mailbox_list_delete_trash(trash_dest, &error) < 0 &&
 			   (errno != ENOTEMPTY || count >= 5)) {
 			mailbox_list_set_critical(list,
-				"unlink_directory(%s) failed: %m", trash_dest);
+				"unlink_directory(%s) failed: %s", trash_dest, error);
 			return -1;
 		}
 	}
 
-	if (mailbox_list_delete_trash(trash_dir) < 0 &&
+	if (mailbox_list_delete_trash(trash_dir, &error) < 0 &&
 	    errno != ENOTEMPTY && errno != EBUSY) {
 		mailbox_list_set_critical(list,
-			"unlink_directory(%s) failed: %m", trash_dir);
+			"unlink_directory(%s) failed: %s", trash_dir, error);
 
 		/* it's already renamed to trash dir, which means it's
 		   deleted as far as the client is concerned. Report
@@ -145,6 +145,7 @@ int mailbox_list_delete_mailbox_nonrecursive(struct mailbox_list *list,
 	struct dirent *d;
 	string_t *full_path;
 	unsigned int dir_len;
+	const char *error;
 	bool mailbox_dir, unlinked_something = FALSE;
 
 	if (mailbox_list_check_root_delete(list, name, path) < 0)
@@ -185,10 +186,10 @@ int mailbox_list_delete_mailbox_nonrecursive(struct mailbox_list *list,
 		str_append(full_path, d->d_name);
 
 		if (mailbox_dir) {
-			if (mailbox_list_delete_trash(str_c(full_path)) < 0) {
+			if (mailbox_list_delete_trash(str_c(full_path), &error) < 0) {
 				mailbox_list_set_critical(list,
-					"unlink_directory(%s) failed: %m",
-					str_c(full_path));
+					"unlink_directory(%s) failed: %s",
+					str_c(full_path), error);
 			} else {
 				unlinked_something = TRUE;
 			}
@@ -275,7 +276,7 @@ void mailbox_list_delete_until_root(struct mailbox_list *list, const char *path,
 static void mailbox_list_try_delete(struct mailbox_list *list, const char *name,
 				    enum mailbox_list_path_type type)
 {
-	const char *mailbox_path, *path;
+	const char *mailbox_path, *path, *error;
 
 	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
 				  &mailbox_path) <= 0 ||
@@ -292,10 +293,10 @@ static void mailbox_list_try_delete(struct mailbox_list *list, const char *name,
 							     rmdir_path) < 0)
 			return;
 	} else {
-		if (mailbox_list_delete_trash(path) < 0 &&
+		if (mailbox_list_delete_trash(path, &error) < 0 &&
 		    errno != ENOENT && errno != ENOTEMPTY) {
 			mailbox_list_set_critical(list,
-				"unlink_directory(%s) failed: %m", path);
+				"unlink_directory(%s) failed: %s", path, error);
 		}
 	}
 
@@ -310,9 +311,9 @@ void mailbox_list_delete_finish(struct mailbox_list *list, const char *name)
 	mailbox_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX);
 }
 
-int mailbox_list_delete_trash(const char *path)
+int mailbox_list_delete_trash(const char *path, const char **error_r)
 {
-	if (unlink_directory(path, UNLINK_DIRECTORY_FLAG_RMDIR) < 0) {
+	if (unlink_directory(path, UNLINK_DIRECTORY_FLAG_RMDIR, error_r) < 0) {
 		if (errno == ELOOP) {
 			/* it's a symlink? try just deleting it */
 			if (unlink(path) == 0)

src/lib-storage/list/mailbox-list-delete.h

@@ -15,7 +15,7 @@ void mailbox_list_delete_finish(struct mailbox_list *list, const char *name);
 
 void mailbox_list_delete_until_root(struct mailbox_list *list, const char *path,
 				    enum mailbox_list_path_type type);
-int mailbox_list_delete_trash(const char *path);
+int mailbox_list_delete_trash(const char *path, const char **error_r);
 
 int mailbox_list_delete_symlink_default(struct mailbox_list *list,
 					const char *name);

src/lib-storage/list/mailbox-list-index-backend.c

@@ -460,7 +460,7 @@ static void
 index_list_try_delete(struct mailbox_list *_list, const char *name,
 		      enum mailbox_list_path_type type)
 {
-	const char *mailbox_path, *path;
+	const char *mailbox_path, *path, *error;
 
 	if (mailbox_list_get_path(_list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
 				  &mailbox_path) <= 0 ||
@@ -477,10 +477,10 @@ index_list_try_delete(struct mailbox_list *_list, const char *name,
 							     rmdir_path) < 0)
 			return;
 	} else {
-		if (mailbox_list_delete_trash(path) < 0 &&
+		if (mailbox_list_delete_trash(path, &error) < 0 &&
 		    errno != ENOENT && errno != ENOTEMPTY) {
 			mailbox_list_set_critical(_list,
-				"unlink_directory(%s) failed: %m", path);
+				"unlink_directory(%s) failed: %s", path, error);
 		}
 	}
 

src/lib-storage/list/mailbox-list-maildir-iter.c

@@ -245,7 +245,7 @@ int maildir_list_get_mailbox_flags(struct mailbox_list *list,
 static bool maildir_delete_trash_dir(struct maildir_list_iterate_context *ctx,
 				     const char *fname)
 {
-	const char *path;
+	const char *path, *error;
 	struct stat st;
 
 	if (fname[1] != ctx->prefix_char || ctx->prefix_char == '\0' ||
@@ -258,7 +258,7 @@ static bool maildir_delete_trash_dir(struct maildir_list_iterate_context *ctx,
 	path = t_strdup_printf("%s/%s", ctx->dir, fname);
 	if (stat(path, &st) == 0 &&
 	    st.st_mtime < ioloop_time - 3600)
-		(void)mailbox_list_delete_trash(path);
+		(void)mailbox_list_delete_trash(path, &error);
 
 	return TRUE;
 }

src/lib/unlink-directory.c

@@ -33,6 +33,7 @@
 #define _GNU_SOURCE /* for O_NOFOLLOW with Linux */
 
 #include "lib.h"
+#include "abspath.h"
 #include "unlink-directory.h"
 
 #include <fcntl.h>
@@ -41,7 +42,8 @@
 #include <sys/stat.h>
 
 static int
-unlink_directory_r(const char *dir, enum unlink_directory_flags flags)
+unlink_directory_r(const char *dir, enum unlink_directory_flags flags,
+		   const char **error_r)
 {
 	DIR *dirp;
 	struct dirent *d;
@@ -50,30 +52,40 @@ unlink_directory_r(const char *dir, enum unlink_directory_flags flags)
 
 #ifdef O_NOFOLLOW
 	dir_fd = open(dir, O_RDONLY | O_NOFOLLOW);
-	if (dir_fd == -1)
+	if (dir_fd == -1) {
+		*error_r = t_strdup_printf(
+			"open(%s, O_RDONLY | O_NOFOLLOW) failed: %m", dir);
 		return -1;
+	}
 #else
 	struct stat st2;
 
-	if (lstat(dir, &st) < 0)
+	if (lstat(dir, &st) < 0) {
+		*error_r = t_strdup_printf("lstat(%s) failed: %m", dir);
 		return -1;
+	}
 
 	if (!S_ISDIR(st.st_mode)) {
-		if ((st.st_mode & S_IFMT) != S_IFLNK)
+		if ((st.st_mode & S_IFMT) != S_IFLNK) {
+			*error_r = t_strdup_printf("%s is not a directory: %s", dir);
 			errno = ENOTDIR;
-		else {
+		} else {
 			/* be compatible with O_NOFOLLOW */
 			errno = ELOOP;
+			*error_r = t_strdup_printf("%s is a symlink, not a directory: %s", dir);
 		}
 		return -1;
 	}
 
 	dir_fd = open(dir, O_RDONLY);
-	if (dir_fd == -1)
+	if (dir_fd == -1) {
+		*error_r = t_strdup_printf("open(%s, O_RDONLY) failed: %m", dir);
 		return -1;
+	}
 
 	if (fstat(dir_fd, &st2) < 0) {
 		i_close_fd(&dir_fd);
+		*error_r = t_strdup_printf("fstat(%s) failed: %m", dir);
 		return -1;
 	}
 
@@ -82,17 +94,21 @@ unlink_directory_r(const char *dir, enum unlink_directory_flags flags)
 		/* directory was just replaced with something else. */
 		i_close_fd(&dir_fd);
 		errno = ENOTDIR;
+		*error_r = t_strdup_printf(
+			"%s race condition: directory was just replaced", dir);
 		return -1;
 	}
 #endif
 	if (fchdir(dir_fd) < 0) {
                 i_close_fd(&dir_fd);
+		*error_r = t_strdup_printf("fchdir(%s) failed: %m", dir);
 		return -1;
 	}
 
 	dirp = opendir(".");
 	if (dirp == NULL) {
 		i_close_fd(&dir_fd);
+		*error_r = t_strdup_printf("opendir(.) (in %s) failed: %m", dir);
 		return -1;
 	}
 
@@ -117,7 +133,7 @@ unlink_directory_r(const char *dir, enum unlink_directory_flags flags)
 				errno = 0;
 			} else if (S_ISDIR(st.st_mode) &&
 				   (flags & UNLINK_DIRECTORY_FLAG_FILES_ONLY) == 0) {
-				if (unlink_directory_r(d->d_name, flags) < 0) {
+				if (unlink_directory_r(d->d_name, flags, error_r) < 0) {
 					if (errno != ENOENT)
 						break;
 					errno = 0;
@@ -156,33 +172,45 @@ unlink_directory_r(const char *dir, enum unlink_directory_flags flags)
 	old_errno = errno;
 
 	i_close_fd(&dir_fd);
-	if (closedir(dirp) < 0)
+	if (closedir(dirp) < 0) {
+		*error_r = t_strdup_printf("closedir(%s) failed: %m", dir);
 		return -1;
+	}
 
 	if (old_errno != 0) {
 		errno = old_errno;
+		*error_r = t_strdup_printf("readdir(%s) failed: %m", dir);
 		return -1;
 	}
 
 	return 0;
 }
 
-int unlink_directory(const char *dir, enum unlink_directory_flags flags)
+int unlink_directory(const char *dir, enum unlink_directory_flags flags,
+		     const char **error_r)
 {
+	const char *orig_dir;
 	int fd, ret, old_errno;
 
+	if (t_get_current_dir(&orig_dir) < 0)
+		orig_dir = ".";
+
 	fd = open(".", O_RDONLY);
-	if (fd == -1)
+	if (fd == -1) {
+		*error_r = t_strdup_printf(
+			"Can't preserve current directory %s: "
+			"open(.) failed: %m", orig_dir);
 		return -1;
+	}
 
-	ret = unlink_directory_r(dir, flags);
+	ret = unlink_directory_r(dir, flags, error_r);
 	if (ret < 0 && errno == ENOENT)
 		ret = 0;
 	old_errno = errno;
 
 	if (fchdir(fd) < 0) {
 		i_fatal("unlink_directory(%s): "
-			"Can't fchdir() back to our original dir: %m", dir);
+			"Can't fchdir() back to our original dir %s: %m", dir, orig_dir);
 	}
 	i_close_fd(&fd);
 
@@ -193,6 +221,7 @@ int unlink_directory(const char *dir, enum unlink_directory_flags flags)
 
 	if ((flags & UNLINK_DIRECTORY_FLAG_RMDIR) != 0) {
 		if (rmdir(dir) < 0 && errno != ENOENT) {
+			*error_r = t_strdup_printf("rmdir(%s) failed: %m", dir);
 			if (errno == EEXIST) {
 				/* standardize errno */
 				errno = ENOTEMPTY;

src/lib/unlink-directory.h

@@ -11,7 +11,10 @@ enum unlink_directory_flags {
 };
 
 /* Unlink directory and/or everything under it.
-   Returns 0 if successful, -1 if error. */
-int unlink_directory(const char *dir, enum unlink_directory_flags flags);
+   Returns 0 if successful, -1 if error. If the directory doesn't exist,
+   -1 and errno=ENOENT is returned. The returned error message contains the
+   exact syscall that failed, e.g. "open(path) failed: Permission denied" */
+int unlink_directory(const char *dir, enum unlink_directory_flags flags,
+		     const char **error_r);
 
 #endif

src/plugins/fts-lucene/lucene-wrapper.cc

@@ -265,7 +265,7 @@ void lucene_index_unselect_mailbox(struct lucene_index *index)
 static void lucene_handle_error(struct lucene_index *index, CLuceneError &err,
 				const char *msg)
 {
-	const char *what = err.what();
+	const char *error, *what = err.what();
 
 	i_error("lucene index %s: %s failed (#%d): %s",
 		index->path, msg, err.number(), what);
@@ -275,9 +275,9 @@ static void lucene_handle_error(struct lucene_index *index, CLuceneError &err,
 	     err.number() == CL_ERR_IO)) {
 		/* delete corrupted index. most IO errors are also about
 		   missing files and other such corruption.. */
-		if (unlink_directory(index->path, (enum unlink_directory_flags)0) < 0 &&
+		if (unlink_directory(index->path, (enum unlink_directory_flags)0, &error) < 0 &&
 		    errno != ENOENT)
-			i_error("unlink_directory(%s) failed: %m", index->path);
+			i_error("unlink_directory(%s) failed: %s", index->path, error);
 		rescan_clear_unseen_mailboxes(index, NULL);
 	}
 }
@@ -412,6 +412,7 @@ int lucene_index_get_doc_count(struct lucene_index *index, uint32_t *count_r)
 static int lucene_settings_check(struct lucene_index *index)
 {
 	uint32_t set_checksum;
+	const char *error;
 	int ret = 0;
 
 	set_checksum = fts_lucene_settings_checksum(&index->set);
@@ -422,8 +423,8 @@ static int lucene_settings_check(struct lucene_index *index)
 	i_warning("fts-lucene: Settings have changed, rebuilding index for mailbox");
 
 	/* settings changed, rebuild index */
-	if (unlink_directory(index->path, (enum unlink_directory_flags)0) < 0) {
-		i_error("unlink_directory(%s) failed: %m", index->path);
+	if (unlink_directory(index->path, (enum unlink_directory_flags)0, &error) < 0) {
+		i_error("unlink_directory(%s) failed: %s", index->path, error);
 		ret = -1;
 	} else {
 		rescan_clear_unseen_mailboxes(index, NULL);