[PATCH 2/2] new: Centralize file type stat-ing logic
Jani Nikula
jani at nikula.org
Mon May 7 14:08:35 PDT 2012
On May 7, 2012 9:10 PM, "Austin Clements" <amdragon at mit.edu> wrote:
>
> This moves our logic to get a file's type into one function. This has
> several benefits: we can support OSes and file systems that do not
> provide dirent.d_type or always return DT_UNKNOWN, complex
> symlink-handling logic has been replaced by a simple stat fall-through
> in one place, and the error message for un-stat-able file is more
> accurate (previously, the error always mentioned directories, even
> though a broken symlink is not a directory).
Please find some quick drive-by-review below.
J.
> ---
> notmuch-new.c | 99
++++++++++++++++++++++++++++++++++-----------------------
> test/new | 2 +-
> 2 files changed, 60 insertions(+), 41 deletions(-)
>
> diff --git a/notmuch-new.c b/notmuch-new.c
> index cb720cc..cf2580e 100644
> --- a/notmuch-new.c
> +++ b/notmuch-new.c
> @@ -154,6 +154,44 @@ dirent_sort_strcmp_name (const struct dirent **a,
const struct dirent **b)
> return strcmp ((*a)->d_name, (*b)->d_name);
> }
>
> +/* Return the type of a directory entry relative to path as a stat(2)
> + * mode. Like stat, this follows symlinks. Returns -1 and sets errno
> + * if the file's type cannot be determined (which includes dangling
> + * symlinks).
> + */
> +static int
> +dirent_type (const char *path, const struct dirent *entry)
> +{
> + struct stat statbuf;
> + char *abspath;
> + int err;
> +
> +#ifdef _DIRENT_HAVE_D_TYPE
> + /* Mapping from d_type to stat mode_t. We omit DT_LNK so that
> + * we'll fall through to stat and get the real file type. */
> + static const mode_t modes[] = {
> + [DT_BLK] = S_IFBLK,
> + [DT_CHR] = S_IFCHR,
> + [DT_DIR] = S_IFDIR,
> + [DT_FIFO] = S_IFIFO,
> + [DT_REG] = S_IFREG,
> + [DT_SOCK] = S_IFSOCK
> + };
> + if (entry->d_type < sizeof(modes)/sizeof(modes[0]) &&
ARRAY_SIZE()
> + modes[entry->d_type])
> + return modes[entry->d_type];
> +#endif
> +
> + abspath = talloc_asprintf (NULL, "%s/%s", path, entry->d_name);
> + if (!abspath)
> + return -1;
Does talloc set errno in this case? I suspect not.
> + err = stat(abspath, &statbuf);
> + talloc_free (abspath);
This likely breaks your promise about errno. You can't trust talloc_free()
not calling some function that sets errno.
> + if (err < 0)
> + return -1;
> + return statbuf.st_mode & S_IFMT;
> +}
> +
> /* Test if the directory looks like a Maildir directory.
> *
> * Search through the array of directory entries to see if we can find all
> @@ -162,12 +200,12 @@ dirent_sort_strcmp_name (const struct dirent **a,
const struct dirent **b)
> * Return 1 if the directory looks like a Maildir and 0 otherwise.
> */
> static int
> -_entries_resemble_maildir (struct dirent **entries, int count)
> +_entries_resemble_maildir (const char *path, struct dirent **entries,
int count)
> {
> int i, found = 0;
>
> for (i = 0; i < count; i++) {
> - if (entries[i]->d_type != DT_DIR && entries[i]->d_type !=
DT_UNKNOWN)
> + if (dirent_type (path, entries[i]) != S_IFDIR)
> continue;
>
> if (strcmp(entries[i]->d_name, "new") == 0 ||
> @@ -250,7 +288,7 @@ add_files_recursive (notmuch_database_t *notmuch,
> notmuch_status_t status, ret = NOTMUCH_STATUS_SUCCESS;
> notmuch_message_t *message = NULL;
> struct dirent **fs_entries = NULL;
> - int i, num_fs_entries;
> + int i, num_fs_entries, entry_type;
> notmuch_directory_t *directory;
> notmuch_filenames_t *db_files = NULL;
> notmuch_filenames_t *db_subdirs = NULL;
> @@ -317,7 +355,7 @@ add_files_recursive (notmuch_database_t *notmuch,
> }
>
> /* Pass 1: Recurse into all sub-directories. */
> - is_maildir = _entries_resemble_maildir (fs_entries, num_fs_entries);
> + is_maildir = _entries_resemble_maildir (path, fs_entries,
num_fs_entries);
>
> for (i = 0; i < num_fs_entries; i++) {
> if (interrupted)
> @@ -325,17 +363,16 @@ add_files_recursive (notmuch_database_t *notmuch,
>
> entry = fs_entries[i];
>
> - /* We only want to descend into directories.
> - * But symlinks can be to directories too, of course.
> - *
> - * And if the filesystem doesn't tell us the file type in the
> - * scandir results, then it might be a directory (and if not,
> - * then we'll stat and return immediately in the next level of
> - * recursion). */
> - if (entry->d_type != DT_DIR &&
> - entry->d_type != DT_LNK &&
> - entry->d_type != DT_UNKNOWN)
> - {
> + /* We only want to descend into directories (and symlinks to
> + * directories). */
> + entry_type = dirent_type (path, entry);
> + if (entry_type == -1) {
> + /* Be pessimistic, e.g. so we don't loose lots of mail
s/loose/lose/ ?
> + * just because a user broke a symlink. */
> + fprintf (stderr, "Error reading file %s/%s: %s\n",
> + path, entry->d_name, strerror (errno));
You can't trust errno here, as explained above.
> + return NOTMUCH_STATUS_FILE_ERROR;
> + } else if (entry_type != S_IFDIR) {
> continue;
> }
>
> @@ -425,31 +462,13 @@ add_files_recursive (notmuch_database_t *notmuch,
> notmuch_filenames_move_to_next (db_subdirs);
> }
>
> - /* If we're looking at a symlink, we only want to add it if it
> - * links to a regular file, (and not to a directory, say).
> - *
> - * Similarly, if the file is of unknown type (due to filesystem
> - * limitations), then we also need to look closer.
> - *
> - * In either case, a stat does the trick.
> - */
> - if (entry->d_type == DT_LNK || entry->d_type == DT_UNKNOWN) {
> - int err;
> -
> - next = talloc_asprintf (notmuch, "%s/%s", path,
entry->d_name);
> - err = stat (next, &st);
> - talloc_free (next);
> - next = NULL;
> -
> - /* Don't emit an error for a link pointing nowhere, since
> - * the directory-traversal pass will have already done
> - * that. */
> - if (err)
> - continue;
> -
> - if (! S_ISREG (st.st_mode))
> - continue;
> - } else if (entry->d_type != DT_REG) {
> + /* Only add regular files (and symlinks to regular files). */
> + entry_type = dirent_type (path, entry);
> + if (entry_type == -1) {
> + fprintf (stderr, "Error reading file %s/%s: %s\n",
> + path, entry->d_name, strerror (errno));
Ditto.
> + return NOTMUCH_STATUS_FILE_ERROR;
> + } else if (entry_type != S_IFREG) {
> continue;
> }
>
> diff --git a/test/new b/test/new
> index 26253db..e3900f5 100755
> --- a/test/new
> +++ b/test/new
> @@ -140,7 +140,7 @@ test_begin_subtest "Broken symlink aborts"
> ln -s does-not-exist "${MAIL_DIR}/broken"
> output=$(NOTMUCH_NEW 2>&1)
> test_expect_equal "$output" \
> -"Error reading directory /run/shm/nm/tmp.new/mail/broken: No such file
or directory
> +"Error reading file /run/shm/nm/tmp.new/mail/broken: No such file or
directory
> Note: A fatal error was encountered: Something went wrong trying to read
or write a file
> No new mail."
> rm "${MAIL_DIR}/broken"
> --
> 1.7.10
>
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> notmuch at notmuchmail.org
> http://notmuchmail.org/mailman/listinfo/notmuch
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