[PATCH 2/2] new: Centralize file type stat-ing logic
Jani Nikula
jani at nikula.org
Mon May 7 14:14:16 PDT 2012
On May 8, 2012 12:08 AM, "Jani Nikula" <jani at nikula.org> wrote:
>
>
> 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 symlink-handling logic has been replaced by a simple stat fall-through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.
Forgot to add that the general approach seems sensible to me.
>
> 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
> >
> > _______________________________________________
> > notmuch mailing list
> > notmuch at notmuchmail.org
> > http://notmuchmail.org/mailman/listinfo/notmuch
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