cache.c: make all io-related functions return errno on error

We'll need proper return-values from these functions to make the cache
behave correctly (which includes giving proper error messages).

Noticed-by: Jim Meyering <jim@meyering.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 22 insertions, 7 deletions

diff --git a/cache.c b/cache.c
index add647e..6847202 100644
--- a/cache.c
+++ b/cache.c
@@ -5,240 +5,255 @@
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  *
  *
  * The cache is just a directory structure where each file is a cache slot,
  * and each filename is based on the hash of some key (e.g. the cgit url).
  * Each file contains the full key followed by the cached content for that
  * key.
  *
  */
 
 #include "cgit.h"
 #include "cache.h"
 
 #define CACHE_BUFSIZE (1024 * 4)
 
 struct cache_slot {
 	const char *key;
 	int keylen;
 	int ttl;
 	cache_fill_fn fn;
 	void *cbdata;
 	int cache_fd;
 	int lock_fd;
 	const char *cache_name;
 	const char *lock_name;
 	int match;
 	struct stat cache_st;
 	struct stat lock_st;
 	int bufsize;
 	char buf[CACHE_BUFSIZE];
 };
 
 /* Open an existing cache slot and fill the cache buffer with
  * (part of) the content of the cache file. Return 0 on success
  * and errno otherwise.
  */
 static int open_slot(struct cache_slot *slot)
 {
 	char *bufz;
 	int bufkeylen = -1;
 
 	slot->cache_fd = open(slot->cache_name, O_RDONLY);
 	if (slot->cache_fd == -1)
 		return errno;
 
 	if (fstat(slot->cache_fd, &slot->cache_st))
 		return errno;
 
 	slot->bufsize = read(slot->cache_fd, slot->buf, sizeof(slot->buf));
 	if (slot->bufsize < 0)
 		return errno;
 
 	bufz = memchr(slot->buf, 0, slot->bufsize);
 	if (bufz)
 		bufkeylen = bufz - slot->buf;
 
 	slot->match = bufkeylen == slot->keylen &&
 	    !memcmp(slot->key, slot->buf, bufkeylen + 1);
 
 	return 0;
 }
 
 /* Close the active cache slot */
-static void close_slot(struct cache_slot *slot)
+static int close_slot(struct cache_slot *slot)
 {
+	int err = 0;
 	if (slot->cache_fd > 0) {
-		close(slot->cache_fd);
+		if (close(slot->cache_fd))
+			err = errno;
+		else
 		slot->cache_fd = -1;
 	}
+	return err;
 }
 
 /* Print the content of the active cache slot (but skip the key). */
 static int print_slot(struct cache_slot *slot)
 {
 	ssize_t i, j = 0;
 
 	i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET);
 	if (i != slot->keylen + 1)
 		return errno;
 
 	while((i=read(slot->cache_fd, slot->buf, sizeof(slot->buf))) > 0)
 		j = write(STDOUT_FILENO, slot->buf, i);
 
 	if (j < 0)
 		return errno;
 	else
 		return 0;
 }
 
 /* Check if the slot has expired */
 static int is_expired(struct cache_slot *slot)
 {
 	if (slot->ttl < 0)
 		return 0;
 	else
 		return slot->cache_st.st_mtime + slot->ttl*60 < time(NULL);
 }
 
 /* Check if the slot has been modified since we opened it.
  * NB: If stat() fails, we pretend the file is modified.
  */
 static int is_modified(struct cache_slot *slot)
 {
 	struct stat st;
 
 	if (stat(slot->cache_name, &st))
 		return 1;
 	return (st.st_ino != slot->cache_st.st_ino ||
 		st.st_mtime != slot->cache_st.st_mtime ||
 		st.st_size != slot->cache_st.st_size);
 }
 
 /* Close an open lockfile */
-static void close_lock(struct cache_slot *slot)
+static int close_lock(struct cache_slot *slot)
 {
+	int err = 0;
 	if (slot->lock_fd > 0) {
-		close(slot->lock_fd);
+		if (close(slot->lock_fd))
+			err = errno;
+		else
 		slot->lock_fd = -1;
 	}
+	return err;
 }
 
 /* Create a lockfile used to store the generated content for a cache
  * slot, and write the slot key + \0 into it.
  * Returns 0 on success and errno otherwise.
  */
 static int lock_slot(struct cache_slot *slot)
 {
 	slot->lock_fd = open(slot->lock_name, O_RDWR|O_CREAT|O_EXCL,
 			     S_IRUSR|S_IWUSR);
 	if (slot->lock_fd == -1)
 		return errno;
-	write(slot->lock_fd, slot->key, slot->keylen + 1);
+	if (write(slot->lock_fd, slot->key, slot->keylen + 1) < 0)
+		return errno;
 	return 0;
 }
 
 /* Release the current lockfile. If `replace_old_slot` is set the
  * lockfile replaces the old cache slot, otherwise the lockfile is
  * just deleted.
  */
 static int unlock_slot(struct cache_slot *slot, int replace_old_slot)
 {
 	int err;
 
 	if (replace_old_slot)
 		err = rename(slot->lock_name, slot->cache_name);
 	else
 		err = unlink(slot->lock_name);
-	return err;
+
+	if (err)
+		return errno;
+
+	return 0;
 }
 
 /* Generate the content for the current cache slot by redirecting
  * stdout to the lock-fd and invoking the callback function
  */
 static int fill_slot(struct cache_slot *slot)
 {
 	int tmp;
 
 	/* Preserve stdout */
 	tmp = dup(STDOUT_FILENO);
 	if (tmp == -1)
 		return errno;
 
 	/* Redirect stdout to lockfile */
 	if (dup2(slot->lock_fd, STDOUT_FILENO) == -1)
 		return errno;
 
 	/* Generate cache content */
 	slot->fn(slot->cbdata);
 
 	/* Restore stdout */
 	if (dup2(tmp, STDOUT_FILENO) == -1)
 		return errno;
 
 	/* Close the temporary filedescriptor */
-	close(tmp);
+	if (close(tmp))
+		return errno;
+
 	return 0;
 }
 
 /* Crude implementation of 32-bit FNV-1 hash algorithm,
  * see http://www.isthe.com/chongo/tech/comp/fnv/ for details
  * about the magic numbers.
  */
 #define FNV_OFFSET 0x811c9dc5
 #define FNV_PRIME  0x01000193
 
 unsigned long hash_str(const char *str)
 {
 	unsigned long h = FNV_OFFSET;
 	unsigned char *s = (unsigned char *)str;
 
 	if (!s)
 		return h;
 
 	while(*s) {
 		h *= FNV_PRIME;
 		h ^= *s++;
 	}
 	return h;
 }
 
 static int process_slot(struct cache_slot *slot)
 {
 	int err;
 
 	err = open_slot(slot);
 	if (!err && slot->match) {
 		if (is_expired(slot)) {
 			if (!lock_slot(slot)) {
 				/* If the cachefile has been replaced between
 				 * `open_slot` and `lock_slot`, we'll just
 				 * serve the stale content from the original
 				 * cachefile. This way we avoid pruning the
 				 * newly generated slot. The same code-path
 				 * is chosen if fill_slot() fails for some
 				 * reason.
 				 *
 				 * TODO? check if the new slot contains the
 				 * same key as the old one, since we would
 				 * prefer to serve the newest content.
 				 * This will require us to open yet another
 				 * file-descriptor and read and compare the
 				 * key from the new file, so for now we're
 				 * lazy and just ignore the new file.
 				 */
 				if (is_modified(slot) || fill_slot(slot)) {
 					unlock_slot(slot, 0);
 					close_lock(slot);
 				} else {
 					close_slot(slot);
 					unlock_slot(slot, 1);
 					slot->cache_fd = slot->lock_fd;
 				}
 			}
 		}
 		print_slot(slot);
 		close_slot(slot);
 		return 0;
 	}