Merge branch 'sp/maint-fd-limit' into maint

* sp/maint-fd-limit:
  sha1_file.c: Don't retain open fds on small packs
  mingw: add minimum getrlimit() compatibility stub
  Limit file descriptors used by packs

cache.h

@@ -898,7 +898,8 @@ extern struct packed_git {
 	time_t mtime;
 	int pack_fd;
 	unsigned pack_local:1,
-		 pack_keep:1;
+		 pack_keep:1,
+		 do_not_close:1;
 	unsigned char sha1[20];
 	/* something like ".git/objects/pack/xxxxx.pack" */
 	char pack_name[FLEX_ARRAY]; /* more */

compat/mingw.h

@@ -233,6 +233,22 @@ int mingw_getpagesize(void);
 #define getpagesize mingw_getpagesize
 #endif
 
+struct rlimit {
+	unsigned int rlim_cur;
+};
+#define RLIMIT_NOFILE 0
+
+static inline int getrlimit(int resource, struct rlimit *rlp)
+{
+	if (resource != RLIMIT_NOFILE) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	rlp->rlim_cur = 2048;
+	return 0;
+}
+
 /* Use mingw_lstat() instead of lstat()/stat() and
  * mingw_fstat() instead of fstat() on Windows.
  */

fast-import.c

@@ -857,6 +857,7 @@ static void start_packfile(void)
 	p = xcalloc(1, sizeof(*p) + strlen(tmpfile) + 2);
 	strcpy(p->pack_name, tmpfile);
 	p->pack_fd = pack_fd;
+	p->do_not_close = 1;
 	pack_file = sha1fd(pack_fd, p->pack_name);
 
 	hdr.hdr_signature = htonl(PACK_SIGNATURE);

sha1_file.c

@@ -417,6 +417,8 @@ static unsigned int pack_used_ctr;
 static unsigned int pack_mmap_calls;
 static unsigned int peak_pack_open_windows;
 static unsigned int pack_open_windows;
+static unsigned int pack_open_fds;
+static unsigned int pack_max_fds;
 static size_t peak_pack_mapped;
 static size_t pack_mapped;
 struct packed_git *packed_git;
@@ -594,8 +596,10 @@ static int unuse_one_window(struct packed_git *current, int keep_fd)
 			lru_l->next = lru_w->next;
 		else {
 			lru_p->windows = lru_w->next;
-			if (!lru_p->windows && lru_p->pack_fd != keep_fd) {
+			if (!lru_p->windows && lru_p->pack_fd != -1
+				&& lru_p->pack_fd != keep_fd) {
 				close(lru_p->pack_fd);
+				pack_open_fds--;
 				lru_p->pack_fd = -1;
 			}
 		}
@@ -680,8 +684,10 @@ void free_pack_by_name(const char *pack_name)
 		if (strcmp(pack_name, p->pack_name) == 0) {
 			clear_delta_base_cache();
 			close_pack_windows(p);
-			if (p->pack_fd != -1)
+			if (p->pack_fd != -1) {
 				close(p->pack_fd);
+				pack_open_fds--;
+			}
 			close_pack_index(p);
 			free(p->bad_object_sha1);
 			*pp = p->next;
@@ -707,9 +713,29 @@ static int open_packed_git_1(struct packed_git *p)
 	if (!p->index_data && open_pack_index(p))
 		return error("packfile %s index unavailable", p->pack_name);
 
+	if (!pack_max_fds) {
+		struct rlimit lim;
+		unsigned int max_fds;
+
+		if (getrlimit(RLIMIT_NOFILE, &lim))
+			die_errno("cannot get RLIMIT_NOFILE");
+
+		max_fds = lim.rlim_cur;
+
+		/* Save 3 for stdin/stdout/stderr, 22 for work */
+		if (25 < max_fds)
+			pack_max_fds = max_fds - 25;
+		else
+			pack_max_fds = 1;
+	}
+
+	while (pack_max_fds <= pack_open_fds && unuse_one_window(NULL, -1))
+		; /* nothing */
+
 	p->pack_fd = git_open_noatime(p->pack_name, p);
 	if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
 		return -1;
+	pack_open_fds++;
 
 	/* If we created the struct before we had the pack we lack size. */
 	if (!p->pack_size) {
@@ -761,6 +787,7 @@ static int open_packed_git(struct packed_git *p)
 		return 0;
 	if (p->pack_fd != -1) {
 		close(p->pack_fd);
+		pack_open_fds--;
 		p->pack_fd = -1;
 	}
 	return -1;
@@ -786,14 +813,13 @@ unsigned char *use_pack(struct packed_git *p,
 {
 	struct pack_window *win = *w_cursor;
 
-	if (p->pack_fd == -1 && open_packed_git(p))
-		die("packfile %s cannot be accessed", p->pack_name);
-
 	/* Since packfiles end in a hash of their content and it's
 	 * pointless to ask for an offset into the middle of that
 	 * hash, and the in_window function above wouldn't match
 	 * don't allow an offset too close to the end of the file.
 	 */
+	if (!p->pack_size && p->pack_fd == -1 && open_packed_git(p))
+		die("packfile %s cannot be accessed", p->pack_name);
 	if (offset > (p->pack_size - 20))
 		die("offset beyond end of packfile (truncated pack?)");
 
@@ -807,6 +833,10 @@ unsigned char *use_pack(struct packed_git *p,
 		if (!win) {
 			size_t window_align = packed_git_window_size / 2;
 			off_t len;
+
+			if (p->pack_fd == -1 && open_packed_git(p))
+				die("packfile %s cannot be accessed", p->pack_name);
+
 			win = xcalloc(1, sizeof(*win));
 			win->offset = (offset / window_align) * window_align;
 			len = p->pack_size - win->offset;
@@ -824,6 +854,12 @@ unsigned char *use_pack(struct packed_git *p,
 				die("packfile %s cannot be mapped: %s",
 					p->pack_name,
 					strerror(errno));
+			if (!win->offset && win->len == p->pack_size
+				&& !p->do_not_close) {
+				close(p->pack_fd);
+				pack_open_fds--;
+				p->pack_fd = -1;
+			}
 			pack_mmap_calls++;
 			pack_open_windows++;
 			if (pack_mapped > peak_pack_mapped)
@@ -918,6 +954,9 @@ struct packed_git *parse_pack_index(unsigned char *sha1, const char *idx_path)
 
 void install_packed_git(struct packed_git *pack)
 {
+	if (pack->pack_fd != -1)
+		pack_open_fds++;
+
 	pack->next = packed_git;
 	packed_git = pack;
 }
@@ -935,8 +974,6 @@ static void prepare_packed_git_one(char *objdir, int local)
 	sprintf(path, "%s/pack", objdir);
 	len = strlen(path);
 	dir = opendir(path);
-	while (!dir && errno == EMFILE && unuse_one_window(NULL, -1))
-		dir = opendir(path);
 	if (!dir) {
 		if (errno != ENOENT)
 			error("unable to open object pack directory: %s: %s",
@@ -1092,14 +1129,6 @@ static int git_open_noatime(const char *name, struct packed_git *p)
 		if (fd >= 0)
 			return fd;
 
-		/* Might the failure be insufficient file descriptors? */
-		if (errno == EMFILE) {
-			if (unuse_one_window(p, -1))
-				continue;
-			else
-				return -1;
-		}
-
 		/* Might the failure be due to O_NOATIME? */
 		if (errno != ENOENT && sha1_file_open_flag) {
 			sha1_file_open_flag = 0;
@@ -1931,6 +1960,27 @@ off_t find_pack_entry_one(const unsigned char *sha1,
 	return 0;
 }
 
+static int is_pack_valid(struct packed_git *p)
+{
+	/* An already open pack is known to be valid. */
+	if (p->pack_fd != -1)
+		return 1;
+
+	/* If the pack has one window completely covering the
+	 * file size, the pack is known to be valid even if
+	 * the descriptor is not currently open.
+	 */
+	if (p->windows) {
+		struct pack_window *w = p->windows;
+
+		if (!w->offset && w->len == p->pack_size)
+			return 1;
+	}
+
+	/* Force the pack to open to prove its valid. */
+	return !open_packed_git(p);
+}
+
 static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 {
 	static struct packed_git *last_found = (void *)1;
@@ -1960,7 +2010,7 @@ static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 			 * it may have been deleted since the index
 			 * was loaded!
 			 */
-			if (p->pack_fd == -1 && open_packed_git(p)) {
+			if (!is_pack_valid(p)) {
 				error("packfile %s cannot be accessed", p->pack_name);
 				goto next;
 			}
@@ -2359,8 +2409,6 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 
 	filename = sha1_file_name(sha1);
 	fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
-	while (fd < 0 && errno == EMFILE && unuse_one_window(NULL, -1))
-		fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
 	if (fd < 0) {
 		if (errno == EACCES)
 			return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());