deltas: Only keep one file open at a time during compilation

Otherwise it's possible for us to exhaust available file descriptors
or (on 32 bit) run up against mmap limits.

In the rollsum case, we didn't need to hold open the "from" object
at all.  And in the bsdiff case, we weren't even looking at either of
the files until we started processing.

Also, while we have the patient open, switch to using O_TMPFILE
if available.

Closes: #567
Approved by: giuseppe

src/libostree/ostree-repo-static-delta-compilation.c

@@ -32,6 +32,7 @@
 #include "ostree-diff.h"
 #include "ostree-rollsum.h"
 #include "otutil.h"
+#include "libglnx.h"
 #include "ostree-varint.h"
 #include "bsdiff/bsdiff.h"
 
@@ -413,15 +414,11 @@ process_one_object (OstreeRepo                       *repo,
 
 typedef struct {
   char *from_checksum;
-  GBytes *tmp_from;
-  GBytes *tmp_to;
 } ContentBsdiff;
 
 typedef struct {
   char *from_checksum;
   OstreeRollsumMatches *matches;
-  GBytes *tmp_from;
-  GBytes *tmp_to;
 } ContentRollsum;
 
 static void
@@ -429,8 +426,6 @@ content_rollsums_free (ContentRollsum  *rollsum)
 {
   g_free (rollsum->from_checksum);
   _ostree_rollsum_matches_free (rollsum->matches);
-  g_clear_pointer (&rollsum->tmp_from, g_bytes_unref);
-  g_clear_pointer (&rollsum->tmp_to, g_bytes_unref);
   g_free (rollsum);
 }
 
@@ -438,8 +433,6 @@ static void
 content_bsdiffs_free (ContentBsdiff  *bsdiff)
 {
   g_free (bsdiff->from_checksum);
-  g_clear_pointer (&bsdiff->tmp_from, g_bytes_unref);
-  g_clear_pointer (&bsdiff->tmp_to, g_bytes_unref);
   g_free (bsdiff);
 }
 
@@ -450,50 +443,40 @@ static gboolean
 get_unpacked_unlinked_content (OstreeRepo       *repo,
                                const char       *checksum,
                                GBytes          **out_content,
-                               GFileInfo       **out_finfo,
                                GCancellable     *cancellable,
                                GError          **error)
 {
-  gboolean ret = FALSE;
+  g_autofree char *tmpname = NULL;
-  g_autofree char *tmpname = g_strdup ("/var/tmp/tmpostree-deltaobj-XXXXXX");
   glnx_fd_close int fd = -1;
   g_autoptr(GBytes) ret_content = NULL;
   g_autoptr(GInputStream) istream = NULL;
-  g_autoptr(GFileInfo) ret_finfo = NULL;
   g_autoptr(GOutputStream) out = NULL;
 
-  fd = g_mkstemp (tmpname);
+  if (!glnx_open_tmpfile_linkable_at (AT_FDCWD, "/tmp", O_RDWR | O_CLOEXEC,
-  if (fd == -1)
+                                      &fd, &tmpname, error))
-    {
+    return FALSE;
-      glnx_set_error_from_errno (error);
+  /* We don't need the file name */
-      goto out;
+  if (tmpname)
-    }
+    (void) unlinkat (AT_FDCWD, tmpname, 0);
-  /* Doesn't need a name */
-  (void) unlink (tmpname);
 
-  if (!ostree_repo_load_file (repo, checksum, &istream, &ret_finfo, NULL,
+  if (!ostree_repo_load_file (repo, checksum, &istream, NULL, NULL,
                               cancellable, error))
-    goto out;
+    return FALSE;
 
-  g_assert (g_file_info_get_file_type (ret_finfo) == G_FILE_TYPE_REGULAR);
-  
   out = g_unix_output_stream_new (fd, FALSE);
   if (g_output_stream_splice (out, istream, G_OUTPUT_STREAM_SPLICE_CLOSE_TARGET,
                               cancellable, error) < 0)
-    goto out;
+    return FALSE;
-  
+
-  { GMappedFile *mfile = g_mapped_file_new_from_fd (fd, FALSE, error);
+  { g_autoptr(GMappedFile) mfile = g_mapped_file_new_from_fd (fd, FALSE, error);
     if (!mfile)
-      goto out;
+      return FALSE;
     ret_content = g_mapped_file_get_bytes (mfile);
-    g_mapped_file_unref (mfile);
   }
 
-  ret = TRUE;
   if (out_content)
     *out_content = g_steal_pointer (&ret_content);
- out:
+  return TRUE;
-  return ret;
 }
 
 static gboolean
@@ -506,22 +489,20 @@ try_content_bsdiff (OstreeRepo                       *repo,
                     GError                           **error)
 {
   gboolean ret = FALSE;
-  g_autoptr(GBytes) tmp_from = NULL;
-  g_autoptr(GBytes) tmp_to = NULL;
   g_autoptr(GFileInfo) from_finfo = NULL;
   g_autoptr(GFileInfo) to_finfo = NULL;
   ContentBsdiff *ret_bsdiff = NULL;
 
   *out_bsdiff = NULL;
 
-  if (!get_unpacked_unlinked_content (repo, from, &tmp_from, &from_finfo,
+  if (!ostree_repo_load_file (repo, from, NULL, &from_finfo, NULL,
-                                      cancellable, error))
+                              cancellable, error))
-    goto out;
+    return FALSE;
-  if (!get_unpacked_unlinked_content (repo, to, &tmp_to, &to_finfo,
+  if (!ostree_repo_load_file (repo, to, NULL, &to_finfo, NULL,
-                                      cancellable, error))
+                              cancellable, error))
-    goto out;
+    return FALSE;
 
-  if (g_bytes_get_size (tmp_to) + g_bytes_get_size (tmp_from) > max_bsdiff_size_bytes)
+  if (g_file_info_get_size (to_finfo) + g_file_info_get_size (from_finfo) > max_bsdiff_size_bytes)
     {
       ret = TRUE;
       goto out;
@@ -529,8 +510,6 @@ try_content_bsdiff (OstreeRepo                       *repo,
 
   ret_bsdiff = g_new0 (ContentBsdiff, 1);
   ret_bsdiff->from_checksum = g_strdup (from);
-  ret_bsdiff->tmp_from = tmp_from; tmp_from = NULL;
-  ret_bsdiff->tmp_to = tmp_to; tmp_to = NULL;
 
   ret = TRUE;
   if (out_bsdiff)
@@ -551,8 +530,6 @@ try_content_rollsum (OstreeRepo                       *repo,
   gboolean ret = FALSE;
   g_autoptr(GBytes) tmp_from = NULL;
   g_autoptr(GBytes) tmp_to = NULL;
-  g_autoptr(GFileInfo) from_finfo = NULL;
-  g_autoptr(GFileInfo) to_finfo = NULL;
   OstreeRollsumMatches *matches = NULL;
   ContentRollsum *ret_rollsum = NULL;
 
@@ -561,11 +538,9 @@ try_content_rollsum (OstreeRepo                       *repo,
   /* Load the content objects, splice them to uncompressed temporary files that
    * we can just mmap() and seek around in conveniently.
    */
-  if (!get_unpacked_unlinked_content (repo, from, &tmp_from, &from_finfo,
+  if (!get_unpacked_unlinked_content (repo, from, &tmp_from, cancellable, error))
-                                      cancellable, error))
     goto out;
-  if (!get_unpacked_unlinked_content (repo, to, &tmp_to, &to_finfo,
+  if (!get_unpacked_unlinked_content (repo, to, &tmp_to, cancellable, error))
-                                      cancellable, error))
     goto out;
 
   matches = _ostree_compute_rollsum_matches (tmp_from, tmp_to);
@@ -592,10 +567,8 @@ try_content_rollsum (OstreeRepo                       *repo,
 
   ret_rollsum = g_new0 (ContentRollsum, 1);
   ret_rollsum->from_checksum = g_strdup (from);
-  ret_rollsum->matches = matches; matches = NULL;
+  ret_rollsum->matches = g_steal_pointer (&matches);
-  ret_rollsum->tmp_from = tmp_from; tmp_from = NULL;
+
-  ret_rollsum->tmp_to = tmp_to; tmp_to = NULL;
-  
   ret = TRUE;
   if (out_rollsum)
     *out_rollsum = g_steal_pointer (&ret_rollsum);
@@ -651,7 +624,7 @@ process_one_rollsum (OstreeRepo                       *repo,
 {
   gboolean ret = FALSE;
   guint64 content_size;
-  g_autoptr(GInputStream) content_stream = NULL;
+  g_autoptr(GBytes) tmp_to = NULL;
   g_autoptr(GFileInfo) content_finfo = NULL;
   g_autoptr(GVariant) content_xattrs = NULL;
   OstreeStaticDeltaPartBuilder *current_part = *current_part_val;
@@ -665,9 +638,13 @@ process_one_rollsum (OstreeRepo                       *repo,
       *current_part_val = current_part = allocate_part (builder);
     }
 
-  tmp_to_buf = g_bytes_get_data (rollsum->tmp_to, &tmp_to_len);
+  if (!get_unpacked_unlinked_content (repo, to_checksum, &tmp_to,
+                                      cancellable, error))
+    goto out;
 
-  if (!ostree_repo_load_file (repo, to_checksum, &content_stream,
+  tmp_to_buf = g_bytes_get_data (tmp_to, &tmp_to_len);
+
+  if (!ostree_repo_load_file (repo, to_checksum, NULL,
                               &content_finfo, &content_xattrs,
                               cancellable, error))
     goto out;
@@ -754,9 +731,6 @@ process_one_rollsum (OstreeRepo                       *repo,
     g_string_append_c (current_part->operations, (gchar)OSTREE_STATIC_DELTA_OP_CLOSE);
   }
 
-  g_clear_pointer (&rollsum->tmp_from, g_bytes_unref);
-  g_clear_pointer (&rollsum->tmp_to, g_bytes_unref);
-
   ret = TRUE;
  out:
   return ret;
@@ -773,10 +747,11 @@ process_one_bsdiff (OstreeRepo                       *repo,
 {
   gboolean ret = FALSE;
   guint64 content_size;
-  g_autoptr(GInputStream) content_stream = NULL;
   g_autoptr(GFileInfo) content_finfo = NULL;
   g_autoptr(GVariant) content_xattrs = NULL;
   OstreeStaticDeltaPartBuilder *current_part = *current_part_val;
+  g_autoptr(GBytes) tmp_from = NULL;
+  g_autoptr(GBytes) tmp_to = NULL;
   const guint8 *tmp_to_buf;
   gsize tmp_to_len;
   const guint8 *tmp_from_buf;
@@ -789,10 +764,17 @@ process_one_bsdiff (OstreeRepo                       *repo,
       *current_part_val = current_part = allocate_part (builder);
     }
 
-  tmp_to_buf = g_bytes_get_data (bsdiff_content->tmp_to, &tmp_to_len);
+  if (!get_unpacked_unlinked_content (repo, bsdiff_content->from_checksum, &tmp_from,
-  tmp_from_buf = g_bytes_get_data (bsdiff_content->tmp_from, &tmp_from_len);
+                                      cancellable, error))
+    goto out;
+  if (!get_unpacked_unlinked_content (repo, to_checksum, &tmp_to,
+                                      cancellable, error))
+    goto out;
 
-  if (!ostree_repo_load_file (repo, to_checksum, &content_stream,
+  tmp_to_buf = g_bytes_get_data (tmp_to, &tmp_to_len);
+  tmp_from_buf = g_bytes_get_data (tmp_from, &tmp_from_len);
+
+  if (!ostree_repo_load_file (repo, to_checksum, NULL,
                               &content_finfo, &content_xattrs,
                               cancellable, error))
     goto out;
@@ -853,9 +835,6 @@ process_one_bsdiff (OstreeRepo                       *repo,
 
   g_string_append_c (current_part->operations, (gchar)OSTREE_STATIC_DELTA_OP_UNSET_READ_SOURCE);
 
-  g_clear_pointer (&bsdiff_content->tmp_from, g_bytes_unref);
-  g_clear_pointer (&bsdiff_content->tmp_to, g_bytes_unref);
-
   ret = TRUE;
  out:
   return ret;