Fix data_offset when importing the indexes

When importing an index, we don't have the data_offset and we want to
mmap the tracefile only when needed, so we introduce a new function to
only compute this information when we are going to use a new packet.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
index 5cf8097ce709892580c49957cf4751f9bc2e753b..eec3350f3ba73b2c40c27c479943f3d80b4c093c 100644 (file)
--- a/formats/ctf/ctf.c
+++ b/formats/ctf/ctf.c
@@ -627,6 +627,107 @@ error:
        return ret;
 }
 
+/*
+ * One side-effect of this function is to unmap pos mmap base if one is
+ * mapped.
+ */
+static
+int find_data_offset(struct ctf_stream_pos *pos,
+               struct ctf_file_stream *file_stream,
+               struct packet_index *packet_index)
+{
+       uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len;
+       struct stat filestats;
+       size_t filesize;
+       int ret;
+
+       pos = &file_stream->pos;
+
+       ret = fstat(pos->fd, &filestats);
+       if (ret < 0)
+               return ret;
+       filesize = filestats.st_size;
+
+       /* Deal with empty files */
+       if (!filesize) {
+               return 0;
+       }
+
+begin:
+       if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) {
+               packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT;
+       }
+
+       if (pos->base_mma) {
+               /* unmap old base */
+               ret = munmap_align(pos->base_mma);
+               if (ret) {
+                       fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+                                       strerror(errno));
+                       return ret;
+               }
+               pos->base_mma = NULL;
+       }
+       /* map new base. Need mapping length from header. */
+       pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ,
+                       MAP_PRIVATE, pos->fd, pos->mmap_offset);
+       assert(pos->base_mma != MAP_FAILED);
+
+       pos->content_size = packet_map_len;
+       pos->packet_size = packet_map_len;
+       pos->offset = 0;        /* Position of the packet header */
+
+       /* update trace_packet_header and stream_packet_context */
+       if (pos->prot == PROT_READ && file_stream->parent.trace_packet_header) {
+               /* Read packet header */
+               ret = generic_rw(&pos->parent, &file_stream->parent.trace_packet_header->p);
+               if (ret) {
+                       if (ret == -EFAULT)
+                               goto retry;
+               }
+       }
+       if (pos->prot == PROT_READ && file_stream->parent.stream_packet_context) {
+               /* Read packet context */
+               ret = generic_rw(&pos->parent, &file_stream->parent.stream_packet_context->p);
+               if (ret) {
+                       if (ret == -EFAULT)
+                               goto retry;
+               }
+       }
+       packet_index->data_offset = pos->offset;
+
+       /* unmap old base */
+       ret = munmap_align(pos->base_mma);
+       if (ret) {
+               fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+                               strerror(errno));
+               return ret;
+       }
+       pos->base_mma = NULL;
+
+       return 0;
+
+       /* Retry with larger mapping */
+retry:
+       if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) {
+               /*
+                * Reached EOF, but still expecting header/context data.
+                */
+               fprintf(stderr, "[error] Reached end of file, but still expecting header or context fields.\n");
+               return -EFAULT;
+       }
+       /* Double the mapping len, and retry */
+       tmp_map_len = packet_map_len << 1;
+       if (tmp_map_len >> 1 != packet_map_len) {
+               /* Overflow */
+               fprintf(stderr, "[error] Packet mapping length overflow\n");
+               return -EFAULT;
+       }
+       packet_map_len = tmp_map_len;
+       goto begin;
+}
+
+
 int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor *trace,
                int fd, int open_flags)
 {
@@ -845,11 +946,17 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos, size_t index, int whence)
                                struct packet_index,
                                pos->cur_index);
                file_stream->parent.real_timestamp = packet_index->timestamp_begin;
-               pos->mmap_offset = packet_index->offset;
 
                /* Lookup context/packet size in index */
+               if (packet_index->data_offset == -1) {
+                       ret = find_data_offset(pos, file_stream, packet_index);
+                       if (ret < 0) {
+                               return;
+                       }
+               }
                pos->content_size = packet_index->content_size;
                pos->packet_size = packet_index->packet_size;
+               pos->mmap_offset = packet_index->offset;
                if (packet_index->data_offset < packet_index->content_size) {
                        pos->offset = 0;        /* will read headers */
                } else if (packet_index->data_offset == packet_index->content_size) {
@@ -1748,6 +1855,7 @@ int import_stream_packet_index(struct ctf_trace *td,
                index.timestamp_end = be64toh(ctf_index.timestamp_end);
                index.events_discarded = be64toh(ctf_index.events_discarded);
                index.events_discarded_len = 64;
+               index.data_offset = -1;
                stream_id = be64toh(ctf_index.stream_id);
 
                if (!first_packet) {