Fix tracecmd_read_at after file is fully read

When the file is completely read by tracecmd_read_data, the get_next_page
returns NULL, and no longer mmaps the file.

But tracecmd_read_at may be used after the file has been completely read.
This patch fixes this, and lets tracecmd_read_at work after the file
has been completely read.

Also converted some input_fd to handle->fd.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 43 insertions, 18 deletions

diff --git a/trace-input.c b/trace-input.c
index 299d7dc..38dd53d 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -45,6 +45,8 @@ struct tracecmd_handle {
 
 __thread struct tracecmd_handle *tracecmd_curr_thread_handle;
 
+static int init_cpu(struct tracecmd_handle *handle, int cpu);
+
 static int do_read(struct tracecmd_handle *handle, void *data, int size)
 {
         int tot = 0;
@@ -476,7 +478,7 @@ static int get_next_page(struct tracecmd_handle *handle, int cpu)
                 update_cpu_data_index(handle, cpu);
 
                 /* other parts of the code may expect the pointer to not move */
-                save_seek = lseek64(input_fd, 0, SEEK_CUR);
+                save_seek = lseek64(handle->fd, 0, SEEK_CUR);
 
                 ret = lseek64(handle->fd, handle->cpu_data[cpu].offset, SEEK_SET);
                 if (ret < 0)
@@ -486,7 +488,7 @@ static int get_next_page(struct tracecmd_handle *handle, int cpu)
                         return -1;
 
                 /* reset the file pointer back */
-                lseek64(input_fd, save_seek, SEEK_SET);
+                lseek64(handle->fd, save_seek, SEEK_SET);
 
                 return 0;
         }
@@ -500,7 +502,7 @@ static int get_next_page(struct tracecmd_handle *handle, int cpu)
         update_cpu_data_index(handle, cpu);
         
         handle->cpu_data[cpu].page = mmap(NULL, handle->page_size, PROT_READ, MAP_PRIVATE,
-                                  input_fd, handle->cpu_data[cpu].offset);
+                                  handle->fd, handle->cpu_data[cpu].offset);
         if (handle->cpu_data[cpu].page == MAP_FAILED)
                 return -1;
 
@@ -605,6 +607,8 @@ read_event(struct tracecmd_handle *handle, unsigned long long offset,
                 handle->cpu_data[cpu].index = 0;
 
         do {
+                /* Make sure peek returns new data */
+                handle->cpu_data[cpu].next = NULL;
                 record = tracecmd_read_data(handle, cpu);
         } while (record && (record->offset + record->record_size) <= offset);
 
@@ -633,18 +637,38 @@ find_and_read_event(struct tracecmd_handle *handle, unsigned long long offset,
         /* Move this cpu index to point to this offest */
         page_offset = offset & ~(handle->page_size - 1);
 
-        /*
-         * Set the cpu_data to point to the page in front.
-         */
-        page_offset -= handle->page_size;
+        if (handle->cpu_data[cpu].page) {
+                /*
+                 * If a page already exists, then we need to reset
+                 * it to point to the page with the data we want.
+                 * We update the pointers to point to the previous
+                 * page, and call get_next_page which will mmap
+                 * the next page after the pointer of the previous
+                 * page we want. Which ends up mapping the page we want.
+                 */
 
-        handle->cpu_data[cpu].offset = page_offset;
-        handle->cpu_data[cpu].size = (handle->cpu_data[cpu].file_offset +
-                                      handle->cpu_data[cpu].file_size) -
-                                       page_offset;
+                page_offset -= handle->page_size;
 
-        if (get_next_page(handle, cpu))
-                return NULL;
+                handle->cpu_data[cpu].offset = page_offset;
+                handle->cpu_data[cpu].size = (handle->cpu_data[cpu].file_offset +
+                                              handle->cpu_data[cpu].file_size) -
+                                                page_offset;
+
+                if (get_next_page(handle, cpu))
+                        return NULL;
+        } else {
+                /*
+                 * We need to map a new page. Just set it up the cpu_data
+                 * to the position we want.
+                 */
+                handle->cpu_data[cpu].offset = page_offset;
+                handle->cpu_data[cpu].size = (handle->cpu_data[cpu].file_offset +
+                                              handle->cpu_data[cpu].file_size) -
+                                                page_offset;
+
+                if (init_cpu(handle, cpu))
+                        return NULL;
+        }
 
         if (pcpu)
                 *pcpu = cpu;
@@ -824,17 +848,17 @@ static int init_read(struct tracecmd_handle *handle, int cpu)
                 return -1;
 
         /* other parts of the code may expect the pointer to not move */
-        save_seek = lseek64(input_fd, 0, SEEK_CUR);
+        save_seek = lseek64(handle->fd, 0, SEEK_CUR);
 
-        ret = lseek64(input_fd, (off64_t)handle->cpu_data[cpu].offset, SEEK_SET);
+        ret = lseek64(handle->fd, (off64_t)handle->cpu_data[cpu].offset, SEEK_SET);
         if (ret < 0)
                 return -1;
-        ret = read(input_fd, handle->cpu_data[cpu].page, handle->page_size);
+        ret = read(handle->fd, handle->cpu_data[cpu].page, handle->page_size);
         if (ret < 0)
                 return -1;
 
         /* reset the file pointer back */
-        lseek64(input_fd, save_seek, SEEK_SET);
+        lseek64(handle->fd, save_seek, SEEK_SET);
 
         return 0;
 }
@@ -850,9 +874,10 @@ static int init_cpu(struct tracecmd_handle *handle, int cpu)
                 return init_read(handle, cpu);
 
         handle->cpu_data[cpu].page = mmap(NULL, handle->page_size, PROT_READ,
-                                  MAP_PRIVATE, input_fd, handle->cpu_data[cpu].offset);
+                                  MAP_PRIVATE, handle->fd, handle->cpu_data[cpu].offset);
         if (handle->cpu_data[cpu].page == MAP_FAILED) {
                 /* fall back to just reading pages */
+                perror("mmap");
                 fprintf(stderr, "Can not mmap file, will read instead\n");
                 handle->read_page = 1;