Make loose object file reading more careful
We used to do 'stat()+open()+mmap()+close()' to read the loose object
file data, which does work fine, but has a couple of problems:
- it unnecessarily walks the filename twice (at 'stat()' time and then
again to open it)
- NFS generally has open-close consistency guarantees, which means that
the initial 'stat()' was technically done outside of the normal
consistency rules.
So change it to do 'open()+fstat()+mmap()+close()' instead, which avoids
both these issues.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sha1_file.c b/sha1_file.c
index 8d48a23..71a25e7 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -35,8 +35,6 @@
const unsigned char null_sha1[20];
-static unsigned int sha1_file_open_flag = O_NOATIME;
-
const signed char hexval_table[256] = {
-1, -1, -1, -1, -1, -1, -1, -1, /* 00-07 */
-1, -1, -1, -1, -1, -1, -1, -1, /* 08-0f */
@@ -997,38 +995,58 @@
return hashcmp(sha1, real_sha1) ? -1 : 0;
}
+static int git_open_noatime(const char *name)
+{
+ static int sha1_file_open_flag = O_NOATIME;
+ int fd = open(name, O_RDONLY | sha1_file_open_flag);
+
+ /* Might the failure be due to O_NOATIME? */
+ if (fd < 0 && errno != ENOENT && sha1_file_open_flag) {
+ fd = open(name, O_RDONLY);
+ if (fd >= 0)
+ sha1_file_open_flag = 0;
+ }
+ return fd;
+}
+
+static int open_sha1_file(const unsigned char *sha1)
+{
+ int fd;
+ char *name = sha1_file_name(sha1);
+ struct alternate_object_database *alt;
+
+ fd = git_open_noatime(name);
+ if (fd >= 0)
+ return fd;
+
+ prepare_alt_odb();
+ errno = ENOENT;
+ for (alt = alt_odb_list; alt; alt = alt->next) {
+ name = alt->name;
+ fill_sha1_path(name, sha1);
+ fd = git_open_noatime(alt->base);
+ if (fd >= 0)
+ return fd;
+ }
+ return -1;
+}
+
static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
{
- struct stat st;
void *map;
int fd;
- char *filename = find_sha1_file(sha1, &st);
- if (!filename) {
- return NULL;
- }
+ fd = open_sha1_file(sha1);
+ map = NULL;
+ if (fd >= 0) {
+ struct stat st;
- fd = open(filename, O_RDONLY | sha1_file_open_flag);
- if (fd < 0) {
- /* See if it works without O_NOATIME */
- switch (sha1_file_open_flag) {
- default:
- fd = open(filename, O_RDONLY);
- if (fd >= 0)
- break;
- /* Fallthrough */
- case 0:
- return NULL;
+ if (!fstat(fd, &st)) {
+ *size = xsize_t(st.st_size);
+ map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
}
-
- /* If it failed once, it will probably fail again.
- * Stop using O_NOATIME
- */
- sha1_file_open_flag = 0;
+ close(fd);
}
- *size = xsize_t(st.st_size);
- map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
- close(fd);
return map;
}
