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>
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sha1_file.c
70
sha1_file.c
@ -35,8 +35,6 @@ static size_t sz_fmt(size_t s) { return s; }
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const unsigned char null_sha1[20];
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static unsigned int sha1_file_open_flag = O_NOATIME;
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const signed char hexval_table[256] = {
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-1, -1, -1, -1, -1, -1, -1, -1, /* 00-07 */
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-1, -1, -1, -1, -1, -1, -1, -1, /* 08-0f */
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@ -997,38 +995,58 @@ int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long siz
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return hashcmp(sha1, real_sha1) ? -1 : 0;
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}
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static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
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static int git_open_noatime(const char *name)
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{
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struct stat st;
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void *map;
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int fd;
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char *filename = find_sha1_file(sha1, &st);
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static int sha1_file_open_flag = O_NOATIME;
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int fd = open(name, O_RDONLY | sha1_file_open_flag);
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if (!filename) {
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return NULL;
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}
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fd = open(filename, O_RDONLY | sha1_file_open_flag);
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if (fd < 0) {
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/* See if it works without O_NOATIME */
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switch (sha1_file_open_flag) {
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default:
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fd = open(filename, O_RDONLY);
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/* Might the failure be due to O_NOATIME? */
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if (fd < 0 && errno != ENOENT && sha1_file_open_flag) {
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fd = open(name, O_RDONLY);
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if (fd >= 0)
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break;
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/* Fallthrough */
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case 0:
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return NULL;
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}
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/* If it failed once, it will probably fail again.
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* Stop using O_NOATIME
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*/
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sha1_file_open_flag = 0;
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}
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return fd;
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}
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static int open_sha1_file(const unsigned char *sha1)
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{
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int fd;
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char *name = sha1_file_name(sha1);
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struct alternate_object_database *alt;
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fd = git_open_noatime(name);
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if (fd >= 0)
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return fd;
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prepare_alt_odb();
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errno = ENOENT;
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for (alt = alt_odb_list; alt; alt = alt->next) {
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name = alt->name;
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fill_sha1_path(name, sha1);
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fd = git_open_noatime(alt->base);
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if (fd >= 0)
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return fd;
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}
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return -1;
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}
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static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
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{
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void *map;
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int fd;
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fd = open_sha1_file(sha1);
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map = NULL;
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if (fd >= 0) {
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struct stat st;
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if (!fstat(fd, &st)) {
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*size = xsize_t(st.st_size);
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map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
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}
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close(fd);
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}
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return map;
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}
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