[Libguestfs] [PATCH v3 4/6] lib: qemu: Allow parallel qemu binaries to be used with cache conflicts.

Rename the cache files like ‘qemu.stat’ etc so they include the qemu binary "key" (ie. size and mtime) in the name. This allows a single user to use multiple qemu binaries in parallel without conflicts. --- lib/qemu.c | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/lib/qemu.c b/lib/qemu.c index 097d56929..1549bb33a 100644 --- a/lib/qemu.c +++ b/lib/qemu.c @@ -60,6 +60,7 @@ struct qemu_data { yajl_val qmp_schema_tree; /* qmp_schema parsed into a JSON tree */ }; +static char *cache_filename (guestfs_h *g, const char *cachedir, const struct stat *, const char *suffix); static int test_qemu_help (guestfs_h *g, struct qemu_data *data); static int read_cache_qemu_help (guestfs_h *g, struct qemu_data *data, const char *filename); static int write_cache_qemu_help (guestfs_h *g, const struct qemu_data *data, const char *filename); @@ -107,12 +108,12 @@ static const struct qemu_fields { }; #define NR_FIELDS (sizeof qemu_fields / sizeof qemu_fields[0]) -/* This is saved in the qemu.stat file, so if we decide to change the +/* This is saved in the qemu-*.stat file, so if we decide to change the * test_qemu memoization format/data in future, we should increment * this to discard any memoized data cached by previous versions of * libguestfs. */ -#define MEMO_GENERATION 2 +#define MEMO_GENERATION 3 /** * Test that the qemu binary (or wrapper) runs, and do C<qemu -help> @@ -147,7 +148,7 @@ guestfs_int_test_qemu (guestfs_h *g) data = safe_calloc (g, 1, sizeof *data); - stat_filename = safe_asprintf (g, "%s/qemu.stat", cachedir); + stat_filename = cache_filename (g, cachedir, &statbuf, "stat"); r = read_cache_qemu_stat (g, data, stat_filename); if (r == -1) goto error; @@ -163,7 +164,7 @@ guestfs_int_test_qemu (guestfs_h *g) for (i = 0; i < NR_FIELDS; ++i) { CLEANUP_FREE char *filename = - safe_asprintf (g, "%s/qemu.%s", cachedir, qemu_fields[i].name); + cache_filename (g, cachedir, &statbuf, qemu_fields[i].name); r = qemu_fields[i].read_cache (g, data, filename); if (r == -1) goto error; @@ -192,7 +193,7 @@ guestfs_int_test_qemu (guestfs_h *g) for (i = 0; i < NR_FIELDS; ++i) { CLEANUP_FREE char *filename = - safe_asprintf (g, "%s/qemu.%s", cachedir, qemu_fields[i].name); + cache_filename (g, cachedir, &statbuf, qemu_fields[i].name); if (qemu_fields[i].write_cache (g, data, filename) == -1) goto error; } @@ -218,6 +219,24 @@ guestfs_int_test_qemu (guestfs_h *g) return NULL; } +/** + * Generate the filenames, for the stat file and the other cache + * files. + * + * By including the size and mtime in the filename we also ensure that + * the same user can use multiple versions of qemu without conflicts. + */ +static char * +cache_filename (guestfs_h *g, const char *cachedir, + const struct stat *statbuf, const char *suffix) +{ + return safe_asprintf (g, "%s/qemu-%" PRIu64 "-%" PRIu64 ".%s", + cachedir, + (uint64_t) statbuf->st_size, + (uint64_t) statbuf->st_mtime, + suffix); +} + static int test_qemu_help (guestfs_h *g, struct qemu_data *data) { -- 2.13.2