From 244a5668106297378391b768e7288eb157616f64 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Wed, 3 May 2017 00:35:56 +0800 Subject: [PATCH] file-posix: Add image locking to perm operations This extends the permission bits of op blocker API to external using Linux OFD locks. Each permission in @perm and @shared_perm is represented by a locked byte in the image file. Requesting a permission in @perm is translated to a shared lock of the corresponding byte; rejecting to share the same permission is translated to a shared lock of a separate byte. With that, we use 2x number of bytes of distinct permission types. virtlockd in libvirt locks the first byte, so we do locking from a higher offset. Suggested-by: Kevin Wolf Signed-off-by: Fam Zheng Signed-off-by: Kevin Wolf --- block/file-posix.c | 276 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 275 insertions(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index d13e99c43f..a09055b700 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -129,12 +129,23 @@ do { \ #define MAX_BLOCKSIZE 4096 +/* Posix file locking bytes. Libvirt takes byte 0, we start from higher bytes, + * leaving a few more bytes for its future use. */ +#define RAW_LOCK_PERM_BASE 100 +#define RAW_LOCK_SHARED_BASE 200 + typedef struct BDRVRawState { int fd; + int lock_fd; + bool use_lock; int type; int open_flags; size_t buf_align; + /* The current permissions. */ + uint64_t perm; + uint64_t shared_perm; + #ifdef CONFIG_XFS bool is_xfs:1; #endif @@ -411,6 +422,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, BlockdevAioOptions aio, aio_default; int fd, ret; struct stat st; + OnOffAuto locking; opts = qemu_opts_create(&raw_runtime_opts, NULL, 0, &error_abort); qemu_opts_absorb_qdict(opts, options, &local_err); @@ -440,6 +452,37 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } s->use_linux_aio = (aio == BLOCKDEV_AIO_OPTIONS_NATIVE); + locking = qapi_enum_parse(OnOffAuto_lookup, qemu_opt_get(opts, "locking"), + ON_OFF_AUTO__MAX, ON_OFF_AUTO_AUTO, &local_err); + if (local_err) { + error_propagate(errp, local_err); + ret = -EINVAL; + goto fail; + } + switch (locking) { + case ON_OFF_AUTO_ON: + s->use_lock = true; +#ifndef F_OFD_SETLK + fprintf(stderr, + "File lock requested but OFD locking syscall is unavailable, " + "falling back to POSIX file locks.\n" + "Due to the implementation, locks can be lost unexpectedly.\n"); +#endif + break; + case ON_OFF_AUTO_OFF: + s->use_lock = false; + break; + case ON_OFF_AUTO_AUTO: +#ifdef F_OFD_SETLK + s->use_lock = true; +#else + s->use_lock = false; +#endif + break; + default: + abort(); + } + s->open_flags = open_flags; raw_parse_flags(bdrv_flags, &s->open_flags); @@ -455,6 +498,21 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } s->fd = fd; + s->lock_fd = -1; + if (s->use_lock) { + fd = qemu_open(filename, s->open_flags); + if (fd < 0) { + ret = -errno; + error_setg_errno(errp, errno, "Could not open '%s' for locking", + filename); + qemu_close(s->fd); + goto fail; + } + s->lock_fd = fd; + } + s->perm = 0; + s->shared_perm = BLK_PERM_ALL; + #ifdef CONFIG_LINUX_AIO /* Currently Linux does AIO only for files opened with O_DIRECT */ if (s->use_linux_aio && !(s->open_flags & O_DIRECT)) { @@ -542,6 +600,161 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags, return raw_open_common(bs, options, flags, 0, errp); } +typedef enum { + RAW_PL_PREPARE, + RAW_PL_COMMIT, + RAW_PL_ABORT, +} RawPermLockOp; + +#define PERM_FOREACH(i) \ + for ((i) = 0; (1ULL << (i)) <= BLK_PERM_ALL; i++) + +/* Lock bytes indicated by @perm_lock_bits and @shared_perm_lock_bits in the + * file; if @unlock == true, also unlock the unneeded bytes. + * @shared_perm_lock_bits is the mask of all permissions that are NOT shared. + */ +static int raw_apply_lock_bytes(BDRVRawState *s, + uint64_t perm_lock_bits, + uint64_t shared_perm_lock_bits, + bool unlock, Error **errp) +{ + int ret; + int i; + + PERM_FOREACH(i) { + int off = RAW_LOCK_PERM_BASE + i; + if (perm_lock_bits & (1ULL << i)) { + ret = qemu_lock_fd(s->lock_fd, off, 1, false); + if (ret) { + error_setg(errp, "Failed to lock byte %d", off); + return ret; + } + } else if (unlock) { + ret = qemu_unlock_fd(s->lock_fd, off, 1); + if (ret) { + error_setg(errp, "Failed to unlock byte %d", off); + return ret; + } + } + } + PERM_FOREACH(i) { + int off = RAW_LOCK_SHARED_BASE + i; + if (shared_perm_lock_bits & (1ULL << i)) { + ret = qemu_lock_fd(s->lock_fd, off, 1, false); + if (ret) { + error_setg(errp, "Failed to lock byte %d", off); + return ret; + } + } else if (unlock) { + ret = qemu_unlock_fd(s->lock_fd, off, 1); + if (ret) { + error_setg(errp, "Failed to unlock byte %d", off); + return ret; + } + } + } + return 0; +} + +/* Check "unshared" bytes implied by @perm and ~@shared_perm in the file. */ +static int raw_check_lock_bytes(BDRVRawState *s, + uint64_t perm, uint64_t shared_perm, + Error **errp) +{ + int ret; + int i; + + PERM_FOREACH(i) { + int off = RAW_LOCK_SHARED_BASE + i; + uint64_t p = 1ULL << i; + if (perm & p) { + ret = qemu_lock_fd_test(s->lock_fd, off, 1, true); + if (ret) { + char *perm_name = bdrv_perm_names(p); + error_setg(errp, + "Failed to get \"%s\" lock", + perm_name); + g_free(perm_name); + error_append_hint(errp, + "Is another process using the image?\n"); + return ret; + } + } + } + PERM_FOREACH(i) { + int off = RAW_LOCK_PERM_BASE + i; + uint64_t p = 1ULL << i; + if (!(shared_perm & p)) { + ret = qemu_lock_fd_test(s->lock_fd, off, 1, true); + if (ret) { + char *perm_name = bdrv_perm_names(p); + error_setg(errp, + "Failed to get shared \"%s\" lock", + perm_name); + g_free(perm_name); + error_append_hint(errp, + "Is another process using the image?\n"); + return ret; + } + } + } + return 0; +} + +static int raw_handle_perm_lock(BlockDriverState *bs, + RawPermLockOp op, + uint64_t new_perm, uint64_t new_shared, + Error **errp) +{ + BDRVRawState *s = bs->opaque; + int ret = 0; + Error *local_err = NULL; + + if (!s->use_lock) { + return 0; + } + + if (bdrv_get_flags(bs) & BDRV_O_INACTIVE) { + return 0; + } + + assert(s->lock_fd > 0); + + switch (op) { + case RAW_PL_PREPARE: + ret = raw_apply_lock_bytes(s, s->perm | new_perm, + ~s->shared_perm | ~new_shared, + false, errp); + if (!ret) { + ret = raw_check_lock_bytes(s, new_perm, new_shared, errp); + if (!ret) { + return 0; + } + } + op = RAW_PL_ABORT; + /* fall through to unlock bytes. */ + case RAW_PL_ABORT: + raw_apply_lock_bytes(s, s->perm, ~s->shared_perm, true, &local_err); + if (local_err) { + /* Theoretically the above call only unlocks bytes and it cannot + * fail. Something weird happened, report it. + */ + error_report_err(local_err); + } + break; + case RAW_PL_COMMIT: + raw_apply_lock_bytes(s, new_perm, ~new_shared, true, &local_err); + if (local_err) { + /* Theoretically the above call only unlocks bytes and it cannot + * fail. Something weird happened, report it. + */ + error_report_err(local_err); + } + break; + } + return ret; +} + static int raw_reopen_prepare(BDRVReopenState *state, BlockReopenQueue *queue, Error **errp) { @@ -1410,6 +1623,10 @@ static void raw_close(BlockDriverState *bs) qemu_close(s->fd); s->fd = -1; } + if (s->lock_fd >= 0) { + qemu_close(s->lock_fd); + s->lock_fd = -1; + } } static int raw_truncate(BlockDriverState *bs, int64_t offset, Error **errp) @@ -1954,6 +2171,54 @@ static QemuOptsList raw_create_opts = { } }; +static int raw_check_perm(BlockDriverState *bs, uint64_t perm, uint64_t shared, + Error **errp) +{ + return raw_handle_perm_lock(bs, RAW_PL_PREPARE, perm, shared, errp); +} + +static void raw_set_perm(BlockDriverState *bs, uint64_t perm, uint64_t shared) +{ + BDRVRawState *s = bs->opaque; + raw_handle_perm_lock(bs, RAW_PL_COMMIT, perm, shared, NULL); + s->perm = perm; + s->shared_perm = shared; +} + +static void raw_abort_perm_update(BlockDriverState *bs) +{ + raw_handle_perm_lock(bs, RAW_PL_ABORT, 0, 0, NULL); +} + +static int raw_inactivate(BlockDriverState *bs) +{ + int ret; + uint64_t perm = 0; + uint64_t shared = BLK_PERM_ALL; + + ret = raw_handle_perm_lock(bs, RAW_PL_PREPARE, perm, shared, NULL); + if (ret) { + return ret; + } + raw_handle_perm_lock(bs, RAW_PL_COMMIT, perm, shared, NULL); + return 0; +} + + +static void raw_invalidate_cache(BlockDriverState *bs, Error **errp) +{ + BDRVRawState *s = bs->opaque; + int ret; + + assert(!(bdrv_get_flags(bs) & BDRV_O_INACTIVE)); + ret = raw_handle_perm_lock(bs, RAW_PL_PREPARE, s->perm, s->shared_perm, + errp); + if (ret) { + return; + } + raw_handle_perm_lock(bs, RAW_PL_COMMIT, s->perm, s->shared_perm, NULL); +} + BlockDriver bdrv_file = { .format_name = "file", .protocol_name = "file", @@ -1984,7 +2249,11 @@ BlockDriver bdrv_file = { .bdrv_get_info = raw_get_info, .bdrv_get_allocated_file_size = raw_get_allocated_file_size, - + .bdrv_inactivate = raw_inactivate, + .bdrv_invalidate_cache = raw_invalidate_cache, + .bdrv_check_perm = raw_check_perm, + .bdrv_set_perm = raw_set_perm, + .bdrv_abort_perm_update = raw_abort_perm_update, .create_opts = &raw_create_opts, }; @@ -2443,6 +2712,11 @@ static BlockDriver bdrv_host_device = { .bdrv_get_info = raw_get_info, .bdrv_get_allocated_file_size = raw_get_allocated_file_size, + .bdrv_inactivate = raw_inactivate, + .bdrv_invalidate_cache = raw_invalidate_cache, + .bdrv_check_perm = raw_check_perm, + .bdrv_set_perm = raw_set_perm, + .bdrv_abort_perm_update = raw_abort_perm_update, .bdrv_probe_blocksizes = hdev_probe_blocksizes, .bdrv_probe_geometry = hdev_probe_geometry,