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file-posix: Add image locking to perm operations

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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 <kwolf@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fam Zheng 2017-05-03 00:35:56 +08:00 committed by Kevin Wolf
parent e8c1094a0e
commit 244a566810
1 changed files with 275 additions and 1 deletions
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276
block/file-posix.c
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@ -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,