[Libguestfs] [nbdkit PATCH v2 1/3] blocksize: Refactor to per-handle constraints
Eric Blake
eblake at redhat.com
Thu Feb 24 15:36:47 UTC 2022
An upcoming patch wants to make the blocksize filter more responsive
to the actual .block_size limits from the underlying plugin. But
those limits can differ per export (for example, qemu can export
multiple images, where one backed by a file has minblock 1, but
another backed by encryption has minblock 512).
To do that, we need to track block size constraints per handle, rather
than globally. At this point, no functional change is intended other
than three new debug lines; the change is merely the refactoring to
get per-handle values set in .open (mostly mechanical renaming to
easily distinguish .config defaults from the per-handle values, even
though for now every handle has the same values). The next patches
can then defer the defaulting of unspecified values to .prepare, where
it can also take into account .block_size constraints.
---
filters/blocksize/blocksize.c | 167 ++++++++++++++++++++++------------
1 file changed, 107 insertions(+), 60 deletions(-)
diff --git a/filters/blocksize/blocksize.c b/filters/blocksize/blocksize.c
index 38b57c1e..e0420409 100644
--- a/filters/blocksize/blocksize.c
+++ b/filters/blocksize/blocksize.c
@@ -61,9 +61,17 @@ static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
*/
static char bounce[BLOCKSIZE_MIN_LIMIT];
-static unsigned int minblock;
-static unsigned int maxdata;
-static unsigned int maxlen;
+/* Globals set by .config */
+static unsigned int config_minblock;
+static unsigned int config_maxdata;
+static unsigned int config_maxlen;
+
+/* Per-handle values set during .open */
+struct blocksize_handle {
+ uint32_t minblock;
+ uint32_t maxdata;
+ uint32_t maxlen;
+};
static int
blocksize_parse (const char *name, const char *s, unsigned int *v)
@@ -91,11 +99,11 @@ blocksize_config (nbdkit_next_config *next, nbdkit_backend *nxdata,
{
if (strcmp (key, "minblock") == 0)
- return blocksize_parse (key, value, &minblock);
+ return blocksize_parse (key, value, &config_minblock);
if (strcmp (key, "maxdata") == 0)
- return blocksize_parse (key, value, &maxdata);
+ return blocksize_parse (key, value, &config_maxdata);
if (strcmp (key, "maxlen") == 0)
- return blocksize_parse (key, value, &maxlen);
+ return blocksize_parse (key, value, &config_maxlen);
return next (nxdata, key, value);
}
@@ -104,39 +112,41 @@ static int
blocksize_config_complete (nbdkit_next_config_complete *next,
nbdkit_backend *nxdata)
{
- if (minblock) {
- if (!is_power_of_2 (minblock)) {
+ if (config_minblock) {
+ if (!is_power_of_2 (config_minblock)) {
nbdkit_error ("minblock must be a power of 2");
return -1;
}
- if (minblock > BLOCKSIZE_MIN_LIMIT) {
+ if (config_minblock > BLOCKSIZE_MIN_LIMIT) {
nbdkit_error ("minblock must not exceed %u", BLOCKSIZE_MIN_LIMIT);
return -1;
}
}
else
- minblock = 1;
+ config_minblock = 1;
- if (maxdata) {
- if (maxdata & (minblock - 1)) {
- nbdkit_error ("maxdata must be a multiple of %u", minblock);
+ if (config_maxdata) {
+ if (config_maxdata & (config_minblock - 1)) {
+ nbdkit_error ("maxdata must be a multiple of %u", config_minblock);
return -1;
}
}
- else if (maxlen)
- maxdata = MIN (maxlen, 64 * 1024 * 1024);
+ else if (config_maxlen)
+ config_maxdata = MIN (config_maxlen, 64 * 1024 * 1024);
else
- maxdata = 64 * 1024 * 1024;
+ config_maxdata = 64 * 1024 * 1024;
- if (maxlen) {
- if (maxlen & (minblock - 1)) {
- nbdkit_error ("maxlen must be a multiple of %u", minblock);
+ if (config_maxlen) {
+ if (config_maxlen & (config_minblock - 1)) {
+ nbdkit_error ("maxlen must be a multiple of %u", config_minblock);
return -1;
}
}
else
- maxlen = -minblock;
+ config_maxlen = -config_minblock;
+ nbdkit_debug ("configured values minblock=%u maxdata=%u maxlen=%u",
+ config_minblock, config_maxdata, config_maxlen);
return next (nxdata);
}
@@ -145,16 +155,40 @@ blocksize_config_complete (nbdkit_next_config_complete *next,
"maxdata=<SIZE> Maximum size for read/write (default 64M).\n" \
"maxlen=<SIZE> Maximum size for trim/zero (default 4G-minblock)."
+static void *
+blocksize_open (nbdkit_next_open *next, nbdkit_context *nxdata,
+ int readonly, const char *exportname, int is_tls)
+{
+ struct blocksize_handle *h;
+
+ if (next (nxdata, readonly, exportname) == -1)
+ return NULL;
+
+ h = malloc (sizeof *h);
+ if (h == NULL) {
+ nbdkit_error ("malloc: %m");
+ return NULL;
+ }
+
+ h->minblock = config_minblock;
+ h->maxdata = config_maxdata;
+ h->maxlen = config_maxlen;
+ nbdkit_debug ("handle values minblock=%u maxdata=%u maxlen=%u",
+ h->minblock, h->maxdata, h->maxlen);
+ return h;
+}
+
/* Round size down to avoid issues at end of file. */
static int64_t
blocksize_get_size (nbdkit_next *next,
void *handle)
{
+ struct blocksize_handle *h = handle;
int64_t size = next->get_size (next);
if (size == -1)
return -1;
- return ROUND_DOWN (size, minblock);
+ return ROUND_DOWN (size, h->minblock);
}
/* Block size constraints.
@@ -168,15 +202,19 @@ static int
blocksize_block_size (nbdkit_next *next, void *handle,
uint32_t *minimum, uint32_t *preferred, uint32_t *maximum)
{
+ struct blocksize_handle *h = handle;
+
if (next->block_size (next, minimum, preferred, maximum) == -1)
return -1;
if (*preferred == 0)
- *preferred = MAX (4096, minblock);
+ *preferred = MAX (4096, h->minblock);
*minimum = 1;
*maximum = 0xffffffff;
+ nbdkit_debug ("advertising min=%" PRIu32 " pref=%" PRIu32 " max=%" PRIu32,
+ *minimum, *preferred, *maximum);
return 0;
}
@@ -185,16 +223,17 @@ blocksize_pread (nbdkit_next *next,
void *handle, void *b, uint32_t count, uint64_t offs,
uint32_t flags, int *err)
{
+ struct blocksize_handle *h = handle;
char *buf = b;
uint32_t keep;
uint32_t drop;
/* Unaligned head */
- if (offs & (minblock - 1)) {
+ if (offs & (h->minblock - 1)) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- drop = offs & (minblock - 1);
- keep = MIN (minblock - drop, count);
- if (next->pread (next, bounce, minblock, offs - drop, flags, err) == -1)
+ drop = offs & (h->minblock - 1);
+ keep = MIN (h->minblock - drop, count);
+ if (next->pread (next, bounce, h->minblock, offs - drop, flags, err) == -1)
return -1;
memcpy (buf, bounce + drop, keep);
buf += keep;
@@ -203,8 +242,8 @@ blocksize_pread (nbdkit_next *next,
}
/* Aligned body */
- while (count >= minblock) {
- keep = MIN (maxdata, ROUND_DOWN (count, minblock));
+ while (count >= h->minblock) {
+ keep = MIN (h->maxdata, ROUND_DOWN (count, h->minblock));
if (next->pread (next, buf, keep, offs, flags, err) == -1)
return -1;
buf += keep;
@@ -215,7 +254,7 @@ blocksize_pread (nbdkit_next *next,
/* Unaligned tail */
if (count) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- if (next->pread (next, bounce, minblock, offs, flags, err) == -1)
+ if (next->pread (next, bounce, h->minblock, offs, flags, err) == -1)
return -1;
memcpy (buf, bounce, count);
}
@@ -228,6 +267,7 @@ blocksize_pwrite (nbdkit_next *next,
void *handle, const void *b, uint32_t count, uint64_t offs,
uint32_t flags, int *err)
{
+ struct blocksize_handle *h = handle;
const char *buf = b;
uint32_t keep;
uint32_t drop;
@@ -240,14 +280,14 @@ blocksize_pwrite (nbdkit_next *next,
}
/* Unaligned head */
- if (offs & (minblock - 1)) {
+ if (offs & (h->minblock - 1)) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- drop = offs & (minblock - 1);
- keep = MIN (minblock - drop, count);
- if (next->pread (next, bounce, minblock, offs - drop, 0, err) == -1)
+ drop = offs & (h->minblock - 1);
+ keep = MIN (h->minblock - drop, count);
+ if (next->pread (next, bounce, h->minblock, offs - drop, 0, err) == -1)
return -1;
memcpy (bounce + drop, buf, keep);
- if (next->pwrite (next, bounce, minblock, offs - drop, flags, err) == -1)
+ if (next->pwrite (next, bounce, h->minblock, offs - drop, flags, err) == -1)
return -1;
buf += keep;
offs += keep;
@@ -255,8 +295,8 @@ blocksize_pwrite (nbdkit_next *next,
}
/* Aligned body */
- while (count >= minblock) {
- keep = MIN (maxdata, ROUND_DOWN (count, minblock));
+ while (count >= h->minblock) {
+ keep = MIN (h->maxdata, ROUND_DOWN (count, h->minblock));
if (next->pwrite (next, buf, keep, offs, flags, err) == -1)
return -1;
buf += keep;
@@ -267,10 +307,10 @@ blocksize_pwrite (nbdkit_next *next,
/* Unaligned tail */
if (count) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- if (next->pread (next, bounce, minblock, offs, 0, err) == -1)
+ if (next->pread (next, bounce, h->minblock, offs, 0, err) == -1)
return -1;
memcpy (bounce, buf, count);
- if (next->pwrite (next, bounce, minblock, offs, flags, err) == -1)
+ if (next->pwrite (next, bounce, h->minblock, offs, flags, err) == -1)
return -1;
}
@@ -284,6 +324,7 @@ blocksize_trim (nbdkit_next *next,
void *handle, uint32_t count, uint64_t offs, uint32_t flags,
int *err)
{
+ struct blocksize_handle *h = handle;
uint32_t keep;
bool need_flush = false;
@@ -294,18 +335,18 @@ blocksize_trim (nbdkit_next *next,
}
/* Ignore unaligned head */
- if (offs & (minblock - 1)) {
- keep = MIN (minblock - (offs & (minblock - 1)), count);
+ if (offs & (h->minblock - 1)) {
+ keep = MIN (h->minblock - (offs & (h->minblock - 1)), count);
offs += keep;
count -= keep;
}
/* Ignore unaligned tail */
- count = ROUND_DOWN (count, minblock);
+ count = ROUND_DOWN (count, h->minblock);
/* Aligned body */
while (count) {
- keep = MIN (maxlen, count);
+ keep = MIN (h->maxlen, count);
if (next->trim (next, keep, offs, flags, err) == -1)
return -1;
offs += keep;
@@ -322,6 +363,7 @@ blocksize_zero (nbdkit_next *next,
void *handle, uint32_t count, uint64_t offs, uint32_t flags,
int *err)
{
+ struct blocksize_handle *h = handle;
uint32_t keep;
uint32_t drop;
bool need_flush = false;
@@ -332,7 +374,7 @@ blocksize_zero (nbdkit_next *next,
* calls; it's easier to just declare that anything that can't be
* done in one call to the plugin is not fast.
*/
- if ((offs | count) & (minblock - 1) || count > maxlen) {
+ if ((offs | count) & (h->minblock - 1) || count > h->maxlen) {
*err = ENOTSUP;
return -1;
}
@@ -345,14 +387,14 @@ blocksize_zero (nbdkit_next *next,
}
/* Unaligned head */
- if (offs & (minblock - 1)) {
+ if (offs & (h->minblock - 1)) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- drop = offs & (minblock - 1);
- keep = MIN (minblock - drop, count);
- if (next->pread (next, bounce, minblock, offs - drop, 0, err) == -1)
+ drop = offs & (h->minblock - 1);
+ keep = MIN (h->minblock - drop, count);
+ if (next->pread (next, bounce, h->minblock, offs - drop, 0, err) == -1)
return -1;
memset (bounce + drop, 0, keep);
- if (next->pwrite (next, bounce, minblock, offs - drop,
+ if (next->pwrite (next, bounce, h->minblock, offs - drop,
flags & ~NBDKIT_FLAG_MAY_TRIM, err) == -1)
return -1;
offs += keep;
@@ -360,8 +402,8 @@ blocksize_zero (nbdkit_next *next,
}
/* Aligned body */
- while (count >= minblock) {
- keep = MIN (maxlen, ROUND_DOWN (count, minblock));
+ while (count >= h->minblock) {
+ keep = MIN (h->maxlen, ROUND_DOWN (count, h->minblock));
if (next->zero (next, keep, offs, flags, err) == -1)
return -1;
offs += keep;
@@ -371,10 +413,10 @@ blocksize_zero (nbdkit_next *next,
/* Unaligned tail */
if (count) {
ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
- if (next->pread (next, bounce, minblock, offs, 0, err) == -1)
+ if (next->pread (next, bounce, h->minblock, offs, 0, err) == -1)
return -1;
memset (bounce, 0, count);
- if (next->pwrite (next, bounce, minblock, offs,
+ if (next->pwrite (next, bounce, h->minblock, offs,
flags & ~NBDKIT_FLAG_MAY_TRIM, err) == -1)
return -1;
}
@@ -395,20 +437,22 @@ blocksize_extents (nbdkit_next *next,
* fine to return less than the full count as long as we're making
* progress.
*/
+ struct blocksize_handle *h = handle;
CLEANUP_EXTENTS_FREE struct nbdkit_extents *extents2 = NULL;
size_t i;
struct nbdkit_extent e;
- extents2 = nbdkit_extents_new (ROUND_DOWN (offset, minblock),
- ROUND_UP (offset + count, minblock));
+ extents2 = nbdkit_extents_new (ROUND_DOWN (offset, h->minblock),
+ ROUND_UP (offset + count, h->minblock));
if (extents2 == NULL) {
*err = errno;
return -1;
}
- if (nbdkit_extents_aligned (next, MIN (ROUND_UP (count, minblock), maxlen),
- ROUND_DOWN (offset, minblock), flags, minblock,
- extents2, err) == -1)
+ if (nbdkit_extents_aligned (next, MIN (ROUND_UP (count, h->minblock),
+ h->maxlen),
+ ROUND_DOWN (offset, h->minblock), flags,
+ h->minblock, extents2, err) == -1)
return -1;
for (i = 0; i < nbdkit_extents_count (extents2); ++i) {
@@ -426,20 +470,21 @@ blocksize_cache (nbdkit_next *next,
void *handle, uint32_t count, uint64_t offs, uint32_t flags,
int *err)
{
+ struct blocksize_handle *h = handle;
uint32_t limit;
uint64_t remaining = count; /* Rounding out could exceed 32 bits */
/* Unaligned head */
- limit = offs & (minblock - 1);
+ limit = offs & (h->minblock - 1);
remaining += limit;
offs -= limit;
/* Unaligned tail */
- remaining = ROUND_UP (remaining, minblock);
+ remaining = ROUND_UP (remaining, h->minblock);
/* Aligned body */
while (remaining) {
- limit = MIN (maxdata, remaining);
+ limit = MIN (h->maxdata, remaining);
if (next->cache (next, limit, offs, flags, err) == -1)
return -1;
offs += limit;
@@ -455,6 +500,8 @@ static struct nbdkit_filter filter = {
.config = blocksize_config,
.config_complete = blocksize_config_complete,
.config_help = blocksize_config_help,
+ .open = blocksize_open,
+ .close = free,
.get_size = blocksize_get_size,
.block_size = blocksize_block_size,
.pread = blocksize_pread,
--
2.35.1
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