[Libguestfs] [nbdkit PATCH 1/2] blocksize: Refactor to per-handle constraints
Eric Blake
eblake at redhat.com
Wed Feb 23 15:45:32 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; the
change is merely the refactoring to get per-handle values, and
deferring the settling of defaults not specified during .config to now
be initialized during .prepare rather than .config_complete. The next
patch can then modify .block_size to actually honor the underlying
plugin constraints.
---
I wrote this patch by temporarily renaming the globals min_block and
so on, to let the compiler flag where we want to use the h->minblock
per-handle variant. If we want to leave the globals named slightly
differently for safety, let me know, and I can reinstate that.
---
filters/blocksize/blocksize.c | 162 +++++++++++++++++++++++-----------
1 file changed, 112 insertions(+), 50 deletions(-)
diff --git a/filters/blocksize/blocksize.c b/filters/blocksize/blocksize.c
index 38b57c1e..9a59a1aa 100644
--- a/filters/blocksize/blocksize.c
+++ b/filters/blocksize/blocksize.c
@@ -61,10 +61,18 @@ static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
*/
static char bounce[BLOCKSIZE_MIN_LIMIT];
+/* Globals set by .config */
static unsigned int minblock;
static unsigned int maxdata;
static unsigned int maxlen;
+/* Per-handle values set during .prepare */
+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)
{
@@ -114,28 +122,20 @@ blocksize_config_complete (nbdkit_next_config_complete *next,
return -1;
}
}
- else
- minblock = 1;
- if (maxdata) {
+ if (maxdata && minblock) {
if (maxdata & (minblock - 1)) {
nbdkit_error ("maxdata must be a multiple of %u", minblock);
return -1;
}
}
- else if (maxlen)
- maxdata = MIN (maxlen, 64 * 1024 * 1024);
- else
- maxdata = 64 * 1024 * 1024;
- if (maxlen) {
+ if (maxlen && minblock) {
if (maxlen & (minblock - 1)) {
nbdkit_error ("maxlen must be a multiple of %u", minblock);
return -1;
}
}
- else
- maxlen = -minblock;
return next (nxdata);
}
@@ -145,16 +145,66 @@ 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 = minblock;
+ h->maxdata = maxdata;
+ h->maxlen = maxlen;
+ return h;
+}
+
+static int
+blocksize_prepare (nbdkit_next *next, void *handle,
+ int readonly)
+{
+ struct blocksize_handle *h = handle;
+
+ if (h->minblock == 0)
+ h->minblock = 1;
+ if (h->maxdata == 0) {
+ if (h->maxlen)
+ h->maxdata = MIN (h->maxlen, 64 * 1024 * 1024);
+ else
+ h->maxdata = 64 * 1024 * 1024;
+ }
+ if (h->maxlen == 0)
+ h->maxlen = -h->minblock;
+
+ return 0;
+}
+
+
+static void
+blocksize_close (void *handle)
+{
+ free (handle);
+}
+
+
/* 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.
@@ -168,11 +218,13 @@ 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;
@@ -185,16 +237,17 @@ 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 +256,8 @@ 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 +268,7 @@ 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 +281,7 @@ 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 +294,14 @@ 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 +309,8 @@ 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 +321,10 @@ 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 +338,7 @@ 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 +349,18 @@ 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 +377,7 @@ 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 +388,7 @@ 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 +401,14 @@ 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 +416,8 @@ 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 +427,10 @@ 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 +451,22 @@ 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 +484,21 @@ 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 +514,9 @@ static struct nbdkit_filter filter = {
.config = blocksize_config,
.config_complete = blocksize_config_complete,
.config_help = blocksize_config_help,
+ .open = blocksize_open,
+ .prepare = blocksize_prepare,
+ .close = blocksize_close,
.get_size = blocksize_get_size,
.block_size = blocksize_block_size,
.pread = blocksize_pread,
--
2.35.1
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