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Stopped NBD writes from committing all-zero blocks to disc (tentative, needs

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further testing).
This commit is contained in:
Matthew Bloch
2012-05-18 13:24:35 +01:00
parent 0432fef8f5
commit ca53d6f270
5 changed files with 194 additions and 40 deletions
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27
ioutil.c
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@@ -47,12 +47,29 @@ char* build_allocation_map(int fd, off64_t size, int resolution)
if (ioctl(fd, FS_IOC_FIEMAP, fiemap) < -1)
return NULL;
for (i=0;i<fiemap->fm_mapped_extents;i++)
bit_set_range(
allocation_map,
fiemap->fm_extents[i].fe_logical / resolution,
fiemap->fm_extents[i].fe_length / resolution
for (i=0;i<fiemap->fm_mapped_extents;i++) {
int first_bit = fiemap->fm_extents[i].fe_logical / resolution;
int last_bit = (fiemap->fm_extents[i].fe_logical +
fiemap->fm_extents[i].fe_length + resolution - 1) /
resolution;
int run = last_bit - first_bit;
bit_set_range(allocation_map, first_bit, run);
}
for (i=0; i<16; i++) {
debug("map[%d] = %d%d%d%d%d%d%d%d",
i,
(allocation_map[i] & 1) == 1,
(allocation_map[i] & 2) == 2,
(allocation_map[i] & 4) == 4,
(allocation_map[i] & 8) == 8,
(allocation_map[i] & 16) == 16,
(allocation_map[i] & 32) == 32,
(allocation_map[i] & 64) == 64,
(allocation_map[i] & 128) == 128
);
}
free(fiemap);