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block/vpc: remove disabled code from get_sector_offset 

The code to check the bitmap for the allocation status of each sector
has been "disabled by reason" ever since the vpc driver existed.

The reason might be that we might end up reading sector by sector
in vpc_read if we really used it. This would be a performance desaster.

The current code would furthermore not work if the disabled parts get
reactivated since vpc_read and vpc_write only use get_sector_offset to
check the allocation status of the first sector of a read/write operation.
This might lead to sectors incorrectly treated as zero in vpc_read and
to sectors getting allocated twice in vpc_write.

Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1425379316-19639-6-git-send-email-pl@kamp.de
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Peter Lieven 2015-03-03 11:41:56 +01:00 committed by Max Reitz
parent 03671ded30
commit 304ee9174f
1 changed files with 0 additions and 32 deletions
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32
block/vpc.c
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@ -376,38 +376,6 @@ static inline int64_t get_sector_offset(BlockDriverState *bs,
bdrv_pwrite_sync(bs->file, bitmap_offset, bitmap, s->bitmap_size);
}
// printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n",
// sector_num, pagetable_index, pageentry_index,
// bitmap_offset, block_offset);
// disabled by reason
#if 0
#ifdef CACHE
if (bitmap_offset != s->last_bitmap)
{
lseek(s->fd, bitmap_offset, SEEK_SET);
s->last_bitmap = bitmap_offset;
// Scary! Bitmap is stored as big endian 32bit entries,
// while we used to look it up byte by byte
read(s->fd, s->pageentry_u8, 512);
for (i = 0; i < 128; i++)
be32_to_cpus(&s->pageentry_u32[i]);
}
if ((s->pageentry_u8[pageentry_index / 8] >> (pageentry_index % 8)) & 1)
return -1;
#else
lseek(s->fd, bitmap_offset + (pageentry_index / 8), SEEK_SET);
read(s->fd, &bitmap_entry, 1);
if ((bitmap_entry >> (pageentry_index % 8)) & 1)
return -1; // not allocated
#endif
#endif
return block_offset;
}