| Message ID | 1425379316-19639-6-git-send-email-pl@kamp.de |
|---|---|
| State | New |
| Headers | show |
On 2015-03-03 at 05:41, Peter Lieven wrote: > 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> > --- > block/vpc.c | 32 -------------------------------- > 1 file changed, 32 deletions(-) Awww, that code nearly had its ten-year anniversary. Too bad it won't live to see it (I hope...). Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/vpc.c b/block/vpc.c index 226be02..43e768e 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -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; }
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> --- block/vpc.c | 32 -------------------------------- 1 file changed, 32 deletions(-)