File 0157-block-vpc-remove-disabled-code-from.patch of Package qemu.7445

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File 0157-block-vpc-remove-disabled-code-from.patch of Package qemu.7445

From f1dd687872cf2997e0e92ff845f83a7f3d248f87 Mon Sep 17 00:00:00 2001
From: Peter Lieven <pl@kamp.de>
Date: Tue, 3 Mar 2015 11:41:56 +0100
Subject: [PATCH] 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>
(cherry picked from commit 304ee9174f4761d3f4da611352a815ab27baba06)
[CYL: BNC#886378]
Signed-off-by: Chunyan Liu <cyliu@suse.com>
---
 block/vpc.c | 32 --------------------------------
 1 file changed, 32 deletions(-)

diff --git a/block/vpc.c b/block/vpc.c
index 1054787360..844cbcab72 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -379,38 +379,6 @@ 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;
 }

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