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From 69fe324e32aad7e1afc6ad14021a6a08ad52646c Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Sat, 13 Jun 2015 16:22:27 +0200
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Subject: [PATCH 33/42] block: Respect underlying file's EOF
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Message-id: <1434212556-3927-34-git-send-email-mreitz@redhat.com>
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Patchwork-id: 66052
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O-Subject: [RHEL-7.2 qemu-kvm PATCH 33/42] block: Respect underlying file's EOF
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Bugzilla: 1129893
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1129893
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When falling through to the underlying file in
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bdrv_co_get_block_status(), if it returns that the query offset is
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beyond the file end (by setting *pnum to 0), return the range to be
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zero and do not let the number of sectors for which information could be
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obtained be overwritten.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 59c9a95fd29cfb3296ee58e8a446df251d14a459)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block.c | 15 +++++++++++++--
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 1 file changed, 13 insertions(+), 2 deletions(-)
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diff --git a/block.c b/block.c
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index 22ab762..fa6e192 100644
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--- a/block.c
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+++ b/block.c
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@@ -3797,13 +3797,24 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
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     if (bs->file &&
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         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
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         (ret & BDRV_BLOCK_OFFSET_VALID)) {
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+        int file_pnum;
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+
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         ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
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-                                        *pnum, pnum);
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+                                        *pnum, &file_pnum);
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         if (ret2 >= 0) {
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             /* Ignore errors.  This is just providing extra information, it
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              * is useful but not necessary.
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              */
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-            ret |= (ret2 & BDRV_BLOCK_ZERO);
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+            if (!file_pnum) {
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+                /* !file_pnum indicates an offset at or beyond the EOF; it is
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+                 * perfectly valid for the format block driver to point to such
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+                 * offsets, so catch it and mark everything as zero */
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+                ret |= BDRV_BLOCK_ZERO;
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+            } else {
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+                /* Limit request to the range reported by the protocol driver */
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+                *pnum = file_pnum;
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+                ret |= (ret2 & BDRV_BLOCK_ZERO);
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+            }
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         }
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     }
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-- 
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1.8.3.1
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