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From ea2675a74ab31ec9938dd50b4954ea9d6ba5fb50 Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Tue, 18 Nov 2014 15:30:17 +0100
Subject: [PATCH 4/7] raw-posix: Fix raw_co_get_block_status() after EOF

Message-id: <1416324620-16229-5-git-send-email-mreitz@redhat.com>
Patchwork-id: 62439
O-Subject: [RHEL-7.1/7.0.z qemu-kvm PATCH v3 4/7] raw-posix: Fix raw_co_get_block_status() after EOF
Bugzilla: 1166605
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>

As its comment states, raw_co_get_block_status() should unconditionally
return 0 and set *pnum to 0 for after EOF.

An assertion after lseek(..., SEEK_HOLE) tried to catch this case by
asserting that errno != -ENXIO (which would indicate a position after
the EOF); but it should be errno != ENXIO instead. Regardless of that,
there should be no such assertion at all. If bdrv_getlength() returned
an outdated value and the image has been resized outside of qemu,
lseek() will return with errno == ENXIO. Just return that value as an
error then.

Setting *pnum to 0 and returning 0 should not be done here, as in that
case we should update the device length as well. So, from qemu's
perspective, the file has not been resized; it's just that there was an
error querying sectors beyond a certain point (the actual file size).

Additionally, nb_sectors should be clamped against the image end. This
was probably not an issue if FIEMAP or SEEK_HOLE/SEEK_DATA worked, but
the fallback did not take this case into account.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1414148280-17949-2-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit e6d7ec32dd315422a023ed3425fe36df8c274eeb)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/raw-posix.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 47b4b71..d04e683 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1314,10 +1314,6 @@ static int64_t try_seek_hole(BlockDriverState *bs, off_t start, off_t *data,
 
     *hole = lseek(s->fd, start, SEEK_HOLE);
     if (*hole == -1) {
-        /* -ENXIO indicates that sector_num was past the end of the file.
-         * There is a virtual hole there.  */
-        assert(errno != -ENXIO);
-
         return -errno;
     }
 
@@ -1357,6 +1353,7 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                                     int nb_sectors, int *pnum)
 {
     off_t start, data = 0, hole = 0;
+    int64_t total_size;
     int64_t ret;
 
     ret = fd_open(bs);
@@ -1365,6 +1362,15 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
     }
 
     start = sector_num * BDRV_SECTOR_SIZE;
+    total_size = bdrv_getlength(bs);
+    if (total_size < 0) {
+        return total_size;
+    } else if (start >= total_size) {
+        *pnum = 0;
+        return 0;
+    } else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
+        nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
+    }
 
     ret = try_seek_hole(bs, start, &data, &hole, pnum);
     if (ret < 0) {
-- 
1.8.3.1