From d058befe667eb24da6884a78efc23443dd9de566 Mon Sep 17 00:00:00 2001

From: Max Reitz <mreitz@redhat.com>

Date: Tue, 18 Nov 2014 15:30:17 +0100

Subject: [PATCH 38/41] 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: 1160237

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an outdated value and the image has been resized outside of qemu,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 781ebf3..75a81b1 100644

--- a/block/raw-posix.c

+++ b/block/raw-posix.c

@@ -1362,10 +1362,6 @@ 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;

     }

@@ -1405,6 +1401,7 @@ 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);

@@ -1413,6 +1410,15 @@ 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