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qemu-e2k/block
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Eric Blake 9cdcfd9f7a block: Uniform handling of 0-length bdrv_get_block_status() 
Handle a 0-length block status request up front, with a uniform
return value claiming the area is not allocated.

Most callers don't pass a length of 0 to bdrv_get_block_status()
and friends; but it definitely happens with a 0-length read when
copy-on-read is enabled.  While we could audit all callers to
ensure that they never make a 0-length request, and then assert
that fact, it was just as easy to fix things to always report
success (as long as the callers are careful to not go into an
infinite loop).  However, we had inconsistent behavior on whether
the status is reported as allocated or defers to the backing
layer, depending on what callbacks the driver implements, and
possibly wasting quite a few CPU cycles to get to that answer.
Consistently reporting unallocated up front doesn't really hurt
anything, and makes it easier both for callers (0-length requests
now have well-defined behavior) and for drivers (drivers don't
have to deal with 0-length requests).

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
 		2017-10-06 16:28:58 +02:00
..
Makefile.objs block: add throttle block filter driver 2017-09-06 10:12:02 +02:00
accounting.c block: make accounting thread-safe 2017-06-16 07:55:00 +08:00
backup.c dirty-bitmap: Change bdrv_dirty_iter_next() to report byte offset 2017-10-06 16:28:58 +02:00
blkdebug.c block: add default implementations for bdrv_co_get_block_status() 2017-09-04 18:31:13 +02:00
blkreplay.c block: change variable names in BlockDriverState 2017-06-26 14:54:46 +02:00
blkverify.c blkverify: Catch bs->exact_filename overflow 2017-06-26 14:54:46 +02:00
block-backend.c block: tidy ThrottleGroupMember initializations 2017-09-05 16:47:52 +02:00
bochs.c block: do not set BDS read_only if copy_on_read enabled 2017-04-24 15:09:33 -04:00
cloop.c block: do not set BDS read_only if copy_on_read enabled 2017-04-24 15:09:33 -04:00
commit.c commit: Remove overlay_bs 2017-10-06 16:28:58 +02:00
crypto.c block: Add PreallocMode to bdrv_truncate() 2017-07-11 17:45:01 +02:00
crypto.h qcow: convert QCow to use QCryptoBlock for encryption 2017-07-11 17:44:56 +02:00
curl.c curl: do not do aio_poll when waiting for a free CURLState 2017-05-16 10:34:50 -04:00
dirty-bitmap.c dirty-bitmap: Convert internal hbitmap size/granularity 2017-10-06 16:28:58 +02:00
dmg-bz2.c dmg: Move libbz2 code to dmg-bz2.so 2016-10-07 14:14:06 +02:00
dmg.c dmg: use DIV_ROUND_UP 2017-08-31 12:29:07 +02:00
dmg.h dmg: Move libbz2 code to dmg-bz2.so 2016-10-07 14:14:06 +02:00
file-posix.c file-posix: Clear out first sector in hdev_create 2017-09-26 14:46:23 +02:00
file-win32.c qapi: Change data type of the FOO_lookup generated for enum FOO 2017-09-04 13:09:13 +02:00
gluster.c qapi: Change data type of the FOO_lookup generated for enum FOO 2017-09-04 13:09:13 +02:00
io.c block: Uniform handling of 0-length bdrv_get_block_status() 2017-10-06 16:28:58 +02:00
iscsi-opts.c block/iscsi: statically link qemu_iscsi_opts 2017-01-27 18:07:58 +01:00
iscsi.c scsi: move block/scsi.h to include/scsi/constants.h 2017-09-19 14:09:31 +02:00
linux-aio.c block: explicitly acquire aiocontext in aio callbacks that need it 2017-02-21 11:39:39 +00:00
mirror.c mirror: Switch mirror_dirty_init() to byte-based iteration 2017-10-06 16:28:58 +02:00
nbd-client.c block/nbd-client: nbd_co_send_request: fix return code 2017-09-25 08:21:26 -05:00
nbd-client.h nbd-client: avoid spurious qio_channel_yield() re-entry 2017-08-23 11:22:15 -05:00
nbd.c nbd: Implement NBD_INFO_BLOCK_SIZE on client 2017-07-14 12:04:42 +02:00
nfs.c qapi: Mechanically convert FOO_lookup[...] to FOO_str(...) 2017-09-04 13:09:13 +02:00
null.c block/null: Remove 'filename' option 2017-08-08 15:19:16 +02:00
parallels.c qapi: drop the sentinel in enum array 2017-09-04 13:09:13 +02:00
qapi.c block: move ThrottleGroup membership to ThrottleGroupMember 2017-09-05 16:47:51 +02:00
qcow.c qcow: Check failure of bdrv_getlength() and bdrv_truncate() 2017-09-04 18:33:00 +02:00
qcow2-bitmap.c qcow2: Switch store_bitmap_data() to byte-based iteration 2017-10-06 16:28:58 +02:00
qcow2-cache.c qcow2: add qcow2_cache_discard 2017-09-26 15:00:32 +02:00
qcow2-cluster.c qcow2: add shrink image support 2017-09-26 15:00:32 +02:00
qcow2-refcount.c qcow2: add shrink image support 2017-09-26 15:00:32 +02:00
qcow2-snapshot.c qcow2: Discard/zero clusters by byte count 2017-05-11 14:28:07 +02:00
qcow2.c qcow2: Switch qcow2_measure() to byte-based iteration 2017-10-06 16:28:58 +02:00
qcow2.h qcow2: add shrink image support 2017-09-26 15:00:32 +02:00
qed-check.c qed: Use DIV_ROUND_UP 2016-06-07 18:19:24 +03:00
qed-cluster.c qed: protect table cache with CoMutex 2017-07-17 11:34:11 +08:00
qed-l2-cache.c qed: protect table cache with CoMutex 2017-07-17 11:34:11 +08:00
qed-table.c qed: protect table cache with CoMutex 2017-07-17 11:34:11 +08:00
qed.c qapi: Mechanically convert FOO_lookup[...] to FOO_str(...) 2017-09-04 13:09:13 +02:00
qed.h qed: protect table cache with CoMutex 2017-07-17 11:34:11 +08:00
quorum.c qapi: Change data type of the FOO_lookup generated for enum FOO 2017-09-04 13:09:13 +02:00
raw-format.c block: remove unused bdrv_media_changed 2017-09-04 18:31:13 +02:00
rbd.c qapi: Mechanically convert FOO_lookup[...] to FOO_str(...) 2017-09-04 13:09:13 +02:00
replication.c block: Add reopen_queue to bdrv_child_perm() 2017-09-26 14:46:23 +02:00
sheepdog.c Merge QEMU I/O 2017/09/05 v2 2017-09-05 14:14:33 +01:00
snapshot.c qobject: Use simpler QDict/QList scalar insertion macros 2017-05-09 09:13:51 +02:00
ssh.c util: remove the obsolete non-blocking connect 2017-09-05 13:21:58 +01:00
stream.c block: Make bdrv_is_allocated_above() byte-based 2017-07-10 13:18:07 +02:00
throttle-groups.c block/throttle-groups.c: allocate RestartData on the heap 2017-09-26 14:46:23 +02:00
throttle.c block: add throttle block filter driver 2017-09-06 10:12:02 +02:00
trace-events block: move trace probes into bdrv_co_preadv|pwritev 2017-08-07 09:39:35 +01:00
vdi.c vdi: make it thread-safe 2017-07-17 11:28:15 +08:00
vhdx-endian.c vhdx: Use QEMU UUID API 2016-09-23 11:42:52 +08:00
vhdx-log.c vhdx: use QEMU_ALIGN_DOWN 2017-08-31 12:29:07 +02:00
vhdx.c block/vhdx: check for offset overflow to bdrv_truncate() 2017-08-08 14:37:00 +02:00
vhdx.h block: vhdx - update PAYLOAD_BLOCK_UNMAPPED value to match 1.00 spec 2014-12-12 15:42:22 +00:00
vmdk.c vmdk: Fix error handling/reporting of vmdk_check 2017-08-08 15:19:16 +02:00
vpc.c vpc: use DIV_ROUND_UP 2017-08-31 12:29:07 +02:00
vvfat.c block: Add reopen_queue to bdrv_child_perm() 2017-09-26 14:46:23 +02:00
vxhs.c qobject: Use simpler QDict/QList scalar insertion macros 2017-05-09 09:13:51 +02:00
win32-aio.c block: explicitly acquire aiocontext in aio callbacks that need it 2017-02-21 11:39:39 +00:00
write-threshold.c block: use bdrv_add_before_write_notifier 2016-10-07 13:34:07 +02:00