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Richard W.M. Jones 73ba05d936 block/raw-posix: Open file descriptor O_RDWR to work around glibc posix_fallocate emulation issue. 
https://bugzilla.redhat.com/show_bug.cgi?id=1265196

The following command fails on an NFS mountpoint:

  $ qemu-img create -f qcow2 -o preallocation=falloc disk.img 262144
  Formatting 'disk.img', fmt=qcow2 size=262144 encryption=off cluster_size=65536 preallocation='falloc' lazy_refcounts=off
  qemu-img: disk.img: Could not preallocate data for the new file: Bad file descriptor

The reason turns out to be because NFS doesn't support the
posix_fallocate call.  glibc emulates it instead.  However glibc's
emulation involves using the pread(2) syscall.  The pread syscall
fails with EBADF if the file descriptor is opened without the read
open-flag (ie. open (..., O_WRONLY)).

I contacted glibc upstream about this, and their response is here:

  https://bugzilla.redhat.com/show_bug.cgi?id=1265196#c9

There are two possible fixes: Use Linux fallocate directly, or (this
fix) work around the problem in qemu by opening the file with O_RDWR
instead of O_WRONLY.

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1265196
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
 		2015-10-02 13:48:29 +02:00
..
Makefile.objs block: convert quorum blockdrv to use crypto APIs 2015-07-08 13:11:01 +02:00
accounting.c block: add accounting for merged requests 2015-02-06 17:24:21 +01:00
archipelago.c block: remove superfluous '\n' around error_report/error_setg 2015-03-10 08:15:33 +03:00
backup.c Backup: don't do copy-on-read in before_write_notifier 2015-09-25 08:37:07 -04:00
blkdebug.c block: Move flag inheritance to bdrv_open_inherit() 2015-06-12 17:04:59 +02:00
blkverify.c block: Move flag inheritance to bdrv_open_inherit() 2015-06-12 17:04:59 +02:00
block-backend.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
bochs.c block: Use g_new() & friends to avoid multiplying sizes 2014-08-20 11:51:28 +02:00
cloop.c cloop: Handle failure for potentially large allocations 2014-08-15 15:07:15 +02:00
commit.c block: Allow specifying driver-specific options to reopen 2015-09-14 16:51:36 +02:00
curl.c block/curl: Don't lose original error when a connection fails. 2015-07-14 21:50:13 -04:00
dmg.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
gluster.c block: don't convert file size to sector size 2014-09-12 15:43:06 +02:00
io.c block: Introduce a new API bdrv_co_no_copy_on_readv() 2015-09-25 08:37:07 -04:00
iscsi.c block/iscsi: validate block size returned from target 2015-09-07 18:14:03 +02:00
linux-aio.c linux-aio: simplify removal of completed iocbs from the list 2014-12-12 16:57:55 +00:00
mirror.c block: mirror - fix full sync mode when target does not support zero init 2015-10-01 15:02:21 -04:00
nbd-client.c nbd: Set block size to BDRV_SECTOR_SIZE 2015-03-18 12:07:01 +01:00
nbd-client.h nbd: Set block size to BDRV_SECTOR_SIZE 2015-03-18 12:07:01 +01:00
nbd.c nbd: convert to use the QAPI SocketAddress object 2015-09-25 12:04:40 +02:00
nfs.c block/nfs: cache allocated filesize for read-only files 2015-09-25 08:37:07 -04:00
null.c block/null: Support reopen 2015-04-28 15:36:09 +02:00
parallels.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
qapi.c qerror: Finally unused, clean up 2015-06-22 18:20:40 +02:00
qcow.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
qcow2-cache.c qcow2: Rename BDRVQcowState to BDRVQcow2State 2015-09-14 16:51:36 +02:00
qcow2-cluster.c qcow2: Make size_to_clusters() return uint64_t 2015-09-14 16:51:37 +02:00
qcow2-refcount.c qcow2: Make qcow2_alloc_bytes() more explicit 2015-09-14 16:51:37 +02:00
qcow2-snapshot.c qcow2: Rename BDRVQcowState to BDRVQcow2State 2015-09-14 16:51:36 +02:00
qcow2.c qcow2: Support updating driver-specific options in reopen 2015-09-14 16:51:37 +02:00
qcow2.h qcow2: Make size_to_clusters() return uint64_t 2015-09-14 16:51:37 +02:00
qed-check.c block: Use g_new() & friends to avoid multiplying sizes 2014-08-20 11:51:28 +02:00
qed-cluster.c Use glib memory allocation and free functions 2011-08-20 23:01:08 -05:00
qed-gencb.c block: Rename BlockDriverCompletionFunc to BlockCompletionFunc 2014-10-20 13:41:27 +02:00
qed-l2-cache.c qed: do not evict in-use L2 table cache entries 2012-03-12 15:14:06 +01:00
qed-table.c block: Rename BlockDriverCompletionFunc to BlockCompletionFunc 2014-10-20 13:41:27 +02:00
qed.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
qed.h qed: Really remove unused field QEDAIOCB.finished 2015-02-06 17:24:21 +01:00
quorum.c quorum: validate vote threshold against num_children even if read-pattern is fifo 2015-09-04 21:00:32 +02:00
raw-aio.h linux-aio: drop return code from laio_io_unplug and ioq_submit 2014-12-12 16:57:55 +00:00
raw-posix.c block/raw-posix: Open file descriptor O_RDWR to work around glibc posix_fallocate emulation issue. 2015-10-02 13:48:29 +02:00
raw-win32.c raw-win32: Fix write request error handling 2015-10-02 13:48:29 +02:00
raw_bsd.c block: Add driver methods to probe blocksizes and geometry 2015-03-10 14:02:22 +01:00
rbd.c rbd: fix ceph settings precedence 2015-07-14 17:15:23 +02:00
sheepdog.c sheepdog: refine discard support 2015-09-25 10:25:19 -04:00
snapshot.c block: Use bdrv_drain to replace uncessary bdrv_drain_all 2015-07-07 14:27:14 +01:00
ssh.c block/ssh: Avoid segfault if inet_connect doesn't set errno. 2015-07-28 00:19:05 -04:00
stream.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
throttle-groups.c throttle: Check current timers before updating any_timer_armed[] 2015-06-23 15:06:16 +01:00
vdi.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
vhdx-endian.c block: VHDX endian fixes 2014-08-15 15:07:14 +02:00
vhdx-log.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
vhdx.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +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 next_cluster_sector for compressed write 2015-09-14 16:51:37 +02:00
vpc.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
vvfat.c block: Drop drv parameter from bdrv_open() 2015-09-14 16:51:36 +02:00
win32-aio.c block: Rename BlockDriverCompletionFunc to BlockCompletionFunc 2014-10-20 13:41:27 +02:00
write-threshold.c block: Fix block-set-write-threshold not to use funky error class 2015-03-16 17:07:25 +01:00