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| author | Richard W.M. Jones <rjones@redhat.com> | 2015-09-29 16:54:10 +0100 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2015-10-02 13:48:29 +0200 |
| commit | 73ba05d936e82fe01b2b2cf987bf3aecb4792af5 (patch) | |
| tree | 8402b957686a90af0310701e08cbc4319da12749 /hw/display/virtio-gpu-pci.c | |
| parent | 99b7e7756780cec03fe5175db0f53b2fffa9426b (diff) | |
| download | focaccia-qemu-73ba05d936e82fe01b2b2cf987bf3aecb4792af5.tar.gz focaccia-qemu-73ba05d936e82fe01b2b2cf987bf3aecb4792af5.zip | |
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>
Diffstat (limited to 'hw/display/virtio-gpu-pci.c')
0 files changed, 0 insertions, 0 deletions