| Message ID | 20250417211053.98700-1-stefanha@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | block/file-posix: allow BLKZEROOUT with -t writeback | expand |
diff --git a/block/file-posix.c b/block/file-posix.c index 56d1972d15..9ba0b68958 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -781,17 +781,6 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } #endif - if (S_ISBLK(st.st_mode)) { -#ifdef __linux__ - /* On Linux 3.10, BLKDISCARD leaves stale data in the page cache. Do - * not rely on the contents of discarded blocks unless using O_DIRECT. - * Same for BLKZEROOUT. - */ - if (!(bs->open_flags & BDRV_O_NOCACHE)) { - s->has_write_zeroes = false; - } -#endif - } #ifdef __FreeBSD__ if (S_ISCHR(st.st_mode)) { /*
The Linux BLKZEROOUT ioctl is only invoked when BDRV_O_NOCACHE is set because old kernels did not invalidate the page cache. In that case mixing BLKZEROOUT with buffered I/O could lead to corruption. However, Linux 4.9 commit 22dd6d356628 ("block: invalidate the page cache when issuing BLKZEROOUT") made BLKZEROOUT coherent with the page cache. I have checked that Linux 4.9+ kernels are shipped at least as far back as Debian 10 (buster), openSUSE Leap 15.2, and RHEL/CentOS 8. Use BLKZEROOUT with buffered I/O, mostly so `qemu-img ... -t writeback` can offload write zeroes. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- block/file-posix.c | 11 ----------- 1 file changed, 11 deletions(-)