On Tue, Feb 16, 2021 at 04:36:06PM +0000, Christoph Hellwig wrote: > On Tue, Feb 16, 2021 at 02:38:49PM +0100, Jan Kara wrote: > > Apparently there are several userspace programs that depend on being > > able to call BLKDISCARD ioctl without the ability to grab bdev > > exclusively - namely FUSE filesystems have the device open without > > O_EXCL (the kernel has the bdev open with O_EXCL) so the commit breaks > > fstrim(8) for such filesystems. Also LVM when shrinking LV opens PV and > > discards ranges released from LV but that PV may be already open > > exclusively by someone else (see bugzilla link below for more details). > > > > This reverts commit 384d87ef2c954fc58e6c5fd8253e4a1984f5fe02. > > I think that is a bad idea. We fixed the problem for a reason. > I think the right fix is to just do nothing if the device hasn't been > opened with O_EXCL and can't be reopened with it, just don't do anything > but also don't return an error. After all discard and thus > BLKDISCARD is purely advisory. A discard is advisory, but BLKZEROOUT is not, so something different should happen there. We were also planning to send a patch using this same pattern for Zone Reset to fix stale page cache issues after the reset, but we'll wait to see how this settles before sending that.
