The race condition is noticed between disk_add() and disk attributes, on virtio-blk hotplug. Userspace listens to the KOBJ_ADD uevent generated in add_disk(). At that point we haven't created the serial attribute file, therefore depending on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get created. As pointed out by Christoph Hellwig in the specific fix [1], virtio-blk is not the only driver that suffers from this, so we cannot count on every driver to send events manually. Moreover as suggested in uevent documentation, it is advised to defer the KOBJ_ADD event until all attributes are ready: Documentation/kobject.txt: > Use the KOBJ_ADD action for when the kobject is first added to the kernel. > This should be done only after any attributes or children of the kobject > have been initialized properly, as userspace will instantly start to look > for them when this call happens. Unfortunately it seems impossible to fix this generally without touching the offending callers. The approach I'm proposing here is adding a flag to suppress uevent in add_disk(), which is patch 1, then in later patches, convert any caller to only trigger the uevent when attributes are added. [1] https://lkml.org/lkml/2016/6/28/550 Fam Zheng (12): genhd: Add "gen_uevent" parameter to add_disk genhd: Honor gen_uevent and add disk_gen_uevents virtio-blk: Generate uevent after attribute available axonrom: Generate uevent after attribute available aoeblk: Generate uevent after attribute available mtip32xx: Generate uevent after attribute available pktcdvd: Generate uevent after attribute available zram: Generate uevent after attribute available md: Generate uevent after attribute available mmc: Generate uevent after attribute available mtd: Generate uevent after attribute available nvme: Generate uevent after attribute available arch/m68k/emu/nfblock.c | 2 +- arch/powerpc/sysdev/axonram.c | 3 ++- arch/um/drivers/ubd_kern.c | 2 +- arch/xtensa/platforms/iss/simdisk.c | 2 +- block/genhd.c | 26 +++++++++++++++++++++----- drivers/block/DAC960.c | 2 +- drivers/block/amiflop.c | 2 +- drivers/block/aoe/aoeblk.c | 3 ++- drivers/block/ataflop.c | 2 +- drivers/block/brd.c | 4 ++-- drivers/block/cciss.c | 2 +- drivers/block/drbd/drbd_main.c | 2 +- drivers/block/floppy.c | 2 +- drivers/block/hd.c | 2 +- drivers/block/loop.c | 2 +- drivers/block/mg_disk.c | 2 +- drivers/block/mtip32xx/mtip32xx.c | 3 ++- drivers/block/nbd.c | 2 +- drivers/block/null_blk.c | 2 +- drivers/block/osdblk.c | 2 +- drivers/block/paride/pcd.c | 2 +- drivers/block/paride/pd.c | 2 +- drivers/block/paride/pf.c | 2 +- drivers/block/pktcdvd.c | 4 +++- drivers/block/ps3disk.c | 2 +- drivers/block/ps3vram.c | 2 +- drivers/block/rbd.c | 2 +- drivers/block/rsxx/dev.c | 2 +- drivers/block/skd_main.c | 2 +- drivers/block/sunvdc.c | 2 +- drivers/block/swim.c | 2 +- drivers/block/swim3.c | 2 +- drivers/block/sx8.c | 2 +- drivers/block/umem.c | 2 +- drivers/block/virtio_blk.c | 3 ++- drivers/block/xen-blkfront.c | 2 +- drivers/block/xsysace.c | 2 +- drivers/block/z2ram.c | 2 +- drivers/block/zram/zram_drv.c | 3 ++- drivers/cdrom/gdrom.c | 2 +- drivers/ide/ide-cd.c | 2 +- drivers/ide/ide-gd.c | 2 +- drivers/lightnvm/core.c | 2 +- drivers/md/bcache/super.c | 4 ++-- drivers/md/dm.c | 2 +- drivers/md/md.c | 3 ++- drivers/memstick/core/ms_block.c | 2 +- drivers/memstick/core/mspro_block.c | 2 +- drivers/mmc/card/block.c | 3 ++- drivers/mtd/mtd_blkdevs.c | 3 ++- drivers/mtd/ubi/block.c | 2 +- drivers/nvdimm/blk.c | 2 +- drivers/nvdimm/btt.c | 2 +- drivers/nvdimm/pmem.c | 2 +- drivers/nvme/host/core.c | 3 ++- drivers/s390/block/dasd_genhd.c | 2 +- drivers/s390/block/dcssblk.c | 2 +- drivers/s390/block/scm_blk.c | 2 +- drivers/s390/block/xpram.c | 2 +- drivers/sbus/char/jsflash.c | 2 +- drivers/scsi/sd.c | 2 +- drivers/scsi/sr.c | 2 +- drivers/staging/lustre/lustre/llite/lloop.c | 2 +- include/linux/genhd.h | 3 ++- 64 files changed, 98 insertions(+), 70 deletions(-) -- 2.9.0 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
