If a multipath device is removed, and check_path() checks one of its paths before multipathd processes either the uevent or the dm event from removing it, multipathd will recreate the removed device. This happens because check_path() will continute to check the removed device's former paths until an event arrives removing the device. A missing multpath device will cause the update_multipath_strings() call to fail, setting pp->dmstate to PSTATE_UNDEF. If the path is up, this dmstate will cause reinstate_path() to be called, which will also fail, because the multipath device doesn't exist. This will trigger a reload, restoring the recently removed device. This patchset handles this is two ways. The first two patches directly fix these issues in check_path(), so that a missing multipath device will no longer get recreated when checking one of its former paths. The other 5 patches add a "multipathd del maps" command, and make the mutipath command delegate flush operations to multipathd so multipathd's state remains in sync with the kernel's, while doing removes. One source of complexity in these patches is that multipath suspends the device with flushing before removing it, while multipathd doesn't. It does seem possible that the suspend could hang for a while, so I can understand multipathd not using it. However, that would take the multipath device getting opened and IO being issued, between the time when _dm_flush_map() verifies that the device isn't opened, and when it suspends the device. But more importantly, I don't understand how suspending the device is useful. If the device were to be opened between when _dm_flush_map() checks the usage, and when it tries to delete the device, device-mapper would simply fail the remove. And if the device isn't in use, there can't be any outstanding IO to flush. When this code was added in commit 9a4ff93, there was no check if the device was in use, and disabling queue_if_no_path could cause anything that had the device open to error out and close it. But now that multipath checks first if the device is open, I don't see the benefit to doing this anymore. Removing it would allow multipathd and multipath to use the same code to remove maps. Any thoughts? Benjamin Marzinski (7): libmultipath: change do_get_info returns multipathd: fix check_path errors with removed map libmultipath: make dm_flush_maps only return 0 on success multipathd: add "del maps" multipathd command multipath: make flushing maps work like other commands multipath: delegate flushing maps to multipathd multipath: add option to skip multipathd delegation libmultipath/config.h | 4 ++- libmultipath/configure.h | 3 --- libmultipath/devmapper.c | 41 ++++++++++++++++++------------- libmultipath/devmapper.h | 3 ++- multipath/main.c | 51 +++++++++++++++++++++++++++------------ multipath/multipath.8 | 16 ++++++++---- multipathd/cli.c | 1 + multipathd/cli_handlers.c | 19 +++++++++++++++ multipathd/cli_handlers.h | 1 + multipathd/main.c | 39 ++++++++++++------------------ multipathd/main.h | 1 + 11 files changed, 114 insertions(+), 65 deletions(-) -- 2.17.2 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
