Hi Mariusz & Blazej, Thanks for the review and file PR. Please check other comments below. On 2/12/25 1:51 PM, Blazej Kucman wrote:
On Wed, 12 Feb 2025 11:07:13 +0100 Mariusz Tkaczyk <mtkaczyk@xxxxxxxxxx> wrote:Hello Junxiao, Thanks for solid and complete explanation! On Mon, 10 Feb 2025 13:22:25 -0800 Junxiao Bi <junxiao.bi@xxxxxxxxxx> wrote:When manager thread detects new array, it will invoke manage_new(). For imsm array, it will further invoke imsm_open_new(). Since commit bbab0940fa75("imsm: write bad block log on metadata sync"), it preallocates bad block log when opening the array, that requires increasing the mpb buffer size. To do that, imsm_open_new() invokes imsm_update_metadata_locally(), which first uses imsm_prepare_update() to allocate a larger mpb buffer and store it at "mpb->next_buf", and then invoke imsm_process_update() to copy the content from current mpb buffer "mpb->buf" to "mpb->next_buf", and then free the current mpb buffer and set the new buffer as current. There is a small race window, when monitor thread is syncing metadata, it grabs current buffer pointer in imsm_sync_metadata()->write_super_imsm(), but before flushing the buffer to disk, manager thread does above switching buffer which frees current buffer, then monitor thread will run into use-after-free issue and could cause on-disk metadata corruption. If system keeps running, further metadata update could fix the corruption, because after switching buffer, the new buffer will contain good metadata, but if panic/power cycle happens while disk metadata is corrupted, the system will run into bootup failure if array is used as root, otherwise the array can not be assembled after boot if not used as root. This issue will not happen for imsm array with only one member array, because the memory array has not be opened yet, monitor thread will not do any metadata updates. This can happen for imsm array with at lease two member array, in the following two scenarios: 1. Restarting mdmon process with at least two member array This will happen during system boot up or user restart mdmon after mdadm upgrade 2. Adding new member array to exist imsm array with at least one member array. To fix this, delay the switching buffer operation to monitor thread. Fixes: bbab0940fa75 ("imsm: write bad block log on metadata sync") Signed-off-by: Junxiao Bi <junxiao.bi@xxxxxxxxxx> --- managemon.c | 6 ++++++ super-intel.c | 14 +++++++++++--- 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/managemon.c b/managemon.c index d79813282457..855c85c3da92 100644 --- a/managemon.c +++ b/managemon.c @@ -726,6 +726,7 @@ static void manage_new(struct mdstat_ent *mdstat, int i, inst; int failed = 0; char buf[SYSFS_MAX_BUF_SIZE]; + struct metadata_update *update = NULL;If you are adding something new here, please follow reversed Christmas tree convention.
got it, i will move this new variable to the top of the function in v2. Should i move variable "buf" to proper location as well?
/* check if array is ready to be monitored */if (!mdstat->active || !mdstat->level) @@ -824,9 +825,14 @@ static void manage_new(struct mdstat_ent *mdstat, /* if everything checks out tell the metadata handler we want to * manage this instance */ + container->update_tail = &update; if (!aa_ready(new) || container->ss->open_new(container, new, inst) < 0) { + container->update_tail = NULL; goto error; } else { + if (update) + queue_metadata_update(update); + container->update_tail = NULL; replace_array(container, victim, new); if (failed) { new->check_degraded = 1; diff --git a/super-intel.c b/super-intel.c index cab841980830..4988eef191da 100644 --- a/super-intel.c +++ b/super-intel.c @@ -8467,12 +8467,15 @@ static int imsm_count_failed(struct intel_super *super, struct imsm_dev *dev, return failed; }+static int imsm_prepare_update(struct supertype *st,+ struct metadata_update *update); static int imsm_open_new(struct supertype *c, struct active_array *a, int inst) { struct intel_super *super = c->sb; struct imsm_super *mpb = super->anchor; - struct imsm_update_prealloc_bb_mem u; + struct imsm_update_prealloc_bb_mem *u; + struct metadata_update mu;if (inst >= mpb->num_raid_devs) {pr_err("subarry index %d, out of range\n", inst); @@ -8482,8 +8485,13 @@ static int imsm_open_new(struct supertype *c, struct active_array *a, dprintf("imsm: open_new %d\n", inst); a->info.container_member = inst;- u.type = update_prealloc_badblocks_mem;- imsm_update_metadata_locally(c, &u, sizeof(u)); + u = xmalloc(sizeof(*u)); + u->type = update_prealloc_badblocks_mem; + mu.len = sizeof(*u); + mu.buf = (char *)u; + imsm_prepare_update(c, &mu); + if (c->update_tail) + append_metadata_update(c, u, sizeof(*u));return 0;}I don't see issues, so you have my approve but it is Intel owned code and I need Intel to approve. . Blazej, Could you please create Github PR with a patch if Intel is good with the change? I would like to see test results before merge.Hi I've added a PR on github, I'll review this change by the end of the week. PR: https://github.com/md-raid-utilities/mdadm/pull/152
I see this error reported from PR test, may i know how to access these two logs? This fix is for imsm, and ->open_new for ddf not even touch "update_tail", not sure how this could cause ddf test failure.
/home/vagrant/host/mdadm/tests/10ddf-create-fail-rebuild... Execution time (seconds): 46 FAILED - see /var/tmp/10ddf-create-fail-rebuild.log and /var/tmp/fail10ddf-create-fail-rebuild.log for details /home/vagrant/host/mdadm/tests/10ddf-fail-readd... Execution time (seconds): 27 FAILED - see /var/tmp/10ddf-fail-readd.log and /var/tmp/fail10ddf-fail-readd.log for details
Thanks, Junxiao.
Thanks, BlazejThanks, Mariusz
