Hi,

I hit a fun issue with doveadm when migrating from dovecot 2.2.36 (1f10bfa63) to 2.3.19.1 (9b53102964) (CentOS 7 to Debian 12).

When running doveadm -v -D backup -R -u "user@name" tcp:localhost:1234, I found that the first sync would always work, but subsequent runs of the command would cause doveadm to reach a subfolder (Archives/2008 in the example below) and then silently mmap() increasing powers of 2 before the OOM killer finally got it. Deleting the source folder caused it to remain stuck on the same folder, but for the deletion event.

I switched memory overcommit off to force a crash, and got a gdb backtrace:

#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at ./nptl/pthread_kill.c:44 #1  0x00007ffff786bd9f in __pthread_kill_internal (signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:78 #2  0x00007ffff781cf32 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26 #3  0x00007ffff7807472 in __GI_abort () at ./stdlib/abort.c:79 #4  0x00007ffff7b4ffae in default_fatal_finish (status=0, type=LOG_TYPE_PANIC) at ../lib/failures.c:465 #5  fatal_handler_real (ctx=<optimized out>, format=<optimized out>, args=<optimized out>) at ../lib/failures.c:477 #6  0x00007ffff7bfa081 in default_fatal_handler (ctx=<optimized out>, format=<optimized out>, args=<optimized out>) at ../lib/failures.c:485 #7  0x00007ffff7b5017c in i_panic (format=0x7ffff7c5d748 "data stack: Out of memory when allocating %zu bytes") at ../lib/failures.c:530 #8  0x00007ffff7b4f67f in mem_block_alloc (min_size=min_size@entry=16) at ../lib/data-stack.c:386 #9  0x00007ffff7bf8b60 in t_malloc_real (size=<optimized out>, permanent=<optimized out>) at ../lib/data-stack.c:492 #10 0x00007ffff7c348f1 in t_strdup_until (start=start@entry=0x55555565f440, end=end@entry=0x55555565f448) at ../lib/strfuncs.c:270 #11 0x00005555555adc62 in convert_name_to_remote_sep (name=0x55555565f440 "Archives/2008", tree=0x55555564e188) at dsync/dsync-mailbox-tree.c:270 #12 dsync_mailbox_tree_build_name128_remotesep_hash (tree=0x55555564e188) at dsync/dsync-mailbox-tree.c:315 #13 dsync_mailbox_tree_find_delete (tree=0x55555564e188, del=0x5555556469f0) at dsync/dsync-mailbox-tree.c:405 #14 0x00005555555a4195 in dsync_brain_mailbox_tree_add_delete (tree=0x55555564e188, other_tree=0x55555564f5f8, other_del=0x5555556469f0, node_r=0x7fffffffe350, status_r=0x7fffffffe348) at dsync/dsync-brain-mailbox-tree.c:504 #15 0x00005555555a44cd in dsync_brain_recv_mailbox_tree_deletes (brain=0x55555564b2d8) at dsync/dsync-brain-mailbox-tree.c:590 #16 0x00005555555a5365 in dsync_brain_run_real (brain=brain@entry=0x55555564b2d8, changed_r=changed_r@entry=0x7fffffffe453) at dsync/dsync-brain.c:709 #17 0x00005555555a59f9 in dsync_brain_run (changed_r=0x7fffffffe453, brain=0x55555564b2d8) at dsync/dsync-brain.c:752 #18 dsync_brain_run (changed_r=0x7fffffffe453, brain=0x55555564b2d8) at dsync/dsync-brain.c:740 #19 dsync_brain_run_io (context=<optimized out>) at dsync/dsync-brain.c:113 #20 dsync_brain_run_io (context=0x55555564b2d8) at dsync/dsync-brain.c:100 #21 0x00005555555b23df in dsync_ibc_stream_input (ibc=0x555555646720) at dsync/dsync-ibc-stream.c:232 #22 0x00007ffff7c11cd9 in io_loop_call_io (io=0x5555556418f0) at ../lib/ioloop.c:737 #23 0x00007ffff7c13aa2 in io_loop_handler_run_internal (ioloop=ioloop@entry=0x55555560bf40) at ../lib/ioloop-epoll.c:222 #24 0x00007ffff7c13b50 in io_loop_handler_run (ioloop=ioloop@entry=0x55555560bf40) at ../lib/ioloop.c:789 #25 0x00007ffff7c13d10 in io_loop_run (ioloop=0x55555560bf40) at ../lib/ioloop.c:762 #26 0x000055555558b22e in cmd_dsync_run_remote (user=0x555555637248) at ./src/doveadm/doveadm-dsync.c:543 #27 cmd_dsync_run (_ctx=0x55555561f288, user=0x555555637248) at ./src/doveadm/doveadm-dsync.c:750 #28 0x000055555558bd12 in doveadm_mail_next_user (ctx=0x55555561f288, error_r=0x7fffffffe818) at ./src/doveadm/doveadm-mail.c:464 #29 0x000055555558cf45 in doveadm_mail_cmd_exec (wildcard_user=0x0, ctx=0x55555561f288) at ./src/doveadm/doveadm-mail.c:659 #30 doveadm_cmd_ver2_to_mail_cmd_wrapper (cctx=0x7fffffffe970) at ./src/doveadm/doveadm-mail.c:988 #31 0x0000555555597622 in doveadm_cmd_run_ver2 (argc=5, argv=0x55555560ba38, cctx=cctx@entry=0x7fffffffe970) at ./src/doveadm/doveadm-cmd.c:465 #32 0x0000555555597697 in doveadm_cmd_try_run_ver2 (cmd_name=<optimized out>, argc=<optimized out>, argv=<optimized out>, cctx=0x7fffffffe970) at ./src/doveadm/doveadm-cmd.c:363 #33 0x000055555557919a in main (argc=<optimized out>, argv=<optimized out>) at ./src/doveadm/doveadm.c:361

Neither server had a separator set in the inbox namespace. Having identified the convert_name_to_remote_sep function as the likely trigger point I set the separator to / on both ends, and doveadm backup now runs without issue.

Can provide config if helpful but I think probably irrelevant to this one - the namespace config is the default other than the separator item. May be worth mentioning that having the separator set can avoid this condition in the doveadm backup docs - this took me a while to figure out!

-- Cheers, James Harrison