Btrfs: fix sysfs warning and missing raid sysfs directories
In the 5.3 merge window, commit 7c7e3014 ("btrfs: sysfs: Replace default_attrs in ktypes with groups"), we started using the member "defaults_groups" for the kobject type "btrfs_raid_ktype". That leads to a series of warnings when running some test cases of fstests, such as btrfs/027, btrfs/124 and btrfs/176. The traces produced by those warnings are like the following: [116648.059212] kernfs: can not remove 'total_bytes', no directory [116648.060112] WARNING: CPU: 3 PID: 28500 at fs/kernfs/dir.c:1504 kernfs_remove_by_name_ns+0x75/0x80 (...) [116648.066482] CPU: 3 PID: 28500 Comm: umount Tainted: G W 5.3.0-rc3-btrfs-next-54 #1 (...) [116648.069376] RIP: 0010:kernfs_remove_by_name_ns+0x75/0x80 (...) [116648.072385] RSP: 0018:ffffabfd0090bd08 EFLAGS: 00010282 [116648.073437] RAX: 0000000000000000 RBX: ffffffffc0c11998 RCX: 0000000000000000 [116648.074201] RDX: ffff9fff603a7a00 RSI: ffff9fff603978a8 RDI: ffff9fff603978a8 [116648.074956] RBP: ffffffffc0b9ca2f R08: 0000000000000000 R09: 0000000000000001 [116648.075708] R10: ffff9ffe1f72e1c0 R11: 0000000000000000 R12: ffffffffc0b94120 [116648.076434] R13: ffffffffb3d9b4e0 R14: 0000000000000000 R15: dead000000000100 [116648.077143] FS: 00007f9cdc78a2c0(0000) GS:ffff9fff60380000(0000) knlGS:0000000000000000 [116648.077852] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [116648.078546] CR2: 00007f9fc4747ab4 CR3: 00000005c7832003 CR4: 00000000003606e0 [116648.079235] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [116648.079907] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [116648.080585] Call Trace: [116648.081262] remove_files+0x31/0x70 [116648.081929] sysfs_remove_group+0x38/0x80 [116648.082596] sysfs_remove_groups+0x34/0x70 [116648.083258] kobject_del+0x20/0x60 [116648.083933] btrfs_free_block_groups+0x405/0x430 [btrfs] [116648.084608] close_ctree+0x19a/0x380 [btrfs] [116648.085278] generic_shutdown_super+0x6c/0x110 [116648.085951] kill_anon_super+0xe/0x30 [116648.086621] btrfs_kill_super+0x12/0xa0 [btrfs] [116648.087289] deactivate_locked_super+0x3a/0x70 [116648.087956] cleanup_mnt+0xb4/0x160 [116648.088620] task_work_run+0x7e/0xc0 [116648.089285] exit_to_usermode_loop+0xfa/0x100 [116648.089933] do_syscall_64+0x1cb/0x220 [116648.090567] entry_SYSCALL_64_after_hwframe+0x49/0xbe [116648.091197] RIP: 0033:0x7f9cdc073b37 (...) [116648.100046] ---[ end trace 22e24db328ccadf8 ]--- [116648.100618] ------------[ cut here ]------------ [116648.101175] kernfs: can not remove 'used_bytes', no directory [116648.101731] WARNING: CPU: 3 PID: 28500 at fs/kernfs/dir.c:1504 kernfs_remove_by_name_ns+0x75/0x80 (...) [116648.105649] CPU: 3 PID: 28500 Comm: umount Tainted: G W 5.3.0-rc3-btrfs-next-54 #1 (...) [116648.107461] RIP: 0010:kernfs_remove_by_name_ns+0x75/0x80 (...) [116648.109336] RSP: 0018:ffffabfd0090bd08 EFLAGS: 00010282 [116648.109979] RAX: 0000000000000000 RBX: ffffffffc0c119a0 RCX: 0000000000000000 [116648.110625] RDX: ffff9fff603a7a00 RSI: ffff9fff603978a8 RDI: ffff9fff603978a8 [116648.111283] RBP: ffffffffc0b9ca41 R08: 0000000000000000 R09: 0000000000000001 [116648.111940] R10: ffff9ffe1f72e1c0 R11: 0000000000000000 R12: ffffffffc0b94120 [116648.112603] R13: ffffffffb3d9b4e0 R14: 0000000000000000 R15: dead000000000100 [116648.113268] FS: 00007f9cdc78a2c0(0000) GS:ffff9fff60380000(0000) knlGS:0000000000000000 [116648.113939] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [116648.114607] CR2: 00007f9fc4747ab4 CR3: 00000005c7832003 CR4: 00000000003606e0 [116648.115286] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [116648.115966] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [116648.116649] Call Trace: [116648.117326] remove_files+0x31/0x70 [116648.117997] sysfs_remove_group+0x38/0x80 [116648.118671] sysfs_remove_groups+0x34/0x70 [116648.119342] kobject_del+0x20/0x60 [116648.120022] btrfs_free_block_groups+0x405/0x430 [btrfs] [116648.120707] close_ctree+0x19a/0x380 [btrfs] [116648.121396] generic_shutdown_super+0x6c/0x110 [116648.122057] kill_anon_super+0xe/0x30 [116648.122702] btrfs_kill_super+0x12/0xa0 [btrfs] [116648.123335] deactivate_locked_super+0x3a/0x70 [116648.123961] cleanup_mnt+0xb4/0x160 [116648.124586] task_work_run+0x7e/0xc0 [116648.125210] exit_to_usermode_loop+0xfa/0x100 [116648.125830] do_syscall_64+0x1cb/0x220 [116648.126463] entry_SYSCALL_64_after_hwframe+0x49/0xbe [116648.127080] RIP: 0033:0x7f9cdc073b37 (...) [116648.135923] ---[ end trace 22e24db328ccadf9 ]--- These happen because, during the unmount path, we call kobject_del() for raid kobjects that are not fully initialized, meaning that we set their ktype (as btrfs_raid_ktype) through link_block_group() but we didn't set their parent kobject, which is done through btrfs_add_raid_kobjects(). We have this split raid kobject setup since commit 75cb379d ("btrfs: defer adding raid type kobject until after chunk relocation") in order to avoid triggering reclaim during contextes where we can not (either we are holding a transaction handle or some lock required by the transaction commit path), so that we do the calls to kobject_add(), which triggers GFP_KERNEL allocations, through btrfs_add_raid_kobjects() in contextes where it is safe to trigger reclaim. That change expected that a new raid kobject can only be created either when mounting the filesystem or after raid profile conversion through the relocation path. However, we can have new raid kobject created in other two cases at least: 1) During device replace (or scrub) after adding a device a to the filesystem. The replace procedure (and scrub) do calls to btrfs_inc_block_group_ro() which can allocate a new block group with a new raid profile (because we now have more devices). This can be triggered by test cases btrfs/027 and btrfs/176. 2) During a degraded mount trough any write path. This can be triggered by test case btrfs/124. Fixing this by adding extra calls to btrfs_add_raid_kobjects(), not only makes things more complex and fragile, can also introduce deadlocks with reclaim the following way: 1) Calling btrfs_add_raid_kobjects() at btrfs_inc_block_group_ro() or anywhere in the replace/scrub path will cause a deadlock with reclaim because if reclaim happens and a transaction commit is triggered, the transaction commit path will block at btrfs_scrub_pause(). 2) During degraded mounts it is essentially impossible to figure out where to add extra calls to btrfs_add_raid_kobjects(), because allocation of a block group with a new raid profile can happen anywhere, which means we can't safely figure out which contextes are safe for reclaim, as we can either hold a transaction handle or some lock needed by the transaction commit path. So it is too complex and error prone to have this split setup of raid kobjects. So fix the issue by consolidating the setup of the kobjects in a single place, at link_block_group(), and setup a nofs context there in order to prevent reclaim being triggered by the memory allocations done through the call chain of kobject_add(). Besides fixing the sysfs warnings during kobject_del(), this also ensures the sysfs directories for the new raid profiles end up created and visible to users (a bug that existed before the 5.3 commit 7c7e3014 ("btrfs: sysfs: Replace default_attrs in ktypes with groups")). Fixes: 75cb379d ("btrfs: defer adding raid type kobject until after chunk relocation") Fixes: 7c7e3014 ("btrfs: sysfs: Replace default_attrs in ktypes with groups") Signed-off-by: NFilipe Manana <fdmanana@suse.com> Reviewed-by: NDavid Sterba <dsterba@suse.com> Signed-off-by: NDavid Sterba <dsterba@suse.com>
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