From 7b62e66cbbfb463a39bf83e30bdbbb4b9e83fa03 Mon Sep 17 00:00:00 2001 From: Dennis Zhou Date: Wed, 11 Dec 2019 16:07:06 -0800 Subject: btrfs: punt all bios created in btrfs_submit_compressed_write() Compressed writes happen in the background via kworkers. However, this causes bios to be attributed to root bypassing any cgroup limits from the actual writer. We tag the first bio with REQ_CGROUP_PUNT, which will punt the bio to an appropriate cgroup specific workqueue and attribute the IO properly. However, if btrfs_submit_compressed_write() creates a new bio, we don't tag it the same way. Add the appropriate tagging for subsequent bios. Fixes: ec39f7696ccfa ("Btrfs: use REQ_CGROUP_PUNT for worker thread submitted bios") Reviewed-by: Chris Mason Signed-off-by: Dennis Zhou Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/compression.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'fs/btrfs/compression.c') diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index ee834ef7beb4..b08e16b8cebb 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -491,6 +491,10 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start, bio->bi_opf = REQ_OP_WRITE | write_flags; bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; + if (blkcg_css) { + bio->bi_opf |= REQ_CGROUP_PUNT; + bio_associate_blkg_from_css(bio, blkcg_css); + } bio_add_page(bio, page, PAGE_SIZE, 0); } if (bytes_left < PAGE_SIZE) { -- cgit From 46bcff2bfc5e6a8c638d3a32e4f6f6fa4bd01461 Mon Sep 17 00:00:00 2001 From: Dennis Zhou Date: Wed, 11 Dec 2019 15:20:15 -0800 Subject: btrfs: fix compressed write bio blkcg attribution Bio attribution is handled at bio_set_dev() as once we have a device, we have a corresponding request_queue and then can derive the current css. In special cases, we want to attribute to bio to someone else. This can be done by calling bio_associate_blkg_from_css() or kthread_associate_blkcg() depending on the scenario. Btrfs does this for compressed writeback as they are handled by kworkers, so the latter can be done here. Commit 1a41802701ec ("btrfs: drop bio_set_dev where not needed") removes early bio_set_dev() calls prior to submit_stripe_bio(). This breaks the above assumption that we'll have a request_queue when we are doing association. To fix this, switch to using kthread_associate_blkcg(). Without this, we crash in btrfs/024: [ 3052.093088] BUG: kernel NULL pointer dereference, address: 0000000000000510 [ 3052.107013] #PF: supervisor read access in kernel mode [ 3052.107014] #PF: error_code(0x0000) - not-present page [ 3052.107015] PGD 0 P4D 0 [ 3052.107021] Oops: 0000 [#1] SMP [ 3052.138904] CPU: 42 PID: 201270 Comm: kworker/u161:0 Kdump: loaded Not tainted 5.5.0-rc1-00062-g4852d8ac90a9 #712 [ 3052.138905] Hardware name: Quanta Tioga Pass Single Side 01-0032211004/Tioga Pass Single Side, BIOS F08_3A18 12/20/2018 [ 3052.138912] Workqueue: btrfs-delalloc btrfs_work_helper [ 3052.191375] RIP: 0010:bio_associate_blkg_from_css+0x1e/0x3c0 [ 3052.191379] RSP: 0018:ffffc900210cfc90 EFLAGS: 00010282 [ 3052.191380] RAX: 0000000000000000 RBX: ffff88bfe5573c00 RCX: 0000000000000000 [ 3052.191382] RDX: ffff889db48ec2f0 RSI: ffff88bfe5573c00 RDI: ffff889db48ec2f0 [ 3052.191386] RBP: 0000000000000800 R08: 0000000000203bb0 R09: ffff889db16b2400 [ 3052.293364] R10: 0000000000000000 R11: ffff88a07fffde80 R12: ffff889db48ec2f0 [ 3052.293365] R13: 0000000000001000 R14: ffff889de82bc000 R15: ffff889e2b7bdcc8 [ 3052.293367] FS: 0000000000000000(0000) GS:ffff889ffba00000(0000) knlGS:0000000000000000 [ 3052.293368] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3052.293369] CR2: 0000000000000510 CR3: 0000000002611001 CR4: 00000000007606e0 [ 3052.293370] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 3052.293371] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 3052.293372] PKRU: 55555554 [ 3052.293376] Call Trace: [ 3052.402552] btrfs_submit_compressed_write+0x137/0x390 [ 3052.402558] submit_compressed_extents+0x40f/0x4c0 [ 3052.422401] btrfs_work_helper+0x246/0x5a0 [ 3052.422408] process_one_work+0x200/0x570 [ 3052.438601] ? process_one_work+0x180/0x570 [ 3052.438605] worker_thread+0x4c/0x3e0 [ 3052.438614] kthread+0x103/0x140 [ 3052.460735] ? process_one_work+0x570/0x570 [ 3052.460737] ? kthread_mod_delayed_work+0xc0/0xc0 [ 3052.460744] ret_from_fork+0x24/0x30 Fixes: 1a41802701ec ("btrfs: drop bio_set_dev where not needed") Reported-by: Chris Murphy Signed-off-by: Dennis Zhou Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/compression.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/compression.c') diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index b08e16b8cebb..43e1660f450f 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -447,7 +447,7 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start, if (blkcg_css) { bio->bi_opf |= REQ_CGROUP_PUNT; - bio_associate_blkg_from_css(bio, blkcg_css); + kthread_associate_blkcg(blkcg_css); } refcount_set(&cb->pending_bios, 1); @@ -491,10 +491,8 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start, bio->bi_opf = REQ_OP_WRITE | write_flags; bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; - if (blkcg_css) { + if (blkcg_css) bio->bi_opf |= REQ_CGROUP_PUNT; - bio_associate_blkg_from_css(bio, blkcg_css); - } bio_add_page(bio, page, PAGE_SIZE, 0); } if (bytes_left < PAGE_SIZE) { @@ -521,6 +519,9 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start, bio_endio(bio); } + if (blkcg_css) + kthread_associate_blkcg(NULL); + return 0; } -- cgit