From: Sam Edwards Date: Wed, 18 Mar 2026 02:37:33 +0000 (-0700) Subject: ceph: fix num_ops OBOE when crypto allocation fails X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=9748b9ecd8d7bb5af7d19ad815b7284dfb0a0b9c;p=ceph-client.git ceph: fix num_ops OBOE when crypto allocation fails move_dirty_folio_in_page_array() may fail if the file is encrypted, the dirty folio is not the first in the batch, and it fails to allocate a bounce buffer to hold the ciphertext. When that happens, ceph_process_folio_batch() simply redirties the folio and flushes the current batch -- it can retry that folio in a future batch. However, if this failed folio is not contiguous with the last folio that did make it into the batch, then ceph_process_folio_batch() has already incremented `ceph_wbc->num_ops`; because it doesn't follow through and add the discontiguous folio to the array, ceph_submit_write() -- which expects that `ceph_wbc->num_ops` accurately reflects the number of contiguous ranges (and therefore the required number of "write extent" ops) in the writeback -- will panic the kernel: BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops); This issue can be reproduced on affected kernels by writing to fscrypt-enabled CephFS file(s) with a 4KiB-written/4KiB-skipped/repeat pattern (total filesize should not matter) and gradually increasing the system's memory pressure until a bounce buffer allocation fails. Fix this crash by decrementing `ceph_wbc->num_ops` back to the correct value when move_dirty_folio_in_page_array() fails, but the folio already started counting a new (i.e. still-empty) extent. The defect corrected by this patch has existed since 2022 (see first `Fixes:`), but another bug blocked multi-folio encrypted writeback until recently (see second `Fixes:`). The second commit made it into 6.18.16, 6.19.6, and 7.0-rc1, unmasking the panic in those versions. This patch therefore fixes a regression (panic) introduced by cac190c7674f. Cc: stable@vger.kernel.org # v6.18+ Fixes: d55207717ded ("ceph: add encryption support to writepage and writepages") Fixes: cac190c7674f ("ceph: fix write storm on fscrypted files") Signed-off-by: Sam Edwards Tested-by: Viacheslav Dubeyko Reviewed-by: Viacheslav Dubeyko --- diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index 67be09747975..3d2ec18b5b45 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -1365,6 +1365,10 @@ void ceph_process_folio_batch(struct address_space *mapping, rc = move_dirty_folio_in_page_array(mapping, wbc, ceph_wbc, folio); if (rc) { + /* Did we just begin a new contiguous op? Nevermind! */ + if (ceph_wbc->len == 0) + ceph_wbc->num_ops--; + folio_redirty_for_writepage(wbc, folio); folio_unlock(folio); break;