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ceph: fix leaked inode reference on writeback abort at umount

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ceph_dirty_folio() takes a wrbuffer claim on each newly dirtied folio: it
bumps i_wrbuffer_ref (taking an ihold() on the 0->1 transition) and
attaches the snap_context to folio->private.  That claim is released only
by ceph_put_wrbuffer_cap_refs(), which for a submitted write runs from
writepages_finish().

In ceph_submit_write(), if ceph_inc_osd_stopping_blocker() fails -- which
happens during umount -- the request is aborted before submission: the
already-collected folios are only redirtied and unlocked, so
writepages_finish() never runs and the claim is leaked.
redirty_page_for_writepage() -> folio_redirty_for_writepage() ->
filemap_dirty_folio() sets PG_dirty directly and does not go through
->dirty_folio, so ceph_dirty_folio() is not re-entered to rebalance it.
Because every subsequent writeback also fails the osd_stopping_blocker,
i_wrbuffer_ref never returns to 0, the ihold() is never dropped, and the
inode cannot be evicted:

  VFS: Busy inodes after unmount of ceph
  kernel BUG at fs/super.c:650!

Release the orphaned claim in the abort path before redirtying, via
ceph_undo_wrbuffer_claim(): detach the snap_context, drop the wrbuffer
reference (letting i_wrbuffer_ref reach 0 and iput() the inode), and drop
the snap_context reference -- i.e. do what writepages_finish() would have
done for these never-submitted folios.

Only the locked_pages entries are undone; folios still in the fbatch were
never dirty-cleared by this call (folio_clear_dirty_for_io() is the
ownership-transfer point, and a successful move NULLs the fbatch slot), so
they hold no claim this call owns.

Cc: stable@vger.kernel.org
Fixes: fd7449d937 ("ceph: fix generic/421 test failure")
Signed-off-by: Matthew Brown <matthew@bargrove.com>
Reviewed-by: Xiubo Li <xiubo.li@clyso.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Matthew Brown 2026-08-12 18:13:21 +01:00 committed by Ilya Dryomov
parent 2a2f98e17e
commit c25aee9c63
1 changed files with 11 additions and 0 deletions
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11
fs/ceph/addr.c
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@ -1429,6 +1429,16 @@ void ceph_shift_unused_folios_left(struct folio_batch *fbatch)
fbatch->nr = n;
}
static void ceph_undo_wrbuffer_claim(struct inode *inode, struct folio *folio)
{
struct ceph_snap_context *snapc = folio_detach_private(folio);
if (!snapc)
return;
ceph_put_wrbuffer_cap_refs(ceph_inode(inode), 1, snapc);
ceph_put_snap_context(snapc);
}
static
int ceph_submit_write(struct address_space *mapping,
struct writeback_control *wbc,
@ -1492,6 +1502,7 @@ int ceph_submit_write(struct address_space *mapping,
if (!page)
continue;
ceph_undo_wrbuffer_claim(inode, page_folio(page));
redirty_page_for_writepage(wbc, page);
unlock_page(page);
}