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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) MIME-Version: 1.0 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B752940008 X-Stat-Signature: ysfm1a46opn5z1eakua4wpsqzst41aph X-Rspam-User: X-HE-Tag: 1743300357-28397 X-HE-Meta: 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 kELN+pcP 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 2025-03-27 at 14:42 -0700, Luis Chamberlain wrote: > On Thu, Mar 27, 2025 at 09:26:41AM -0700, syzbot wrote: > > Hello, >=20 > Thanks, this is a known issue and we're having a hard time > reproducing [0]. >=20 > > C reproducer:=C2=A0=C2=A0 > > https://syzkaller.appspot.com/x/repro.c?x=3D152d4de4580000 >=20 > Thanks! Sadly this has not yet been able to let me reprodouce the > issue, > and so we're trying to come up with other ways to test the imminent > spin > lock + sleep on buffer_migrate_folio_norefs() path different ways > now, > including a new fstests [1] but no luck yet. The backtrace in the report seems to make the cause of the bug fairly clear, though. The function folio_mc_copy() can sleep. The function __buffer_migrate_folio() calls filemap_migrate_folio() with a spinlock held. That function eventually calls folio_mc_copy(): __might_resched+0x5d4/0x780 kernel/sched/core.c:8764 folio_mc_copy+0x13c/0x1d0 mm/util.c:742 __migrate_folio mm/migrate.c:758 [inline] filemap_migrate_folio+0xb4/0x4c0 mm/migrate.c:943 __buffer_migrate_folio+0x3ec/0x5d0 mm/migrate.c:874 move_to_new_folio+0x2ac/0xc20 mm/migrate.c:1050 migrate_folio_move mm/migrate.c:1358 [inline] migrate_folios_move mm/migrate.c:1710 [inline] The big question is how to safely release the spinlock in __buffer_migrate_folio() before calling filemap_migrate_folio() --=20 All Rights Reversed.