diff options
| author | Davidlohr Bueso <dave@stgolabs.net> | 2025-04-17 18:59:21 -0700 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-04-22 18:16:08 +0200 |
| commit | 2d900efff915fe24c3948d28eef9078953d87fec (patch) | |
| tree | 1ec506089a27903c16eb743dcd238290518261ea /mm | |
| parent | 6e8f57fd09c9fb569d10b2ccc3878155b702591a (diff) | |
mm/migrate: fix sleep in atomic for large folios and buffer heads
The large folio + buffer head noref migration scenarios are
being naughty and blocking while holding a spinlock.
As a consequence of the pagecache lookup path taking the
folio lock this serializes against migration paths, so
they can wait for each other. For the private_lock
atomic case, a new BH_Migrate flag is introduced which
enables the lookup to bail.
This allows the critical region of the private_lock on
the migration path to be reduced to the way it was before
ebdf4de5642fb6 ("mm: migrate: fix reference check race
between __find_get_block() and migration"), that is covering
the count checks.
The scope is always noref migration.
Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: syzbot+f3c6fda1297c748a7076@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/oe-lkp/202503101536.27099c77-lkp@intel.com
Fixes: 3c20917120ce61 ("block/bdev: enable large folio support for large logical block sizes")
Reviewed-by: Jan Kara <jack@suse.cz>
Co-developed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://kdevops.org/ext4/v6.15-rc2.html # [0]
Link: https://lore.kernel.org/all/aAAEvcrmREWa1SKF@bombadil.infradead.org/ # [1]
Link: https://lore.kernel.org/20250418015921.132400-8-dave@stgolabs.net
Tested-by: kdevops@lists.linux.dev # [0] [1]
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/migrate.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index f3ee6d8d5e2e..676d9cfc7059 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -845,9 +845,11 @@ static int __buffer_migrate_folio(struct address_space *mapping, return -EAGAIN; if (check_refs) { - bool busy; + bool busy, migrating; bool invalidated = false; + migrating = test_and_set_bit_lock(BH_Migrate, &head->b_state); + VM_WARN_ON_ONCE(migrating); recheck_buffers: busy = false; spin_lock(&mapping->i_private_lock); @@ -859,12 +861,12 @@ recheck_buffers: } bh = bh->b_this_page; } while (bh != head); + spin_unlock(&mapping->i_private_lock); if (busy) { if (invalidated) { rc = -EAGAIN; goto unlock_buffers; } - spin_unlock(&mapping->i_private_lock); invalidate_bh_lrus(); invalidated = true; goto recheck_buffers; @@ -883,7 +885,7 @@ recheck_buffers: unlock_buffers: if (check_refs) - spin_unlock(&mapping->i_private_lock); + clear_bit_unlock(BH_Migrate, &head->b_state); bh = head; do { unlock_buffer(bh); |