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Current metadata buffer release logic in bdev_try_to_free_page() have a lot of use-after-free issues when umount filesystem concurrently, and it is difficult to fix directly because ext4 is the only user of s_op->bdev_try_to_free_page callback and we may have to add more special refcount or lock that is only used by ext4 into the common vfs layer, which is unacceptable. One better solution is remove the bdev_try_to_free_page callback, but the real problem is we cannot easily release journal_head on the checkpointed buffer, so try_to_free_buffers() cannot release buffers and page under memory pressure, which is more likely to trigger out-of-memory. So we cannot remove the callback directly before we find another way to release journal_head. This patch introduce a shrinker to free journal_head on the checkpointed transaction. After the journal_head got freed, try_to_free_buffers() could free buffer properly. Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Suggested-by: Jan Kara <jack@suse.cz> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210610112440.3438139-6-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
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| .. | ||
| checkpoint.c | ||
| commit.c | ||
| journal.c | ||
| Kconfig | ||
| Makefile | ||
| recovery.c | ||
| revoke.c | ||
| transaction.c | ||