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When a metadata buffer has to be copied out before it can be journalled, jbd2_journal_write_metadata_buffer() writes jh->b_frozen_data rather than the page cache copy. b_frozen_data is kmalloc()ed, so folio_set_bh() makes the shadow buffer point at a slab folio. That is not something the buffer_head layer can reason about. A slab folio overloads ->mapping, so a shadow buffer looks like it belongs to an address_space when it does not. buffer_set_crypto_ctx() already has to work around this, and it is the reason mark_buffer_write_io_error() cannot be called on a shadow buffer today. Point the shadow buffer at the frozen data itself instead: leave b_folio NULL, which it already is out of alloc_buffer_head(), and set b_data. The previous patch taught fs/buffer.c to submit such a buffer. folio_set_bh() is now needed on only one path - the one that journals the page cache copy directly - so it moves there, and new_folio, new_offset and the flag that used to pick between them all go away. The two commit-path checksum helpers reach the shadow buffer's contents through a new kmap_local_bh()/kunmap_local_bh() pair, which handle a buffer with or without a folio. Memory outside the page cache is always mapped, so for those there is nothing to map or unmap. Mapping it anyway would be worse than pointless: with CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP, kmap_local_page() hands back a one page mapping even for such memory, which is not enough for a buffer bigger than a page. Tested with ext4 mounted data=journal,journal_checksum on a metadata_csum filesystem, writing files whose every block begins with the JBD2 magic so that escaping forces the copy-out, then crashing with sysrq-b without unmounting and replaying the journal on the next mount. Recovery completed, the file contents matched, e2fsck -fn was clean, and an instrumented build confirmed the b_folio == NULL path was taken. Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Weidong Zhu <weizhu@fiu.edu> Signed-off-by: Chao Shi <coshi036@gmail.com> Link: https://patch.msgid.link/6140cd23beb88e99f40eaeff4044a16213f6caab.1785951556.git.coshi036@gmail.com Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org> |
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| clocksource | ||
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| hyperv | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
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| misc | ||
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| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
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| video | ||
| xen | ||
| Kbuild | ||