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Filename Latest commit message Latest commit date
Nikos Tsironis fb89863630 dm era: Reinitialize bitset cache before digesting a new writeset
commit 2524933307fd0036d5c32357c693c021ab09a0b0 upstream.

In case of devices with at most 64 blocks, the digestion of consecutive
eras uses the writeset of the first era as the writeset of all eras to
digest, leading to lost writes. That is, we lose the information about
what blocks were written during the affected eras.

The digestion code uses a dm_disk_bitset object to access the archived
writesets. This structure includes a one word (64-bit) cache to reduce
the number of array lookups.

This structure is initialized only once, in metadata_digest_start(),
when we kick off digestion.

But, when we insert a new writeset into the writeset tree, before the
digestion of the previous writeset is done, or equivalently when there
are multiple writesets in the writeset tree to digest, then all these
writesets are digested using the same cache and the cache is not
re-initialized when moving from one writeset to the next.

For devices with more than 64 blocks, i.e., the size of the cache, the
cache is indirectly invalidated when we move to a next set of blocks, so
we avoid the bug.

But for devices with at most 64 blocks we end up using the same cached
data for digesting all archived writesets, i.e., the cache is loaded
when digesting the first writeset and it never gets reloaded, until the
digestion is done.

As a result, the writeset of the first era to digest is used as the
writeset of all the following archived eras, leading to lost writes.

Fix this by reinitializing the dm_disk_bitset structure, and thus
invalidating the cache, every time the digestion code starts digesting a
new writeset.

Fixes: eec40579d8 ("dm: add era target")
Cc: stable@vger.kernel.org # v3.15+
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04 10:26:52 +01:00
arch sparc32: fix a user-triggerable oops in clear_user() 2021-03-04 10:26:50 +01:00
block blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 10:26:40 +01:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: ecdh_helper - Ensure 'len >= secret.len' in decode_key() 2021-03-04 10:26:25 +01:00
Documentation seq_file: document how per-entry resources are managed. 2021-03-04 10:26:48 +01:00
drivers dm era: Reinitialize bitset cache before digesting a new writeset 2021-03-04 10:26:52 +01:00
fs gfs2: Recursive gfs2_quota_hold in gfs2_iomap_end 2021-03-04 10:26:51 +01:00
include dm: fix deadlock when swapping to encrypted device 2021-03-04 10:26:51 +01:00
init fgraph: Initialize tracing_graph_pause at task creation 2021-02-10 09:25:29 +01:00
ipc
kernel printk: fix deadlock when kernel panic 2021-03-04 10:26:50 +01:00
lib udp: fix skb_copy_and_csum_datagram with odd segment sizes 2021-02-17 10:35:19 +01:00
LICENSES
mm hugetlb: fix copy_huge_page_from_user contig page struct assumption 2021-03-04 10:26:49 +01:00
net bpf: Fix bpf_fib_lookup helper MTU check for SKB ctx 2021-03-04 10:26:17 +01:00
samples
scripts scripts/recordmcount.pl: support big endian for ARCH sh 2021-02-26 10:10:28 +01:00
security KEYS: trusted: Fix migratable=1 failing 2021-03-04 10:26:44 +01:00
sound ALSA: hda/realtek: modify EAPD in the ALC886 2021-03-04 10:26:42 +01:00
tools perf test: Fix unaligned access in sample parsing test 2021-03-04 10:26:35 +01:00
usr
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-02-26 10:10:28 +01:00
.clang-format
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Makefile Linux 5.4.101 2021-02-26 10:10:28 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.