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Currently, the IsDCacheSizeOK check can trigger a false positive for a
dcache, if the data in the dcache was populated by a local write to a
file that was later extended with sparse data.
For example: say a client opens a new file, and writes 4 bytes to
offset 0, and then writes 4 bytes to offset 0x400000. After the first
write, the first chunk for the file will contain just 4 bytes, and
after the second write, the first chunk is unchanged (since we're
writing to a different area of the file), but the file is now 0x400004
bytes long. The sparse area of the file will be correctly filled with
zeroes for local reads and on the fileserver, but the 4-byte chunk
causes IsDCacheSizeOK to complain and mark the dcache as invalid.
Even though nothing is wrong, this causes the following scary messages
to potentially appear in the kernel log, and the relevant dcache to be
invalidated:
afs: Detected corrupt dcache for file 1.536870913.2.2: chunk 0 (offset 0) has 4 bytes, but it should have 131072 bytes
afs: (dcache 0xfffffdeadbeefb4d, file length 4194308, DV 1, dcache mtime 1575049956, index 996, dflags 0x2, mflags 0x0, states 0x4, vcache states 0x1)
afs: Ignoring the dcache for now, but this may indicate corruption in the AFS cache, or a bug.
It's probably difficult or impossible to detect if this specific case
is happening, so to avoid this scenario, just avoid doing the size
check at all for RW data from the cache.
Change-Id: Ia40ec838c525d9abc13a03be39028e4ca04a9457
Reviewed-on: https://gerrit.openafs.org/13969
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
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| doc | ||
| src | ||
| tests | ||
| .gitignore | ||
| .gitreview | ||
| .mailmap | ||
| .splintrc | ||
| acinclude.m4 | ||
| CODING | ||
| configure-libafs.ac | ||
| configure.ac | ||
| CONTRIBUTING | ||
| INSTALL | ||
| libafsdep | ||
| LICENSE | ||
| Makefile-libafs.in | ||
| Makefile.in | ||
| NEWS | ||
| NTMakefile | ||
| README | ||
| README-WINDOWS | ||
| regen.sh | ||
AFS is a distributed file system that enables users to share and access all of the files stored in a network of computers as easily as they access the files stored on their local machines. The file system is called distributed for this exact reason: files can reside on many different machines, but are available to users on every machine. OpenAFS 1.0 was originally released by IBM under the terms of the IBM Public License 1.0 (IPL10). For details on IPL10 see the LICENSE file in this directory. The current OpenAFS distribution is licensed under a combination of the IPL10 and many other licenses as granted by the relevant copyright holders. The LICENSE file in this directory contains more details, thought it is not a comprehensive statement. See INSTALL for information about building and installing OpenAFS on various platforms. See CODING for developer information and guidelines. See NEWS for recent changes to OpenAFS.