On 2022/04/19 18:17, David Howells <dhowells@xxxxxxxxxx> wrote: > find /var/cache/fscache -inum $((0xiiii)) > > and see if you can see the corruption in there. Note that there may be blocks > of zeroes corresponding to unfetched file blocks. I checked several known-corrupt files, but unfortunately, all corruption have disappeared :-( The /var/cache/fscache/ files have a time stamp half an hour ago (17:53 CET = 15:53 GMT). I don't know what happened at that time - too bad this disappeared after a week, just when we started investigating it. All those new files are all-zero. No data is stored in any of them. Note that I had to enable /sys/kernel/debug/tracing/events/cachefiles/enable; the trace events you named (read/write/trunc/io_error/vfs_error) do not emit anything. This is what I see: kworker/u98:11-1446185 [016] ..... 1813913.318370: cachefiles_ref: c=00014bd5 o=12080f1c u=1 NEW obj kworker/u98:11-1446185 [016] ..... 1813913.318379: cachefiles_lookup: o=12080f1c dB=3e01ee B=3e5580 e=0 kworker/u98:11-1446185 [016] ..... 1813913.318380: cachefiles_mark_active: o=12080f1c B=3e5580 kworker/u98:11-1446185 [016] ..... 1813913.318401: cachefiles_coherency: o=12080f1c OK B=3e5580 c=0 kworker/u98:11-1446185 [016] ..... 1813913.318402: cachefiles_ref: c=00014bd5 o=12080f1c u=1 SEE lookup_cookie > Also, what filesystem is backing your cachefiles cache? It could be useful to > dump the extent list of the file. You should be able to do this with > "filefrag -e". It's ext4. Filesystem type is: ef53 File size of /var/cache/fscache/cache/Infs,3.0,2,,a4214ac,c0000208,,,3002c0,10000,10000,12c,1770,bb8,1770,1/@58/T,c0000208,,1cf4167,184558d9,c0000208,,40,36bab37,40, is 188416 (46 blocks of 4096 bytes) /var/cache/fscache/cache/Infs,3.0,2,,a4214ac,c0000208,,,3002c0,10000,10000,12c,1770,bb8,1770,1/@58/T,c0000208,,1cf4167,184558d9,c0000208,,40,36bab37,40,: 0 extents found File size of /var/cache/fscache/cache/Infs,3.0,2,,a4214ac,c0000208,,,3002c0,10000,10000,12c,1770,bb8,1770,1/@ea/T,c0000208,,10cc976,1208c7f6,c0000208,,40,36bab37,40, is 114688 (28 blocks of 4096 bytes) /var/cache/fscache/cache/Infs,3.0,2,,a4214ac,c0000208,,,3002c0,10000,10000,12c,1770,bb8,1770,1/@ea/T,c0000208,,10cc976,1208c7f6,c0000208,,40,36bab37,40,: 0 extents found > As to why this happens, a write that's misaligned by 31 bytes should cause DIO > to a disk to fail - so it shouldn't be possible to write that. However, I'm > doing fallocate and truncate on the file to shape it so that DIO will work on > it, so it's possible that there's a bug there. The cachefiles_trunc trace > lines may help catch that. I don't think any write is misaligned. This was triggered by a WordPress update, so I think the WordPress updater truncated and rewrote all files. Random guess: some pages got transferred to the NFS server, but the local copy in fscache did not get updated. Max
