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qm: virtiofs: drop writeback cache

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VirtIO-fs using writeback cache seems very broken at the moment. If a
guest accesses a file (even just using 'touch'), that the host is
currently writing, the guest can permanently end up with a truncated
version of that file. Even subsequent operations like moving the file,
will not result in the correct file being visible, but just rename the
truncated one.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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Fiona Ebner 2025-04-08 17:07:15 +02:00 committed by Thomas Lamprecht
parent 9afbde533d
commit 23123df035
1 changed files with 2 additions and 2 deletions
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@ -1309,7 +1309,7 @@ has been configured in the resource mapping. Additionally, you can set the
`cache` option to either `always`, `never`, `metadata`, or `auto` (default:
`auto`), depending on your requirements. How the different caching modes behave
can be read https://lwn.net/Articles/774495/[here under the "Caching Modes"
section]. To enable writeback cache set `writeback` to `1`.
section].
The `virtiofsd` supports ACL and xattr passthrough (can be enabled with the
`expose-acl` and `expose-xattr` options), allowing the guest to access ACLs and
@ -1327,7 +1327,7 @@ applications do their own caching.
----
qm set <vmid> -virtiofs0 dirid=<dirid>,cache=always,direct-io=1
qm set <vmid> -virtiofs1 <dirid>,cache=never,expose-xattr=1
qm set <vmid> -virtiofs2 <dirid>,expose-acl=1,writeback=1
qm set <vmid> -virtiofs2 <dirid>,expose-acl=1
----
To temporarily mount virtiofs in a guest VM with the Linux kernel virtiofs