@osandov you already made it to Phoronix.
https://www.phoronix.com/news/Linux-6.14-Faster-kcore-Reads
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util-linux has merged support for statmount() and listmount() to list mounts:
https://github.com/util-linux/util-linux/pull/3092#event-15865684400
This should be a nice performance improvement.
See https://brauner.io/2024/12/16/list-all-mounts.html for some details on listmount() and statmount().
[#]linux #kernel
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I'm organizing the #containers and #kernel devrooms at FOSDEM 2025 with the usual suspects.
containers: https://fosdem.org/2025/schedule/track/containers
kernel: https://fosdem.org/2025/schedule/track/kernel
See you in Brussels!
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I've written a post that shows how to list all mounts in all mount namespaces (all mounts on the system) using new apis we added to the #vfs this year.
https://brauner.io/2024/12/16/list-all-mounts.html
[#]kernel #linux #vfs
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How do people test 32bit #kernels today? What is an easy way to build a 32bit kernel and userspace?
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After searching for quite a while and no clear answer here's a question for the perf bubble. I have a multi-threaded test program and I want a kernel callgraph that shows me the overhead or percentage of each function in the callgraph (aggregated over all threads, I guess). The goal is to identify changes caused by various patches.
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The thing I often need the most but don't have is a private test machine with as many cpus as possible so I can do meaningful performance testing. For example, right now I want to test some refcount improvements but I lack a machine with enough cpus to do that which is really annoying.
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Is https://cybersecuritynews.com/critical-unauthenticated-rce-flaw/ kernel or userspace?
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I'm excited for @jann's CONFIG_SLUB_RCU_DEBUG which has just landed. This will make it easier to detect UAF with struct file that relies on SLAB_TYPESAFE_BY_RCU.
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I just realized that I sent 7 pull requests on Friday, 13th to @torvalds. Literally the second I sent the last one.
Should... should I be worried?
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https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf
"99) If the member used to read the contents of a union object is not the same as the member last used to store a value in the
object, the appropriate part of the object representation of the value is reinterpreted as an object representation in the new
type as described in 6.2.6 (a process sometimes called "type punning"). This might be a trap representation."
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I think I might've annoyed @arnd already with that question before?
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IOW, if I did:
struct foo meh = {
.nr_entries = 1234,
.p = some_array;
.q = some_other_array;
};
can I rely on that no being undefined behavior. I think C11 guarantees this type punning.
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Basically my questions comes down to whether in an anoymous union like:
struct foo {
union {
struct {
struct bar b[5]; /* 60 bytes */
u32 nr_entries;
};
struct {
void *p;
void *q;
};
};
};I can use nr_entries to index p/q and b.
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Why on earth do they want me to pay CHF 216 for the C standard https://www.iso.org/standard/74528.html
Is there a free version of this? And isn't this weird that a lot of OSS is written in C but the standard is behind a big fat paywall?
I just have question about unions...
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@vbabka sent v4 https://lore.kernel.org/r/20240905-work-kmem_cache_args-v4-0-ed45d5380679@kernel.org allowing NULL to mean "default value".
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I wonder if @vbabka is already starting to regret the kmem_cache_create() refactor. :D
v2 just went out. I hope I don't have him screaming. ;)
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How do people deal with non-ASCII characters in To: and Cc: fields in mails they send via git send-email?
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Series sent https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-0-6d3e4816aa7b@kernel.org we'll see if that holds up.
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I can probably mange to free up another 8 bytes in struct file by killing f_version and moving it into the few filesystems that care about it.
That would give us back 8 bytes for future expansions.
It's a rough draft and lacking commit messages but it should work (famous last words)...
https://github.com/brauner/linux/commits/vfs.file.f_version
[#]linux #kernel
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