bug#35475: Add filesystem flag NOATIME

bug#35475: Add filesystem flag NOATIME

[rendaw]

Package: guix
Version: 0.16.0
Severity: wishlist

This is useful for mounting drives with limited write lifetime such as
cheap ssds, and there have been some historical reports of noatime
causing COW-linked files on btrfs to split.

bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[rendaw]

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Add a no-atime flag to the file-system flags parameter and updates the
relevant documentation.

I believe these changes in the documentation give readers a starting
point for how to understand flags vs options, as well as indicate that
the reference is complete (that there isn't a separate reference with
more flags listed somewhere).



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From e7dcba4a76d624470d05172390dde8151fdb4750 Mon Sep 17 00:00:00 2001
From: rendaw <>
Date: Mon, 29 Apr 2019 01:00:17 +0900
Subject: [PATCH] [bug #35475] [PATCH] Add filesystem flag NOATIME

Add a no-atime flag to the file-system flags parameter and updates the relevant documentation.
---
 doc/guix.texi              | 11 +++++++----
 gnu/build/file-systems.scm |  2 ++
 guix/build/syscalls.scm    |  2 ++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 879cb562e9..8b89bdec53 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10726,13 +10726,16 @@ the system knows that mounting the file system depends on having the
 corresponding device mapping established.
 
 @item @code{flags} (default: @code{'()})
-This is a list of symbols denoting mount flags.  Recognized flags
-include @code{read-only}, @code{bind-mount}, @code{no-dev} (disallow
+This is a list of symbols denoting general mount flags.  Recognized flags
+are @code{read-only}, @code{bind-mount}, @code{no-dev} (disallow
 access to special files), @code{no-suid} (ignore setuid and setgid
-bits), and @code{no-exec} (disallow program execution.)
+bits), @code{no-exec} (disallow program execution), and @code{no-atime}.
+See @code{man 2 mount} for details.
 
 @item @code{options} (default: @code{#f})
-This is either @code{#f}, or a string denoting mount options.
+This is either @code{#f}, or a string denoting filesystem-specific mount
+options passed to the filesystem driver.  See @code{man 2 mount} for details
+and @code{man 8 mount} for options for various filesystems.
 
 @item @code{mount?} (default: @code{#t})
 This value indicates whether to automatically mount the file system when
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index c468144170..8bb10d574d 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -575,6 +575,8 @@ corresponds to the symbols listed in FLAGS."
        (logior MS_NODEV (loop rest)))
       (('no-exec rest ...)
        (logior MS_NOEXEC (loop rest)))
+      (('no-atime rest ...)
+       (logior MS_NOATIME (loop rest)))
       (()
        0))))
 
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 66d63a2931..3316dc8dc5 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -39,6 +39,7 @@
             MS_NODEV
             MS_NOEXEC
             MS_REMOUNT
+            MS_NOATIME
             MS_BIND
             MS_MOVE
             MS_STRICTATIME
@@ -451,6 +452,7 @@ the returned procedure is called."
 (define MS_NODEV              4)
 (define MS_NOEXEC             8)
 (define MS_REMOUNT           32)
+(define MS_NOATIME         1024)
 (define MS_BIND            4096)
 (define MS_MOVE            8192)
 (define MS_STRICTATIME 16777216)
-- 
2.21.0

bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[Ludovic Courtès]

Hello,

rendaw <7e9wc56emjakcm@s.rendaw.me> skribis:

> From e7dcba4a76d624470d05172390dde8151fdb4750 Mon Sep 17 00:00:00 2001
> From: rendaw <>
> Date: Mon, 29 Apr 2019 01:00:17 +0900
> Subject: [PATCH] [bug #35475] [PATCH] Add filesystem flag NOATIME
>
> Add a no-atime flag to the file-system flags parameter and updates the relevant documentation.
> ---
>  doc/guix.texi              | 11 +++++++----
>  gnu/build/file-systems.scm |  2 ++
>  guix/build/syscalls.scm    |  2 ++
>  3 files changed, 11 insertions(+), 4 deletions(-)

I tweaked the doc, added a commit log that follows our conventions¹, and
committed.

Thank you!

Ludo’.

¹ https://www.gnu.org/software/guix/manual/en/html_node/Submitting-Patches.html

bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[Danny Milosavljevic]

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Let's also add MS_RELATIME which is halfway between noatime and atime.

https://blog.confirm.ch/mount-options-atime-vs-relatime/

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bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[Ludovic Courtès]

Danny Milosavljevic <dannym@scratchpost.org> skribis:

> Let's also add MS_RELATIME which is halfway between noatime and atime.
>
> https://blog.confirm.ch/mount-options-atime-vs-relatime/

Good idea, could you send a patch?

Thanks,
Ludo’.

bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[rendaw]

On 4/29/19 7:14 PM, Ludovic Courtès wrote:
> Hello,
>
> rendaw <7e9wc56emjakcm@s.rendaw.me> skribis:
>
>> From e7dcba4a76d624470d05172390dde8151fdb4750 Mon Sep 17 00:00:00 2001
>> From: rendaw <>
>> Date: Mon, 29 Apr 2019 01:00:17 +0900
>> Subject: [PATCH] [bug #35475] [PATCH] Add filesystem flag NOATIME
>>
>> Add a no-atime flag to the file-system flags parameter and updates the relevant documentation.
>> ---
>>  doc/guix.texi              | 11 +++++++----
>>  gnu/build/file-systems.scm |  2 ++
>>  guix/build/syscalls.scm    |  2 ++
>>  3 files changed, 11 insertions(+), 4 deletions(-)
> I tweaked the doc, added a commit log that follows our conventions¹, and
> committed.
>
> Thank you!
>
> Ludo’.
>
> ¹ https://www.gnu.org/software/guix/manual/en/html_node/Submitting-Patches.html

Thank you!  And sorry, I'll read more carefully next time.

bug#35475: [bug #35475] [PATCH] Add filesystem flag NOATIME

[Ludovic Courtès]

rendaw <7e9wc56emjakcm@s.rendaw.me> skribis:

> On 4/29/19 7:14 PM, Ludovic Courtès wrote:

[...]

>> I tweaked the doc, added a commit log that follows our conventions¹, and
>> committed.
>>
>> Thank you!
>>
>> Ludo’.
>>
>> ¹ https://www.gnu.org/software/guix/manual/en/html_node/Submitting-Patches.html
>
> Thank you!  And sorry, I'll read more carefully next time.

Don’t be sorry, it’s perfectly understandable!

Ludo’.