linux-kernel - Re: [PATCH 3/3] iomap: rework IOMAP atomic flags

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Message-ID: <87bjtrsw2d.fsf@gmail.com>
Date: Sun, 23 Mar 2025 19:12:02 +0530
From: Ritesh Harjani (IBM) <ritesh.list@...il.com>
To: Christoph Hellwig <hch@....de>
Cc: John Garry <john.g.garry@...cle.com>, brauner@...nel.org, djwong@...nel.org, hch@....de, linux-fsdevel@...r.kernel.org, dchinner@...hat.com, linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com, martin.petersen@...cle.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 3/3] iomap: rework IOMAP atomic flags

Christoph Hellwig <hch@....de> writes:

> On Sun, Mar 23, 2025 at 01:17:08AM +0530, Ritesh Harjani wrote:
>
> [full quote deleted, can you please properly trim your replies?]
>

Sure.

>> So, I guess we can shift IOMAP_F_SIZE_CHANGED and IOMAP_F_STALE by
>> 1 bit. So it will all look like.. 
>
> Let's create some more space to avoid this for the next round, e.g.

Sure, that make sense. 

> count the core set flags from 31 down, and limit IOMAP_F_PRIVATE to a
> single flag, which is how it is used.

flags in struct iomap is of type u16. So will make core iomap flags
starting from bit 15, moving downwards. 

Here is a diff of what I think you meant - let me know if this diff
looks good to you? 



diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 02fe001feebb..68416b135151 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -78,6 +78,11 @@ struct vm_fault;
 #define IOMAP_F_ANON_WRITE     (1U << 7)
 #define IOMAP_F_ATOMIC_BIO     (1U << 8)

+/*
+ * Flag reserved for file system specific usage
+ */
+#define IOMAP_F_PRIVATE                (1U << 12)
+
 /*
  * Flags set by the core iomap code during operations:
  *
@@ -88,14 +93,8 @@ struct vm_fault;
  * range it covers needs to be remapped by the high level before the operation
  * can proceed.
  */
-#define IOMAP_F_SIZE_CHANGED   (1U << 8)
-#define IOMAP_F_STALE          (1U << 9)
-
-/*
- * Flags from 0x1000 up are for file system specific usage:
- */
-#define IOMAP_F_PRIVATE                (1U << 12)
-
+#define IOMAP_F_SIZE_CHANGED   (1U << 14)
+#define IOMAP_F_STALE          (1U << 15)

 /*
  * Magic value for addr:



(PS: I might be on transit / travel for some other work for a week. My reponses may be delayed.)
-ritesh