linux-kernel - [PATCH RESEND v5] XArray: minor documentation improvements

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Message-Id: <20241105-xarray-documentation-v5-1-8e1702321b41@gmail.com>
Date: Tue, 05 Nov 2024 08:03:42 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Matthew Wilcox <willy@...radead.org>, Jonathan Corbet <corbet@....net>
Cc: linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>, 
 Bagas Sanjaya <bagasdotme@...il.com>, Tamir Duberstein <tamird@...il.com>
Subject: [PATCH RESEND v5] XArray: minor documentation improvements

- Replace "they" with "you" where "you" is used in the preceding
  sentence fragment.
- Mention `xa_erase` in discussion of multi-index entries.  Split this
  into a separate sentence.
- Add "call" parentheses on "xa_store" for consistency and
  linkification.
- Add caveat that `xa_store` and `xa_erase` are not equivalent in the
  presence of `XA_FLAGS_ALLOC`.

Acked-by: Randy Dunlap <rdunlap@...radead.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@...il.com>
Signed-off-by: Tamir Duberstein <tamird@...il.com>
---
Changes in v5:
- Add trailers; otherwise resend of v4. Sent as v5 due to tooling issue.
- Link to v4: https://lore.kernel.org/r/20241010214150.52895-2-tamird@gmail.com/

Changes in v4:
- Remove latent sentence fragment.

Changes in v3:
- metion `xa_erase`/`xa_store(NULL)` in multi-index entry discussion.
- mention non-equivalent of `xa_erase`/`xa_store(NULL)` in the presence
  of `XA_FLAGS_ALLOC`.

Changes in v2:
- s/use/you/ (Darrick J. Wong)
---
 Documentation/core-api/xarray.rst | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst
index 77e0ece2b1d6f8e632e7d28d17fd1c60fcf0b5c4..f6a3eef4fe7f0a84068048175cb857d566f63516 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -42,8 +42,8 @@ call xa_tag_pointer() to create an entry with a tag, xa_untag_pointer()
 to turn a tagged entry back into an untagged pointer and xa_pointer_tag()
 to retrieve the tag of an entry.  Tagged pointers use the same bits that
 are used to distinguish value entries from normal pointers, so you must
-decide whether they want to store value entries or tagged pointers in
-any particular XArray.
+decide whether you want to store value entries or tagged pointers in any
+particular XArray.
 
 The XArray does not support storing IS_ERR() pointers as some
 conflict with value entries or internal entries.
@@ -52,8 +52,9 @@ An unusual feature of the XArray is the ability to create entries which
 occupy a range of indices.  Once stored to, looking up any index in
 the range will return the same entry as looking up any other index in
 the range.  Storing to any index will store to all of them.  Multi-index
-entries can be explicitly split into smaller entries, or storing ``NULL``
-into any entry will cause the XArray to forget about the range.
+entries can be explicitly split into smaller entries. Unsetting (using
+xa_erase() or xa_store() with ``NULL``) any entry will cause the XArray
+to forget about the range.
 
 Normal API
 ==========
@@ -63,13 +64,14 @@ for statically allocated XArrays or xa_init() for dynamically
 allocated ones.  A freshly-initialised XArray contains a ``NULL``
 pointer at every index.
 
-You can then set entries using xa_store() and get entries
-using xa_load().  xa_store will overwrite any entry with the
-new entry and return the previous entry stored at that index.  You can
-use xa_erase() instead of calling xa_store() with a
-``NULL`` entry.  There is no difference between an entry that has never
-been stored to, one that has been erased and one that has most recently
-had ``NULL`` stored to it.
+You can then set entries using xa_store() and get entries using
+xa_load().  xa_store() will overwrite any entry with the new entry and
+return the previous entry stored at that index.  You can unset entries
+using xa_erase() or by setting the entry to ``NULL`` using xa_store().
+There is no difference between an entry that has never been stored to
+and one that has been erased with xa_erase(); an entry that has most
+recently had ``NULL`` stored to it is also equivalent except if the
+XArray was initialized with ``XA_FLAGS_ALLOC``.
 
 You can conditionally replace an entry at an index by using
 xa_cmpxchg().  Like cmpxchg(), it will only succeed if

---
base-commit: 850925a8133c73c4a2453c360b2c3beb3bab67c9
change-id: 20241026-xarray-documentation-86e1f2d047db

Best regards,
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-- 
Tamir Duberstein <tamird@...il.com>