diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/asm-annotations.rst | 2 | ||||
| -rw-r--r-- | Documentation/core-api/dma-api-howto.rst | 2 | ||||
| -rw-r--r-- | Documentation/core-api/pin_user_pages.rst | 31 |
3 files changed, 17 insertions, 18 deletions
diff --git a/Documentation/core-api/asm-annotations.rst b/Documentation/core-api/asm-annotations.rst index bc514ed59887..11c96d3f9ad6 100644 --- a/Documentation/core-api/asm-annotations.rst +++ b/Documentation/core-api/asm-annotations.rst @@ -44,7 +44,7 @@ information. In particular, on properly annotated objects, ``objtool`` can be run to check and fix the object if needed. Currently, ``objtool`` can report missing frame pointer setup/destruction in functions. It can also automatically generate annotations for the ORC unwinder -(Documentation/x86/orc-unwinder.rst) +(Documentation/arch/x86/orc-unwinder.rst) for most code. Both of these are especially important to support reliable stack traces which are in turn necessary for kernel live patching (Documentation/livepatch/livepatch.rst). diff --git a/Documentation/core-api/dma-api-howto.rst b/Documentation/core-api/dma-api-howto.rst index 828846804e25..72f6cdb6be1c 100644 --- a/Documentation/core-api/dma-api-howto.rst +++ b/Documentation/core-api/dma-api-howto.rst @@ -185,7 +185,7 @@ device struct of your device is embedded in the bus-specific device struct of your device. For example, &pdev->dev is a pointer to the device struct of a PCI device (pdev is a pointer to the PCI device struct of your device). -These calls usually return zero to indicated your device can perform DMA +These calls usually return zero to indicate your device can perform DMA properly on the machine given the address mask you provided, but they might return an error if the mask is too small to be supportable on the given system. If it returns non-zero, your device cannot perform DMA properly on diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core-api/pin_user_pages.rst index b18416f4500f..9fb0b1080d3b 100644 --- a/Documentation/core-api/pin_user_pages.rst +++ b/Documentation/core-api/pin_user_pages.rst @@ -55,18 +55,17 @@ flags the caller provides. The caller is required to pass in a non-null struct pages* array, and the function then pins pages by incrementing each by a special value: GUP_PIN_COUNTING_BIAS. -For compound pages, the GUP_PIN_COUNTING_BIAS scheme is not used. Instead, -an exact form of pin counting is achieved, by using the 2nd struct page -in the compound page. A new struct page field, compound_pincount, has -been added in order to support this. - -This approach for compound pages avoids the counting upper limit problems that -are discussed below. Those limitations would have been aggravated severely by -huge pages, because each tail page adds a refcount to the head page. And in -fact, testing revealed that, without a separate compound_pincount field, -page overflows were seen in some huge page stress tests. - -This also means that huge pages and compound pages do not suffer +For large folios, the GUP_PIN_COUNTING_BIAS scheme is not used. Instead, +the extra space available in the struct folio is used to store the +pincount directly. + +This approach for large folios avoids the counting upper limit problems +that are discussed below. Those limitations would have been aggravated +severely by huge pages, because each tail page adds a refcount to the +head page. And in fact, testing revealed that, without a separate pincount +field, refcount overflows were seen in some huge page stress tests. + +This also means that huge pages and large folios do not suffer from the false positives problem that is mentioned below.:: Function @@ -221,7 +220,7 @@ Unit testing ============ This file:: - tools/testing/selftests/vm/gup_test.c + tools/testing/selftests/mm/gup_test.c has the following new calls to exercise the new pin*() wrapper functions: @@ -264,9 +263,9 @@ place.) Other diagnostics ================= -dump_page() has been enhanced slightly, to handle these new counting -fields, and to better report on compound pages in general. Specifically, -for compound pages, the exact (compound_pincount) pincount is reported. +dump_page() has been enhanced slightly to handle these new counting +fields, and to better report on large folios in general. Specifically, +for large folios, the exact pincount is reported. References ========== |