The patch titled
Subject: fsdax: use dax_page_idle() to document DAX busy page checking
has been added to the -mm mm-unstable branch. Its filename is
fsdax-use-dax_page_idle-to-document-dax-busy-page-checking.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fsdax-use-dax_page_idle-to-document-dax-busy-page-checking.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: fsdax: use dax_page_idle() to document DAX busy page checking
Date: Fri, 14 Oct 2022 16:57:08 -0700
In advance of converting DAX pages to be 0-based, use a new
dax_page_idle() helper to both simplify that future conversion, but also
document all the kernel locations that are watching for DAX page idle
events.
Link: https://lkml.kernel.org/r/166579182839.2236710.16461867548859813784.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
Cc: "Christian König" <christian.koenig@xxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Karol Herbst <kherbst@xxxxxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: "Pan, Xinhui" <Xinhui.Pan@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/dax.c | 4 ++--
fs/ext4/inode.c | 3 +--
fs/fuse/dax.c | 5 ++---
fs/xfs/xfs_file.c | 5 ++---
include/linux/dax.h | 9 +++++++++
5 files changed, 16 insertions(+), 10 deletions(-)
--- a/fs/dax.c~fsdax-use-dax_page_idle-to-document-dax-busy-page-checking
+++ a/fs/dax.c
@@ -395,7 +395,7 @@ static void dax_disassociate_entry(void
for_each_mapped_pfn(entry, pfn) {
struct page *page = pfn_to_page(pfn);
- WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
+ WARN_ON_ONCE(trunc && !dax_page_idle(page));
if (dax_mapping_is_cow(page->mapping)) {
/* keep the CoW flag if this page is still shared */
if (page->index-- > 0)
@@ -414,7 +414,7 @@ static struct page *dax_busy_page(void *
for_each_mapped_pfn(entry, pfn) {
struct page *page = pfn_to_page(pfn);
- if (page_ref_count(page) > 1)
+ if (!dax_page_idle(page))
return page;
}
return NULL;
--- a/fs/ext4/inode.c~fsdax-use-dax_page_idle-to-document-dax-busy-page-checking
+++ a/fs/ext4/inode.c
@@ -3968,8 +3968,7 @@ int ext4_break_layouts(struct inode *ino
if (!page)
return 0;
- error = ___wait_var_event(page,
- atomic_read(&page->_refcount) == 1,
+ error = ___wait_var_event(page, dax_page_idle(page),
TASK_INTERRUPTIBLE, 0, 0,
ext4_wait_dax_page(inode));
} while (error == 0);
--- a/fs/fuse/dax.c~fsdax-use-dax_page_idle-to-document-dax-busy-page-checking
+++ a/fs/fuse/dax.c
@@ -676,9 +676,8 @@ static int __fuse_dax_break_layouts(stru
return 0;
*retry = true;
- return ___wait_var_event(page, atomic_read(&page->_refcount) == 1,
- TASK_INTERRUPTIBLE, 0, 0,
- fuse_wait_dax_page(inode));
+ return ___wait_var_event(page, dax_page_idle(page), TASK_INTERRUPTIBLE,
+ 0, 0, fuse_wait_dax_page(inode));
}
/* dmap_end == 0 leads to unmapping of whole file */
--- a/fs/xfs/xfs_file.c~fsdax-use-dax_page_idle-to-document-dax-busy-page-checking
+++ a/fs/xfs/xfs_file.c
@@ -827,9 +827,8 @@ xfs_break_dax_layouts(
return 0;
*retry = true;
- return ___wait_var_event(page, atomic_read(&page->_refcount) == 1,
- TASK_INTERRUPTIBLE, 0, 0,
- xfs_wait_dax_page(inode));
+ return ___wait_var_event(page, dax_page_idle(page), TASK_INTERRUPTIBLE,
+ 0, 0, xfs_wait_dax_page(inode));
}
int
--- a/include/linux/dax.h~fsdax-use-dax_page_idle-to-document-dax-busy-page-checking
+++ a/include/linux/dax.h
@@ -210,6 +210,15 @@ int dax_zero_range(struct inode *inode,
int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
const struct iomap_ops *ops);
+/*
+ * Document all the code locations that want know when a dax page is
+ * unreferenced.
+ */
+static inline bool dax_page_idle(struct page *page)
+{
+ return page_ref_count(page) == 1;
+}
+
#if IS_ENABLED(CONFIG_DAX)
int dax_read_lock(void);
void dax_read_unlock(int id);
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
fsdax-wait-on-page-not-page-_refcount.patch
fsdax-use-dax_page_idle-to-document-dax-busy-page-checking.patch
fsdax-include-unmapped-inodes-for-page-idle-detection.patch
fsdax-introduce-dax_zap_mappings.patch
fsdax-wait-for-pinned-pages-during-truncate_inode_pages_final.patch
fsdax-validate-dax-layouts-broken-before-truncate.patch
fsdax-hold-dax-lock-over-mapping-insertion.patch
fsdax-update-dax_insert_entry-calling-convention-to-return-an-error.patch
fsdax-rework-for_each_mapped_pfn-to-dax_for_each_folio.patch
fsdax-introduce-pgmap_request_folios.patch
fsdax-rework-dax_insert_entry-calling-convention.patch
fsdax-cleanup-dax_associate_entry.patch
devdax-minor-warning-fixups.patch
devdax-fix-sparse-lock-imbalance-warning.patch
libnvdimm-pmem-support-pmem-block-devices-without-dax.patch
devdax-move-address_space-helpers-to-the-dax-core.patch
devdax-sparse-fixes-for-xarray-locking.patch
devdax-sparse-fixes-for-vmfault_t-dax-entry-conversions.patch
devdax-sparse-fixes-for-vm_fault_t-in-tracepoints.patch
devdax-add-pud-support-to-the-dax-mapping-infrastructure.patch
devdax-use-dax_insert_entry-dax_delete_mapping_entry.patch
mm-memremap_pages-replace-zone_device_page_init-with-pgmap_request_folios.patch
mm-memremap_pages-initialize-all-zone_device-pages-to-start-at-refcount-0.patch
mm-meremap_pages-delete-put_devmap_managed_page_refs.patch
mm-gup-drop-dax-pgmap-accounting.patch
