[PATCH v7 02/11] fs: Allow fine-grained control of folio sizes
From: Pankaj Raghav (Samsung)
Date: Fri Jun 07 2024 - 11:01:30 EST
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
We need filesystems to be able to communicate acceptable folio sizes
to the pagecache for a variety of uses (e.g. large block sizes).
Support a range of folio sizes between order-0 and order-31.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Co-developed-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
---
include/linux/pagemap.h | 86 ++++++++++++++++++++++++++++++++++-------
mm/filemap.c | 6 +--
mm/readahead.c | 4 +-
3 files changed, 77 insertions(+), 19 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 8f09ed4a4451..228275e7049f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -204,14 +204,21 @@ enum mapping_flags {
AS_EXITING = 4, /* final truncate in progress */
/* writeback related tags are not used */
AS_NO_WRITEBACK_TAGS = 5,
- AS_LARGE_FOLIO_SUPPORT = 6,
- AS_RELEASE_ALWAYS, /* Call ->release_folio(), even if no private data */
- AS_STABLE_WRITES, /* must wait for writeback before modifying
+ AS_RELEASE_ALWAYS = 6, /* Call ->release_folio(), even if no private data */
+ AS_STABLE_WRITES = 7, /* must wait for writeback before modifying
folio contents */
- AS_UNMOVABLE, /* The mapping cannot be moved, ever */
- AS_INACCESSIBLE, /* Do not attempt direct R/W access to the mapping */
+ AS_UNMOVABLE = 8, /* The mapping cannot be moved, ever */
+ AS_INACCESSIBLE = 9, /* Do not attempt direct R/W access to the mapping */
+ /* Bits 16-25 are used for FOLIO_ORDER */
+ AS_FOLIO_ORDER_BITS = 5,
+ AS_FOLIO_ORDER_MIN = 16,
+ AS_FOLIO_ORDER_MAX = AS_FOLIO_ORDER_MIN + AS_FOLIO_ORDER_BITS,
};
+#define AS_FOLIO_ORDER_MASK ((1u << AS_FOLIO_ORDER_BITS) - 1)
+#define AS_FOLIO_ORDER_MIN_MASK (AS_FOLIO_ORDER_MASK << AS_FOLIO_ORDER_MIN)
+#define AS_FOLIO_ORDER_MAX_MASK (AS_FOLIO_ORDER_MASK << AS_FOLIO_ORDER_MAX)
+
/**
* mapping_set_error - record a writeback error in the address_space
* @mapping: the mapping in which an error should be set
@@ -360,9 +367,49 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
#define MAX_PAGECACHE_ORDER 8
#endif
+/*
+ * mapping_set_folio_order_range() - Set the orders supported by a file.
+ * @mapping: The address space of the file.
+ * @min: Minimum folio order (between 0-MAX_PAGECACHE_ORDER inclusive).
+ * @max: Maximum folio order (between @min-MAX_PAGECACHE_ORDER inclusive).
+ *
+ * The filesystem should call this function in its inode constructor to
+ * indicate which base size (min) and maximum size (max) of folio the VFS
+ * can use to cache the contents of the file. This should only be used
+ * if the filesystem needs special handling of folio sizes (ie there is
+ * something the core cannot know).
+ * Do not tune it based on, eg, i_size.
+ *
+ * Context: This should not be called while the inode is active as it
+ * is non-atomic.
+ */
+static inline void mapping_set_folio_order_range(struct address_space *mapping,
+ unsigned int min,
+ unsigned int max)
+{
+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+ return;
+
+ if (min > MAX_PAGECACHE_ORDER)
+ min = MAX_PAGECACHE_ORDER;
+ if (max > MAX_PAGECACHE_ORDER)
+ max = MAX_PAGECACHE_ORDER;
+ if (max < min)
+ max = min;
+
+ mapping->flags = (mapping->flags & ~AS_FOLIO_ORDER_MASK) |
+ (min << AS_FOLIO_ORDER_MIN) | (max << AS_FOLIO_ORDER_MAX);
+}
+
+static inline void mapping_set_folio_min_order(struct address_space *mapping,
+ unsigned int min)
+{
+ mapping_set_folio_order_range(mapping, min, MAX_PAGECACHE_ORDER);
+}
+
/**
* mapping_set_large_folios() - Indicate the file supports large folios.
- * @mapping: The file.
+ * @mapping: The address space of the file.
*
* The filesystem should call this function in its inode constructor to
* indicate that the VFS can use large folios to cache the contents of
@@ -373,7 +420,23 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
*/
static inline void mapping_set_large_folios(struct address_space *mapping)
{
- __set_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
+ mapping_set_folio_order_range(mapping, 0, MAX_PAGECACHE_ORDER);
+}
+
+static inline
+unsigned int mapping_max_folio_order(const struct address_space *mapping)
+{
+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+ return 0;
+ return (mapping->flags & AS_FOLIO_ORDER_MAX_MASK) >> AS_FOLIO_ORDER_MAX;
+}
+
+static inline
+unsigned int mapping_min_folio_order(const struct address_space *mapping)
+{
+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+ return 0;
+ return (mapping->flags & AS_FOLIO_ORDER_MIN_MASK) >> AS_FOLIO_ORDER_MIN;
}
/*
@@ -382,16 +445,13 @@ static inline void mapping_set_large_folios(struct address_space *mapping)
*/
static inline bool mapping_large_folio_support(struct address_space *mapping)
{
- return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
- test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
+ return mapping_max_folio_order(mapping) > 0;
}
/* Return the maximum folio size for this pagecache mapping, in bytes. */
-static inline size_t mapping_max_folio_size(struct address_space *mapping)
+static inline size_t mapping_max_folio_size(const struct address_space *mapping)
{
- if (mapping_large_folio_support(mapping))
- return PAGE_SIZE << MAX_PAGECACHE_ORDER;
- return PAGE_SIZE;
+ return PAGE_SIZE << mapping_max_folio_order(mapping);
}
static inline int filemap_nr_thps(struct address_space *mapping)
diff --git a/mm/filemap.c b/mm/filemap.c
index 37061aafd191..46c7a6f59788 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1933,10 +1933,8 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
fgp_flags |= FGP_LOCK;
- if (!mapping_large_folio_support(mapping))
- order = 0;
- if (order > MAX_PAGECACHE_ORDER)
- order = MAX_PAGECACHE_ORDER;
+ if (order > mapping_max_folio_order(mapping))
+ order = mapping_max_folio_order(mapping);
/* If we're not aligned, allocate a smaller folio */
if (index & ((1UL << order) - 1))
order = __ffs(index);
diff --git a/mm/readahead.c b/mm/readahead.c
index 75e934a1fd78..da34b28da02c 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -504,9 +504,9 @@ void page_cache_ra_order(struct readahead_control *ractl,
limit = min(limit, index + ra->size - 1);
- if (new_order < MAX_PAGECACHE_ORDER) {
+ if (new_order < mapping_max_folio_order(mapping)) {
new_order += 2;
- new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order);
+ new_order = min(mapping_max_folio_order(mapping), new_order);
new_order = min_t(unsigned int, new_order, ilog2(ra->size));
}
--
2.44.1