Commit 84429b67 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Christian Brauner
Browse files

fs: Allow fine-grained control of folio sizes 



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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Co-developed-by: default avatarPankaj Raghav <p.raghav@samsung.com>
Signed-off-by: default avatarPankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/r/20240822135018.1931258-2-kernel@pankajraghav.com


Tested-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDaniel Gomez <da.gomez@samsung.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 8400291e

include/linux/pagemap.h

+76 −14
Original line number Diff line number Diff line
@@ -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_INACCESSIBLE,	/* Do not attempt direct R/W access to the mapping,

				   including to move the mapping */

	AS_INACCESSIBLE = 8,	/* 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_BITS_MASK ((1u << AS_FOLIO_ORDER_BITS) - 1)

#define AS_FOLIO_ORDER_MIN_MASK (AS_FOLIO_ORDER_BITS_MASK << AS_FOLIO_ORDER_MIN)

#define AS_FOLIO_ORDER_MAX_MASK (AS_FOLIO_ORDER_BITS_MASK << AS_FOLIO_ORDER_MAX)

#define AS_FOLIO_ORDER_MASK (AS_FOLIO_ORDER_MIN_MASK | AS_FOLIO_ORDER_MAX_MASK)



/**

 * mapping_set_error - record a writeback error in the address_space

 * @mapping: the mapping in which an error should be set
@@ -367,9 +374,51 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask) 
#define MAX_XAS_ORDER		(XA_CHUNK_SHIFT * 2 - 1)

#define MAX_PAGECACHE_ORDER	min(MAX_XAS_ORDER, PREFERRED_MAX_PAGECACHE_ORDER)



/*

 * 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
@@ -380,7 +429,23 @@ 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;

}



/*
@@ -389,20 +454,17 @@ static inline void mapping_set_large_folios(struct address_space *mapping) 
 */

static inline bool mapping_large_folio_support(struct address_space *mapping)

{

	/* AS_LARGE_FOLIO_SUPPORT is only reasonable for pagecache folios */

	/* AS_FOLIO_ORDER is only reasonable for pagecache folios */

	VM_WARN_ONCE((unsigned long)mapping & PAGE_MAPPING_ANON,

			"Anonymous mapping always supports large folio");



	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)

mm/filemap.c

+2 −4
Original line number Diff line number Diff line
@@ -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);

mm/readahead.c

+2 −2
Original line number Diff line number Diff line
@@ -449,10 +449,10 @@ 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));



	/* See comment in page_cache_ra_unbounded() */