On Thu, Aug 22, 2024 at 03:50:09PM +0200, Pankaj Raghav (Samsung) wrote: > 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> > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> > Tested-by: David Howells <dhowells@xxxxxxxxxx> > --- > include/linux/pagemap.h | 90 ++++++++++++++++++++++++++++++++++------- > mm/filemap.c | 6 +-- > mm/readahead.c | 4 +- > 3 files changed, 80 insertions(+), 20 deletions(-) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index d9c7edb6422bd..c60025bb584c5 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_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); This is my test case to be sure we don't overwrite flags: Before: AS_FOLIO_ORDER_MASK=0x1f AS_FOLIO_ORDER_MIN_MASK=0x1f0000 AS_FOLIO_ORDER_MAX_MASK=0x3e00000 v13: AS_FOLIO_ORDER_BITS_MASK=0x1f AS_FOLIO_ORDER_MASK=0x3ff0000 AS_FOLIO_ORDER_MIN_MASK=0x1f0000 AS_FOLIO_ORDER_MAX_MASK=0x3e00000 Test result for min=0, expected: min=0 Test result for min=0, expected: min=0 Test result for min=5, expected: min=5 Test result for min=10, expected: min=10 Test result for min=31, expected: min=31 Test result for min=31, expected: min=31 Test result for min=12, expected: min=12 Test result for min=20, expected: min=20 Test result for min=7, expected: min=7 Test result for min=14, expected: min=14 The test checks for flags in mapping_set_folio_order_range() and iterates over a list of test cases: flags = 0xffffffff _flags = flags & ~(AS_FOLIO_ORDER_MASK) newflags = _flags | (min_val << AS_FOLIO_ORDER_MIN) | (max_val << AS_FOLIO_ORDER_MAX) Reviewed-by: Daniel Gomez <da.gomez@xxxxxxxxxxx> > +} > + > +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) > diff --git a/mm/filemap.c b/mm/filemap.c > index d87c858465962..5c148144d5548 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1932,10 +1932,8 @@ 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 e83fe1c6e5acd..e0cf3bfd2b2b3 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -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() */ > -- > 2.44.1 >