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readahead: allocate folios with mapping_min_order in readahead

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page_cache_ra_unbounded() was allocating single pages (0 order folios)
if there was no folio found in an index. Allocate mapping_min_order folios
as we need to guarantee the minimum order if it is set.

page_cache_ra_order() tries to allocate folio to the page cache with a
higher order if the index aligns with that order. Modify it so that the
order does not go below the mapping_min_order requirement of the page
cache. This function will do the right thing even if the new_order passed
is less than the mapping_min_order.
When adding new folios to the page cache we must also ensure the index
used is aligned to the mapping_min_order as the page cache requires the
index to be aligned to the order of the folio.

readahead_expand() is called from readahead aops to extend the range of
the readahead so this function can assume ractl->_index to be aligned with
min_order.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Co-developed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20240822135018.1931258-4-kernel@pankajraghav.com
Tested-by: David Howells <dhowells@redhat.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Pankaj Raghav 2024-08-22 15:50:11 +02:00 committed by Christian Brauner
parent c104d25f8c
commit 7949d4e70a
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 61 additions and 18 deletions
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79
mm/readahead.c
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@ -206,9 +206,10 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
unsigned long nr_to_read, unsigned long lookahead_size)
{
struct address_space *mapping = ractl->mapping;
unsigned long index = readahead_index(ractl);
unsigned long ra_folio_index, index = readahead_index(ractl);
gfp_t gfp_mask = readahead_gfp_mask(mapping);
unsigned long i;
unsigned long mark, i = 0;
unsigned int min_nrpages = mapping_min_folio_nrpages(mapping);
/*
* Partway through the readahead operation, we will have added
@ -223,10 +224,24 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
unsigned int nofs = memalloc_nofs_save();
filemap_invalidate_lock_shared(mapping);
index = mapping_align_index(mapping, index);
/*
* As iterator `i` is aligned to min_nrpages, round_up the
* difference between nr_to_read and lookahead_size to mark the
* index that only has lookahead or "async_region" to set the
* readahead flag.
*/
ra_folio_index = round_up(readahead_index(ractl) + nr_to_read - lookahead_size,
min_nrpages);
mark = ra_folio_index - index;
nr_to_read += readahead_index(ractl) - index;
ractl->_index = index;
/*
* Preallocate as many pages as we will need.
*/
for (i = 0; i < nr_to_read; i++) {
while (i < nr_to_read) {
struct folio *folio = xa_load(&mapping->i_pages, index + i);
int ret;
@ -240,12 +255,13 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
* not worth getting one just for that.
*/
read_pages(ractl);
ractl->_index++;
i = ractl->_index + ractl->_nr_pages - index - 1;
ractl->_index += min_nrpages;
i = ractl->_index + ractl->_nr_pages - index;
continue;
}
folio = filemap_alloc_folio(gfp_mask, 0);
folio = filemap_alloc_folio(gfp_mask,
mapping_min_folio_order(mapping));
if (!folio)
break;
@ -255,14 +271,15 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
if (ret == -ENOMEM)
break;
read_pages(ractl);
ractl->_index++;
i = ractl->_index + ractl->_nr_pages - index - 1;
ractl->_index += min_nrpages;
i = ractl->_index + ractl->_nr_pages - index;
continue;
}
if (i == nr_to_read - lookahead_size)
if (i == mark)
folio_set_readahead(folio);
ractl->_workingset |= folio_test_workingset(folio);
ractl->_nr_pages++;
ractl->_nr_pages += min_nrpages;
i += min_nrpages;
}
/*
@ -438,13 +455,19 @@ void page_cache_ra_order(struct readahead_control *ractl,
struct address_space *mapping = ractl->mapping;
pgoff_t start = readahead_index(ractl);
pgoff_t index = start;
unsigned int min_order = mapping_min_folio_order(mapping);
pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT;
pgoff_t mark = index + ra->size - ra->async_size;
unsigned int nofs;
int err = 0;
gfp_t gfp = readahead_gfp_mask(mapping);
unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping));
if (!mapping_large_folio_support(mapping) || ra->size < 4)
/*
* Fallback when size < min_nrpages as each folio should be
* at least min_nrpages anyway.
*/
if (!mapping_large_folio_support(mapping) || ra->size < min_ra_size)
goto fallback;
limit = min(limit, index + ra->size - 1);
@ -454,10 +477,19 @@ void page_cache_ra_order(struct readahead_control *ractl,
new_order = min(mapping_max_folio_order(mapping), new_order);
new_order = min_t(unsigned int, new_order, ilog2(ra->size));
new_order = max(new_order, min_order);
/* See comment in page_cache_ra_unbounded() */
nofs = memalloc_nofs_save();
filemap_invalidate_lock_shared(mapping);
/*
* If the new_order is greater than min_order and index is
* already aligned to new_order, then this will be noop as index
* aligned to new_order should also be aligned to min_order.
*/
ractl->_index = mapping_align_index(mapping, index);
index = readahead_index(ractl);
while (index <= limit) {
unsigned int order = new_order;
@ -465,7 +497,7 @@ void page_cache_ra_order(struct readahead_control *ractl,
if (index & ((1UL << order) - 1))
order = __ffs(index);
/* Don't allocate pages past EOF */
while (index + (1UL << order) - 1 > limit)
while (order > min_order && index + (1UL << order) - 1 > limit)
order--;
err = ra_alloc_folio(ractl, index, mark, order, gfp);
if (err)
@ -703,8 +735,15 @@ void readahead_expand(struct readahead_control *ractl,
struct file_ra_state *ra = ractl->ra;
pgoff_t new_index, new_nr_pages;
gfp_t gfp_mask = readahead_gfp_mask(mapping);
unsigned long min_nrpages = mapping_min_folio_nrpages(mapping);
unsigned int min_order = mapping_min_folio_order(mapping);
new_index = new_start / PAGE_SIZE;
/*
* Readahead code should have aligned the ractl->_index to
* min_nrpages before calling readahead aops.
*/
VM_BUG_ON(!IS_ALIGNED(ractl->_index, min_nrpages));
/* Expand the leading edge downwards */
while (ractl->_index > new_index) {
@ -714,9 +753,11 @@ void readahead_expand(struct readahead_control *ractl,
if (folio && !xa_is_value(folio))
return; /* Folio apparently present */
folio = filemap_alloc_folio(gfp_mask, 0);
folio = filemap_alloc_folio(gfp_mask, min_order);
if (!folio)
return;
index = mapping_align_index(mapping, index);
if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) {
folio_put(folio);
return;
@ -726,7 +767,7 @@ void readahead_expand(struct readahead_control *ractl,
ractl->_workingset = true;
psi_memstall_enter(&ractl->_pflags);
}
ractl->_nr_pages++;
ractl->_nr_pages += min_nrpages;
ractl->_index = folio->index;
}
@ -741,9 +782,11 @@ void readahead_expand(struct readahead_control *ractl,
if (folio && !xa_is_value(folio))
return; /* Folio apparently present */
folio = filemap_alloc_folio(gfp_mask, 0);
folio = filemap_alloc_folio(gfp_mask, min_order);
if (!folio)
return;
index = mapping_align_index(mapping, index);
if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) {
folio_put(folio);
return;
@ -753,10 +796,10 @@ void readahead_expand(struct readahead_control *ractl,
ractl->_workingset = true;
psi_memstall_enter(&ractl->_pflags);
}
ractl->_nr_pages++;
ractl->_nr_pages += min_nrpages;
if (ra) {
ra->size++;
ra->async_size++;
ra->size += min_nrpages;
ra->async_size += min_nrpages;
}
}
}