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mm/filemap: Allow large folios to be added to the page cache 

We return -EEXIST if there are any non-shadow entries in the page
cache in the range covered by the folio.  If there are multiple
shadow entries in the range, we set *shadowp to one of them (currently
the one at the highest index).  If that turns out to be the wrong
answer, we can implement something more complex.  This is mostly
modelled after the equivalent function in the shmem code.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2019-09-05 14:03:12 -04:00
parent d4b4084ac3
commit d68eccad37
1 changed files with 22 additions and 17 deletions
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39
mm/filemap.c
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@ -842,26 +842,27 @@ noinline int __filemap_add_folio(struct address_space *mapping,
{ {
XA_STATE(xas, &mapping->i_pages, index); XA_STATE(xas, &mapping->i_pages, index);
int huge = folio_test_hugetlb(folio); int huge = folio_test_hugetlb(folio);
int error;
bool charged = false; bool charged = false;
long nr = 1;
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio); VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
mapping_set_update(&xas, mapping); mapping_set_update(&xas, mapping);
folio_get(folio);
folio->mapping = mapping;
folio->index = index;
if (!huge) { if (!huge) {
error = mem_cgroup_charge(folio, NULL, gfp); int error = mem_cgroup_charge(folio, NULL, gfp);
VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio); VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
if (error) if (error)
goto error; return error;
charged = true; charged = true;
xas_set_order(&xas, index, folio_order(folio));
nr = folio_nr_pages(folio);
} }
gfp &= GFP_RECLAIM_MASK; gfp &= GFP_RECLAIM_MASK;
folio_ref_add(folio, nr);
folio->mapping = mapping;
folio->index = xas.xa_index;
do { do {
unsigned int order = xa_get_order(xas.xa, xas.xa_index); unsigned int order = xa_get_order(xas.xa, xas.xa_index);
@ -885,6 +886,8 @@ noinline int __filemap_add_folio(struct address_space *mapping,
/* entry may have been split before we acquired lock */ /* entry may have been split before we acquired lock */
order = xa_get_order(xas.xa, xas.xa_index); order = xa_get_order(xas.xa, xas.xa_index);
if (order > folio_order(folio)) { if (order > folio_order(folio)) {
/* How to handle large swap entries? */
BUG_ON(shmem_mapping(mapping));
xas_split(&xas, old, order); xas_split(&xas, old, order);
xas_reset(&xas); xas_reset(&xas);
} }
@ -894,29 +897,31 @@ noinline int __filemap_add_folio(struct address_space *mapping,
if (xas_error(&xas)) if (xas_error(&xas))
goto unlock; goto unlock;
mapping->nrpages++; mapping->nrpages += nr;
/* hugetlb pages do not participate in page cache accounting */ /* hugetlb pages do not participate in page cache accounting */
if (!huge) if (!huge) {
__lruvec_stat_add_folio(folio, NR_FILE_PAGES); __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
if (folio_test_pmd_mappable(folio))
__lruvec_stat_mod_folio(folio,
NR_FILE_THPS, nr);
}
unlock: unlock:
xas_unlock_irq(&xas); xas_unlock_irq(&xas);
} while (xas_nomem(&xas, gfp)); } while (xas_nomem(&xas, gfp));
if (xas_error(&xas)) { if (xas_error(&xas))
error = xas_error(&xas);
if (charged)
mem_cgroup_uncharge(folio);
goto error; goto error;
}
trace_mm_filemap_add_to_page_cache(folio); trace_mm_filemap_add_to_page_cache(folio);
return 0; return 0;
error: error:
if (charged)
mem_cgroup_uncharge(folio);
folio->mapping = NULL; folio->mapping = NULL;
/* Leave page->index set: truncation relies upon it */ /* Leave page->index set: truncation relies upon it */
folio_put(folio); folio_put_refs(folio, nr);
return error; return xas_error(&xas);
} }
ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO); ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);