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Removing ZERO_PAGE abd_alloc_zero_scatter #10428

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merged 1 commit into from
Jun 11, 2020
Merged

Removing ZERO_PAGE abd_alloc_zero_scatter #10428

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1 change: 0 additions & 1 deletion include/sys/abd.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@ typedef int abd_iter_func_t(void *buf, size_t len, void *priv);
typedef int abd_iter_func2_t(void *bufa, void *bufb, size_t len, void *priv);

extern int zfs_abd_scatter_enabled;
extern abd_t *abd_zero_scatter;

/*
* Allocations and deallocations
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2 changes: 2 additions & 0 deletions include/sys/abd_impl.h
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Expand Up @@ -92,6 +92,8 @@ struct abd_iter {
struct scatterlist *iter_sg; /* current sg */
};

extern abd_t *abd_zero_scatter;

abd_t *abd_gang_get_offset(abd_t *, size_t *);

/*
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33 changes: 21 additions & 12 deletions module/os/linux/zfs/abd_os.c
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Expand Up @@ -167,6 +167,13 @@ int zfs_abd_scatter_min_size = 512 * 3;
*/
abd_t *abd_zero_scatter = NULL;

struct page;
/*
* abd_zero_page we will be an allocated zero'd PAGESIZE buffer, which is
* assigned to set each of the pages of abd_zero_scatter.
*/
static struct page *abd_zero_page = NULL;

static kmem_cache_t *abd_cache = NULL;
static kstat_t *abd_ksp;

Expand Down Expand Up @@ -439,18 +446,24 @@ abd_free_chunks(abd_t *abd)

/*
* Allocate scatter ABD of size SPA_MAXBLOCKSIZE, where each page in
* the scatterlist will be set to ZERO_PAGE(0). ZERO_PAGE(0) returns
* a global shared page that is always zero'd out.
* the scatterlist will be set to the zero'd out buffer abd_zero_page.
*/
static void
abd_alloc_zero_scatter(void)
{
struct scatterlist *sg = NULL;
struct sg_table table;
gfp_t gfp = __GFP_NOWARN | GFP_NOIO;
gfp_t gfp_zero_page = gfp | __GFP_ZERO;
int nr_pages = abd_chunkcnt_for_bytes(SPA_MAXBLOCKSIZE);
int i = 0;

while ((abd_zero_page = __page_cache_alloc(gfp_zero_page)) == NULL) {
ABDSTAT_BUMP(abdstat_scatter_page_alloc_retry);
schedule_timeout_interruptible(1);
}
abd_mark_zfs_page(abd_zero_page);

while (sg_alloc_table(&table, nr_pages, gfp)) {
ABDSTAT_BUMP(abdstat_scatter_sg_table_retry);
schedule_timeout_interruptible(1);
Expand All @@ -468,7 +481,7 @@ abd_alloc_zero_scatter(void)
zfs_refcount_create(&abd_zero_scatter->abd_children);

abd_for_each_sg(abd_zero_scatter, sg, nr_pages, i) {
sg_set_page(sg, ZERO_PAGE(0), PAGESIZE, 0);
sg_set_page(sg, abd_zero_page, PAGESIZE, 0);
}

ABDSTAT_BUMP(abdstat_scatter_cnt);
Expand All @@ -478,14 +491,6 @@ abd_alloc_zero_scatter(void)

#else /* _KERNEL */

struct page;

/*
* In user space abd_zero_page we will be an allocated zero'd PAGESIZE
* buffer, which is assigned to set each of the pages of abd_zero_scatter.
*/
static struct page *abd_zero_page = NULL;

#ifndef PAGE_SHIFT
#define PAGE_SHIFT (highbit64(PAGESIZE)-1)
#endif
Expand Down Expand Up @@ -680,7 +685,11 @@ abd_free_zero_scatter(void)
abd_free_sg_table(abd_zero_scatter);
abd_free_struct(abd_zero_scatter);
abd_zero_scatter = NULL;
#if !defined(_KERNEL)
ASSERT3P(abd_zero_page, !=, NULL);
#if defined(_KERNEL)
abd_unmark_zfs_page(abd_zero_page);
__free_page(abd_zero_page);
#else
umem_free(abd_zero_page, PAGESIZE);
#endif /* _KERNEL */
}
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