[PATCH v2 08/16] erofs: rework online page handling

From: Gao Xiang
Date: Fri Jul 15 2022 - 11:42:57 EST

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Since all decompressed offsets have been integrated to bvecs[], this
patch avoids all sub-indexes so that page->private only includes a
part count and an eio flag, thus in the future folio->private can have
the same meaning.

In addition, PG_error will not be used anymore after this patch and
we're heading to use page->private (later folio->private) and
page->mapping (later folio->mapping) only.

Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
---
fs/erofs/zdata.c | 57 ++++++++++++++++------------------------
fs/erofs/zdata.h | 68 ++++++++++++++----------------------------------
2 files changed, 42 insertions(+), 83 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 2ea8c97be5b6..2d5e2ed3e5f5 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -743,7 +743,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
map->m_llen = 0;
err = z_erofs_map_blocks_iter(inode, map, 0);
if (err)
- goto err_out;
+ goto out;
} else {
if (fe->pcl)
goto hitted;
@@ -755,7 +755,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,

err = z_erofs_collector_begin(fe);
if (err)
- goto err_out;
+ goto out;

if (z_erofs_is_inline_pcluster(fe->pcl)) {
void *mp;
@@ -766,7 +766,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
err = PTR_ERR(mp);
erofs_err(inode->i_sb,
"failed to get inline page, err %d", err);
- goto err_out;
+ goto out;
}
get_page(fe->map.buf.page);
WRITE_ONCE(fe->pcl->compressed_bvecs[0].page,
@@ -823,16 +823,15 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,

if (err) {
DBG_BUGON(err == -EAGAIN && fe->candidate_bvpage);
- goto err_out;
+ goto out;
}

- index = page->index - (map->m_la >> PAGE_SHIFT);
-
- z_erofs_onlinepage_fixup(page, index, true);
-
+ z_erofs_onlinepage_split(page);
/* bump up the number of spiltted parts of a page */
++spiltted;
+
/* also update nr_pages */
+ index = page->index - (map->m_la >> PAGE_SHIFT);
fe->pcl->nr_pages = max_t(pgoff_t, fe->pcl->nr_pages, index + 1);
next_part:
/* can be used for verification */
@@ -843,16 +842,13 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
goto repeat;

out:
+ if (err)
+ z_erofs_page_mark_eio(page);
z_erofs_onlinepage_endio(page);

erofs_dbg("%s, finish page: %pK spiltted: %u map->m_llen %llu",
__func__, page, spiltted, map->m_llen);
return err;
-
- /* if some error occurred while processing this page */
-err_out:
- SetPageError(page);
- goto out;
}

static bool z_erofs_get_sync_decompress_policy(struct erofs_sb_info *sbi,
@@ -901,7 +897,7 @@ static int z_erofs_parse_out_bvecs(struct z_erofs_pcluster *pcl,
*/
if (pages[pagenr]) {
DBG_BUGON(1);
- SetPageError(pages[pagenr]);
+ z_erofs_page_mark_eio(pages[pagenr]);
z_erofs_onlinepage_endio(pages[pagenr]);
err = -EFSCORRUPTED;
}
@@ -957,19 +953,13 @@ static struct page **z_erofs_parse_in_bvecs(struct erofs_sb_info *sbi,
DBG_BUGON(pgnr >= pcl->nr_pages);
if (pages[pgnr]) {
DBG_BUGON(1);
- SetPageError(pages[pgnr]);
+ z_erofs_page_mark_eio(pages[pgnr]);
z_erofs_onlinepage_endio(pages[pgnr]);
err = -EFSCORRUPTED;
}
pages[pgnr] = page;
*overlapped = true;
}
-
- /* PG_error needs checking for all non-managed pages */
- if (PageError(page)) {
- DBG_BUGON(PageUptodate(page));
- err = -EIO;
- }
}

if (err) {
@@ -981,16 +971,15 @@ static struct page **z_erofs_parse_in_bvecs(struct erofs_sb_info *sbi,

static int z_erofs_decompress_pcluster(struct super_block *sb,
struct z_erofs_pcluster *pcl,
- struct page **pagepool)
+ struct page **pagepool, int err)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
unsigned int i, inputsize, outputsize, llen, nr_pages;
struct page *pages_onstack[Z_EROFS_VMAP_ONSTACK_PAGES];
struct page **pages, **compressed_pages, *page;
-
+ int err2;
bool overlapped, partial;
- int err;

might_sleep();
DBG_BUGON(!READ_ONCE(pcl->nr_pages));
@@ -1022,7 +1011,9 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
for (i = 0; i < nr_pages; ++i)
pages[i] = NULL;

- err = z_erofs_parse_out_bvecs(pcl, pages, pagepool);
+ err2 = z_erofs_parse_out_bvecs(pcl, pages, pagepool);
+ if (err2)
+ err = err2;
compressed_pages = z_erofs_parse_in_bvecs(sbi, pcl, pages,
pagepool, &overlapped);
if (IS_ERR(compressed_pages)) {
@@ -1090,10 +1081,8 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
/* recycle all individual short-lived pages */
if (z_erofs_put_shortlivedpage(pagepool, page))
continue;
-
- if (err < 0)
- SetPageError(page);
-
+ if (err)
+ z_erofs_page_mark_eio(page);
z_erofs_onlinepage_endio(page);
}

@@ -1129,7 +1118,8 @@ static void z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
pcl = container_of(owned, struct z_erofs_pcluster, next);
owned = READ_ONCE(pcl->next);

- z_erofs_decompress_pcluster(io->sb, pcl, pagepool);
+ z_erofs_decompress_pcluster(io->sb, pcl, pagepool,
+ io->eio ? -EIO : 0);
erofs_workgroup_put(&pcl->obj);
}
}
@@ -1233,7 +1223,6 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
if (page->mapping == mc) {
WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);

- ClearPageError(page);
if (!PagePrivate(page)) {
/*
* impossible to be !PagePrivate(page) for
@@ -1305,6 +1294,7 @@ jobqueue_init(struct super_block *sb,
q = fgq;
init_completion(&fgq->u.done);
atomic_set(&fgq->pending_bios, 0);
+ q->eio = false;
}
q->sb = sb;
q->head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
@@ -1365,15 +1355,14 @@ static void z_erofs_decompressqueue_endio(struct bio *bio)
DBG_BUGON(PageUptodate(page));
DBG_BUGON(z_erofs_page_is_invalidated(page));

- if (err)
- SetPageError(page);
-
if (erofs_page_is_managed(EROFS_SB(q->sb), page)) {
if (!err)
SetPageUptodate(page);
unlock_page(page);
}
}
+ if (err)
+ q->eio = true;
z_erofs_decompress_kickoff(q, tagptr_unfold_tags(t), -1);
bio_put(bio);
}
diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
index 5d236c8b40c5..75f6fd435388 100644
--- a/fs/erofs/zdata.h
+++ b/fs/erofs/zdata.h
@@ -109,6 +109,8 @@ struct z_erofs_decompressqueue {
struct completion done;
struct work_struct work;
} u;
+
+ bool eio;
};

static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
@@ -123,38 +125,17 @@ static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
return pcl->pclusterpages;
}

-#define Z_EROFS_ONLINEPAGE_COUNT_BITS 2
-#define Z_EROFS_ONLINEPAGE_COUNT_MASK ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) - 1)
-#define Z_EROFS_ONLINEPAGE_INDEX_SHIFT (Z_EROFS_ONLINEPAGE_COUNT_BITS)
-
/*
- * waiters (aka. ongoing_packs): # to unlock the page
- * sub-index: 0 - for partial page, >= 1 full page sub-index
+ * bit 31: I/O error occurred on this page
+ * bit 0 - 30: remaining parts to complete this page
*/
-typedef atomic_t z_erofs_onlinepage_t;
-
-/* type punning */
-union z_erofs_onlinepage_converter {
- z_erofs_onlinepage_t *o;
- unsigned long *v;
-};
-
-static inline unsigned int z_erofs_onlinepage_index(struct page *page)
-{
- union z_erofs_onlinepage_converter u;
-
- DBG_BUGON(!PagePrivate(page));
- u.v = &page_private(page);
-
- return atomic_read(u.o) >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
-}
+#define Z_EROFS_PAGE_EIO (1 << 31)

static inline void z_erofs_onlinepage_init(struct page *page)
{
union {
- z_erofs_onlinepage_t o;
+ atomic_t o;
unsigned long v;
- /* keep from being unlocked in advance */
} u = { .o = ATOMIC_INIT(1) };

set_page_private(page, u.v);
@@ -162,45 +143,34 @@ static inline void z_erofs_onlinepage_init(struct page *page)
SetPagePrivate(page);
}

-static inline void z_erofs_onlinepage_fixup(struct page *page,
- uintptr_t index, bool down)
+static inline void z_erofs_onlinepage_split(struct page *page)
{
- union z_erofs_onlinepage_converter u = { .v = &page_private(page) };
- int orig, orig_index, val;
-
-repeat:
- orig = atomic_read(u.o);
- orig_index = orig >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
- if (orig_index) {
- if (!index)
- return;
+ atomic_inc((atomic_t *)&page->private);
+}

- DBG_BUGON(orig_index != index);
- }
+static inline void z_erofs_page_mark_eio(struct page *page)
+{
+ int orig;

- val = (index << Z_EROFS_ONLINEPAGE_INDEX_SHIFT) |
- ((orig & Z_EROFS_ONLINEPAGE_COUNT_MASK) + (unsigned int)down);
- if (atomic_cmpxchg(u.o, orig, val) != orig)
- goto repeat;
+ do {
+ orig = atomic_read((atomic_t *)&page->private);
+ } while (atomic_cmpxchg((atomic_t *)&page->private, orig,
+ orig | Z_EROFS_PAGE_EIO) != orig);
}

static inline void z_erofs_onlinepage_endio(struct page *page)
{
- union z_erofs_onlinepage_converter u;
unsigned int v;

DBG_BUGON(!PagePrivate(page));
- u.v = &page_private(page);
-
- v = atomic_dec_return(u.o);
- if (!(v & Z_EROFS_ONLINEPAGE_COUNT_MASK)) {
+ v = atomic_dec_return((atomic_t *)&page->private);
+ if (!(v & ~Z_EROFS_PAGE_EIO)) {
set_page_private(page, 0);
ClearPagePrivate(page);
- if (!PageError(page))
+ if (!(v & Z_EROFS_PAGE_EIO))
SetPageUptodate(page);
unlock_page(page);
}
- erofs_dbg("%s, page %p value %x", __func__, page, atomic_read(u.o));
}

#define Z_EROFS_VMAP_ONSTACK_PAGES \
--
2.24.4

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