[PATCH 2/4] erofs: get rid of `z_erofs_next_pcluster_t`

Gao Xiang
2025-01-14T03:44:46Z

It was originally intended for tagged pointer reservation.

Now all encoded data can be represented uniformally with
`struct z_erofs_pcluster` as described in commit bf1aa03980f4
("erofs: sunset `struct erofs_workgroup`"), let's drop it too.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
fs/erofs/zdata.c | 80 ++++++++++++++++++------------------------------
1 file changed, 29 insertions(+), 51 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 19ef4ff2a134..8bafc4d9edbe 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -12,12 +12,6 @@
#define Z_EROFS_PCLUSTER_MAX_PAGES (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
#define Z_EROFS_INLINE_BVECS 2

-/*
- * let's leave a type here in case of introducing
- * another tagged pointer later.
- */
-typedef void *z_erofs_next_pcluster_t;
-
struct z_erofs_bvec {
struct page *page;
int offset;
@@ -48,7 +42,7 @@ struct z_erofs_pcluster {
struct lockref lockref;

/* A: point to next chained pcluster or TAILs */
- z_erofs_next_pcluster_t next;
+ struct z_erofs_pcluster *next;

/* I: start block address of this pcluster */
erofs_off_t index;
@@ -94,12 +88,11 @@ struct z_erofs_pcluster {

/* the end of a chain of pclusters */
#define Z_EROFS_PCLUSTER_TAIL ((void *) 0x700 + POISON_POINTER_DELTA)
-#define Z_EROFS_PCLUSTER_NIL (NULL)

struct z_erofs_decompressqueue {
struct super_block *sb;
+ struct z_erofs_pcluster *head;
atomic_t pending_bios;
- z_erofs_next_pcluster_t head;

union {
struct completion done;
@@ -493,8 +486,7 @@ struct z_erofs_decompress_frontend {

struct page *pagepool;
struct page *candidate_bvpage;
- struct z_erofs_pcluster *pcl;
- z_erofs_next_pcluster_t owned_head;
+ struct z_erofs_pcluster *pcl, *head;
enum z_erofs_pclustermode mode;

erofs_off_t headoffset;
@@ -504,7 +496,7 @@ struct z_erofs_decompress_frontend {
};

#define DECOMPRESS_FRONTEND_INIT(__i) { \
- .inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
+ .inode = __i, .head = Z_EROFS_PCLUSTER_TAIL, \
.mode = Z_EROFS_PCLUSTER_FOLLOWED }

static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
@@ -752,9 +744,7 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
pcl->algorithmformat = map->m_algorithmformat;
pcl->length = 0;
pcl->partial = true;
-
- /* new pclusters should be claimed as type 1, primary and followed */
- pcl->next = fe->owned_head;
+ pcl->next = fe->head;
pcl->pageofs_out = map->m_la & ~PAGE_MASK;
fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;

@@ -790,8 +780,7 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
goto err_out;
}
}
- fe->owned_head = &pcl->next;
- fe->pcl = pcl;
+ fe->head = fe->pcl = pcl;
return 0;

err_out:
@@ -810,7 +799,7 @@ static int z_erofs_pcluster_begin(struct z_erofs_decompress_frontend *fe)

DBG_BUGON(fe->pcl);
/* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous pcluster */
- DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
+ DBG_BUGON(!fe->head);

if (!(map->m_flags & EROFS_MAP_META)) {
while (1) {
@@ -838,10 +827,9 @@ static int z_erofs_pcluster_begin(struct z_erofs_decompress_frontend *fe)
if (ret == -EEXIST) {
mutex_lock(&fe->pcl->lock);
/* check if this pcluster hasn't been linked into any chain. */
- if (cmpxchg(&fe->pcl->next, Z_EROFS_PCLUSTER_NIL,
- fe->owned_head) == Z_EROFS_PCLUSTER_NIL) {
+ if (!cmpxchg(&fe->pcl->next, NULL, fe->head)) {
/* .. so it can be attached to our submission chain */
- fe->owned_head = &fe->pcl->next;
+ fe->head = fe->pcl;
fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;
} else { /* otherwise, it belongs to an inflight chain */
fe->mode = Z_EROFS_PCLUSTER_INFLIGHT;
@@ -1394,7 +1382,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
pcl->vcnt = 0;

/* pcluster lock MUST be taken before the following line */
- WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
+ WRITE_ONCE(pcl->next, NULL);
mutex_unlock(&pcl->lock);

if (z_erofs_is_inline_pcluster(pcl))
@@ -1412,16 +1400,14 @@ static int z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
.pagepool = pagepool,
.decompressed_secondary_bvecs =
LIST_HEAD_INIT(be.decompressed_secondary_bvecs),
+ .pcl = io->head,
};
- z_erofs_next_pcluster_t owned = io->head;
+ struct z_erofs_pcluster *next;
int err = io->eio ? -EIO : 0;

- while (owned != Z_EROFS_PCLUSTER_TAIL) {
- DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
-
- be.pcl = container_of(owned, struct z_erofs_pcluster, next);
- owned = READ_ONCE(be.pcl->next);
-
+ for (; be.pcl != Z_EROFS_PCLUSTER_TAIL; be.pcl = next) {
+ DBG_BUGON(!be.pcl);
+ next = READ_ONCE(be.pcl->next);
err = z_erofs_decompress_pcluster(&be, err) ?: err;
}
return err;
@@ -1631,18 +1617,13 @@ enum {
NR_JOBQUEUES,
};

-static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
- z_erofs_next_pcluster_t qtail[],
- z_erofs_next_pcluster_t owned_head)
+static void z_erofs_move_to_bypass_queue(struct z_erofs_pcluster *pcl,
+ struct z_erofs_pcluster *next,
+ struct z_erofs_pcluster **qtail[])
{
- z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
- z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
-
WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL);
-
- WRITE_ONCE(*submit_qtail, owned_head);
- WRITE_ONCE(*bypass_qtail, &pcl->next);
-
+ WRITE_ONCE(*qtail[JQ_SUBMIT], next);
+ WRITE_ONCE(*qtail[JQ_BYPASS], pcl);
qtail[JQ_BYPASS] = &pcl->next;
}

@@ -1677,9 +1658,9 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
{
struct super_block *sb = f->inode->i_sb;
struct address_space *mc = MNGD_MAPPING(EROFS_SB(sb));
- z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
+ struct z_erofs_pcluster **qtail[NR_JOBQUEUES];
struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
- z_erofs_next_pcluster_t owned_head = f->owned_head;
+ struct z_erofs_pcluster *pcl, *next;
/* bio is NULL initially, so no need to initialize last_{index,bdev} */
erofs_off_t last_pa;
unsigned int nr_bios = 0;
@@ -1695,22 +1676,19 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
qtail[JQ_SUBMIT] = &q[JQ_SUBMIT]->head;

/* by default, all need io submission */
- q[JQ_SUBMIT]->head = owned_head;
+ q[JQ_SUBMIT]->head = next = f->head;

do {
struct erofs_map_dev mdev;
- struct z_erofs_pcluster *pcl;
erofs_off_t cur, end;
struct bio_vec bvec;
unsigned int i = 0;
bool bypass = true;

- DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
- pcl = container_of(owned_head, struct z_erofs_pcluster, next);
- owned_head = READ_ONCE(pcl->next);
-
+ pcl = next;
+ next = READ_ONCE(pcl->next);
if (z_erofs_is_inline_pcluster(pcl)) {
- move_to_bypass_jobqueue(pcl, qtail, owned_head);
+ z_erofs_move_to_bypass_queue(pcl, next, qtail);
continue;
}

@@ -1782,8 +1760,8 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
if (!bypass)
qtail[JQ_SUBMIT] = &pcl->next;
else
- move_to_bypass_jobqueue(pcl, qtail, owned_head);
- } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
+ z_erofs_move_to_bypass_queue(pcl, next, qtail);
+ } while (next != Z_EROFS_PCLUSTER_TAIL);

if (bio) {
if (erofs_is_fileio_mode(EROFS_SB(sb)))
@@ -1815,7 +1793,7 @@ static int z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
bool force_fg = z_erofs_is_sync_decompress(sbi, ra_folios);
int err;

- if (f->owned_head == Z_EROFS_PCLUSTER_TAIL)
+ if (f->head == Z_EROFS_PCLUSTER_TAIL)
return 0;
z_erofs_submit_queue(f, io, &force_fg, !!ra_folios);

--
2.43.5