Hi Gao, Hi Jan,

On 7/9/25 5:46 AM, Gao Xiang wrote:
Flush the D-cache before unlocking folios for compressed inodes, as
they are dirtied during decompression.

Avoid calling flush_dcache_folio() on every CPU write, since it's more
like playing whack-a-mole without real benefit.

It has no impact on x86 and arm64/risc-v: on x86, flush_dcache_folio()
is a no-op, and on arm64/risc-v, PG_dcache_clean (PG_arch_1) is clear
for new page cache folios.  However, certain ARM boards are affected,
as reported.

Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Closes: 
https://lore.kernel.org/r/c1e51e16-6cc6-49d0-a63e-4e9ff6c4d...@pengutronix.de
Closes: 
https://lore.kernel.org/r/38d43fae-1182-4155-9c5b-ffc7382d9...@siemens.com
Cc: Jan Kiszka <jan.kis...@siemens.com>
Cc: Stefan Kerkmann <s.kerkm...@pengutronix.de>
Signed-off-by: Gao Xiang <hsiang...@linux.alibaba.com>
---
Hi Jan and Stefan,

if possible, please help test this patch on your arm devices,
many thanks!  I will submit this later but if it's urgent you
could also apply this locally in advance.


Thank you for the fix and great work, it solved the issue I was seeing locally!

Thanks,
Gao Xiang
  fs/erofs/data.c         | 16 +++++++++++-----
  fs/erofs/decompressor.c | 12 ++++--------
  fs/erofs/fileio.c       |  4 ++--
  fs/erofs/internal.h     |  2 +-
  fs/erofs/zdata.c        |  6 +++---
  5 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 221e0ff1ed0d..16e4a6bd9b97 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -214,9 +214,11 @@ int erofs_map_dev(struct super_block *sb, struct 
erofs_map_dev *map)
/*
   * bit 30: I/O error occurred on this folio
+ * bit 29: CPU has dirty data in D-cache (needs aliasing handling);
   * bit 0 - 29: remaining parts to complete this folio
   */
-#define EROFS_ONLINEFOLIO_EIO                  (1 << 30)
+#define EROFS_ONLINEFOLIO_EIO          30
+#define EROFS_ONLINEFOLIO_DIRTY                29
void erofs_onlinefolio_init(struct folio *folio)
  {
@@ -233,19 +235,23 @@ void erofs_onlinefolio_split(struct folio *folio)
        atomic_inc((atomic_t *)&folio->private);
  }
-void erofs_onlinefolio_end(struct folio *folio, int err)
+void erofs_onlinefolio_end(struct folio *folio, int err, bool dirty)
  {
        int orig, v;
do {
                orig = atomic_read((atomic_t *)&folio->private);
-               v = (orig - 1) | (err ? EROFS_ONLINEFOLIO_EIO : 0);
+               DBG_BUGON(orig <= 0);
+               v = dirty << EROFS_ONLINEFOLIO_DIRTY;
+               v |= (orig - 1) | (!!err << EROFS_ONLINEFOLIO_EIO);
        } while (atomic_cmpxchg((atomic_t *)&folio->private, orig, v) != orig);
- if (v & ~EROFS_ONLINEFOLIO_EIO)
+       if (v & (BIT(EROFS_ONLINEFOLIO_DIRTY) - 1))
                return;
        folio->private = 0;
-       folio_end_read(folio, !(v & EROFS_ONLINEFOLIO_EIO));
+       if (v & BIT(EROFS_ONLINEFOLIO_DIRTY))
+               flush_dcache_folio(folio);
+       folio_end_read(folio, !(v & BIT(EROFS_ONLINEFOLIO_EIO)));
  }
static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index bf62e2836b60..358061d7b660 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -301,13 +301,11 @@ static int z_erofs_transform_plain(struct 
z_erofs_decompress_req *rq,
                cur = min(cur, rq->outputsize);
                if (cur && rq->out[0]) {
                        kin = kmap_local_page(rq->in[nrpages_in - 1]);
-                       if (rq->out[0] == rq->in[nrpages_in - 1]) {
+                       if (rq->out[0] == rq->in[nrpages_in - 1])
                                memmove(kin + rq->pageofs_out, kin + pi, cur);
-                               flush_dcache_page(rq->out[0]);
-                       } else {
+                       else
                                memcpy_to_page(rq->out[0], rq->pageofs_out,
                                               kin + pi, cur);
-                       }
                        kunmap_local(kin);
                }
                rq->outputsize -= cur;
@@ -325,14 +323,12 @@ static int z_erofs_transform_plain(struct 
z_erofs_decompress_req *rq,
                        po = (rq->pageofs_out + cur + pi) & ~PAGE_MASK;
                        DBG_BUGON(no >= nrpages_out);
                        cnt = min(insz - pi, PAGE_SIZE - po);
-                       if (rq->out[no] == rq->in[ni]) {
+                       if (rq->out[no] == rq->in[ni])
                                memmove(kin + po,
                                        kin + rq->pageofs_in + pi, cnt);
-                               flush_dcache_page(rq->out[no]);
-                       } else if (rq->out[no]) {
+                       else if (rq->out[no])
                                memcpy_to_page(rq->out[no], po,
                                               kin + rq->pageofs_in + pi, cnt);
-                       }
                        pi += cnt;
                } while (pi < insz);
                kunmap_local(kin);
diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c
index fe2cd2982b4b..91781718199e 100644
--- a/fs/erofs/fileio.c
+++ b/fs/erofs/fileio.c
@@ -38,7 +38,7 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long 
ret)
        } else {
                bio_for_each_folio_all(fi, &rq->bio) {
                        DBG_BUGON(folio_test_uptodate(fi.folio));
-                       erofs_onlinefolio_end(fi.folio, ret);
+                       erofs_onlinefolio_end(fi.folio, ret, false);
                }
        }
        bio_uninit(&rq->bio);
@@ -154,7 +154,7 @@ static int erofs_fileio_scan_folio(struct erofs_fileio *io, 
struct folio *folio)
                }
                cur += len;
        }
-       erofs_onlinefolio_end(folio, err);
+       erofs_onlinefolio_end(folio, err, false);
        return err;
  }
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index a32c03a80c70..0d19bde8c094 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -390,7 +390,7 @@ int erofs_fiemap(struct inode *inode, struct 
fiemap_extent_info *fieinfo,
  int erofs_map_blocks(struct inode *inode, struct erofs_map_blocks *map);
  void erofs_onlinefolio_init(struct folio *folio);
  void erofs_onlinefolio_split(struct folio *folio);
-void erofs_onlinefolio_end(struct folio *folio, int err);
+void erofs_onlinefolio_end(struct folio *folio, int err, bool dirty);
  struct inode *erofs_iget(struct super_block *sb, erofs_nid_t nid);
  int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
                  struct kstat *stat, u32 request_mask,
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index d80e3bf4fa79..6f8402ed5b28 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1090,7 +1090,7 @@ static int z_erofs_scan_folio(struct z_erofs_frontend *f,
                        tight = (bs == PAGE_SIZE);
                }
        } while ((end = cur) > 0);
-       erofs_onlinefolio_end(folio, err);
+       erofs_onlinefolio_end(folio, err, false);
        return err;
  }
@@ -1195,7 +1195,7 @@ static void z_erofs_fill_other_copies(struct z_erofs_backend *be, int err)
                        cur += len;
                }
                kunmap_local(dst);
-               erofs_onlinefolio_end(page_folio(bvi->bvec.page), err);
+               erofs_onlinefolio_end(page_folio(bvi->bvec.page), err, true);
                list_del(p);
                kfree(bvi);
        }
@@ -1353,7 +1353,7 @@ static int z_erofs_decompress_pcluster(struct 
z_erofs_backend *be, int err)
DBG_BUGON(z_erofs_page_is_invalidated(page));
                if (!z_erofs_is_shortlived_page(page)) {
-                       erofs_onlinefolio_end(page_folio(page), err);
+                       erofs_onlinefolio_end(page_folio(page), err, true);
                        continue;
                }
                if (pcl->algorithmformat != Z_EROFS_COMPRESSION_LZ4) {

Tested-by: Stefan Kerkmann <s.kerkm...@pengutronix.de>

Best regards,
Stefan

--
Pengutronix e.K.                       | Stefan Kerkmann             |
Steuerwalder Str. 21                   | https://www.pengutronix.de/ |
31137 Hildesheim, Germany              | Phone: +49-5121-206917-128  |
Amtsgericht Hildesheim, HRA 2686       | Fax:   +49-5121-206917-9    |


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