Re: [PATCH RFC] fs: erofs: support PG_mappedtodisk flag for folios with zero-filled

From: Gao Xiang
Date: Thu Oct 17 2024 - 03:59:23 EST


Hi Barry,

On 2024/10/17 15:43, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>

When a folio has never been zero-filled, mark it as mappedtodisk
to allow other software components to recognize and utilize the
flag.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>

Thanks for this!

It looks good to me as an improvement as long as PG_mappedtodisk
is long-term lived and useful to users.

Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

Thanks,
Gao Xiang

---
fs/erofs/fileio.c | 2 ++
fs/erofs/zdata.c | 6 +++++-
2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c
index 3af96b1e2c2a..aa4cb438ea95 100644
--- a/fs/erofs/fileio.c
+++ b/fs/erofs/fileio.c
@@ -88,6 +88,7 @@ static int erofs_fileio_scan_folio(struct erofs_fileio *io, struct folio *folio)
struct erofs_map_blocks *map = &io->map;
unsigned int cur = 0, end = folio_size(folio), len, attached = 0;
loff_t pos = folio_pos(folio), ofs;
+ bool fully_mapped = true;
struct iov_iter iter;
struct bio_vec bv;
int err = 0;
@@ -124,6 +125,7 @@ static int erofs_fileio_scan_folio(struct erofs_fileio *io, struct folio *folio)
erofs_put_metabuf(&buf);
} else if (!(map->m_flags & EROFS_MAP_MAPPED)) {
folio_zero_segment(folio, cur, cur + len);
+ fully_mapped = false;
attached = 0;
} else {
if (io->rq && (map->m_pa + ofs != io->dev.m_pa ||
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 8936790618c6..0158de4f3d95 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -926,7 +926,7 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
const loff_t offset = folio_pos(folio);
const unsigned int bs = i_blocksize(inode);
unsigned int end = folio_size(folio), split = 0, cur, pgs;
- bool tight, excl;
+ bool tight, excl, fully_mapped = true;
int err = 0;
tight = (bs == PAGE_SIZE);
@@ -949,6 +949,7 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
if (!(map->m_flags & EROFS_MAP_MAPPED)) {
folio_zero_segment(folio, cur, end);
+ fully_mapped = false;
tight = false;
} else if (map->m_flags & EROFS_MAP_FRAGMENT) {
erofs_off_t fpos = offset + cur - map->m_la;
@@ -1009,6 +1010,9 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
tight = (bs == PAGE_SIZE);
}
} while ((end = cur) > 0);
+
+ if (fully_mapped)
+ folio_set_mappedtodisk(folio);
erofs_onlinefolio_end(folio, err);
return err;
}