Commit 27917e81 authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: address D-cache aliasing 

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: 3883a79a ("staging: erofs: introduce VLE decompression support")
Closes: https://lore.kernel.org/r/c1e51e16-6cc6-49d0-a63e-4e9ff6c4dd53@pengutronix.de
Closes: https://lore.kernel.org/r/38d43fae-1182-4155-9c5b-ffc7382d9917@siemens.com


Tested-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Tested-by: default avatarStefan Kerkmann <s.kerkmann@pengutronix.de>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250709034614.2780117-2-hsiangkao@linux.alibaba.com
parent f5443d0d

fs/erofs/data.c

+11 −5
Original line number Diff line number Diff line
@@ -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,

fs/erofs/decompressor.c

+4 −8
Original line number Diff line number Diff line
@@ -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);

fs/erofs/fileio.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}

fs/erofs/internal.h

+1 −1
Original line number Diff line number Diff line
@@ -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,

fs/erofs/zdata.c

+3 −3
Original line number Diff line number Diff line
@@ -1091,7 +1091,7 @@ 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;

}
@@ -1196,7 +1196,7 @@ 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);

	}
@@ -1355,7 +1355,7 @@ 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) {