[PATCH RESEND 2/9] f2fs: compress: abort on read error in prepare_compress_overwrite()

[Jan Prusakowski <jprusakowski@google.com>]

prepare_compress_overwrite() reads the existing pages of a compressed
cluster before they are partially overwritten. If a folio is still not
uptodate after the read, the function releases everything and restarts
from the beginning.

When the read failed because of a persistent device I/O error (e.g.
dm-error in generic/250 and generic/252), every retry fails the same
way. Commit 3147ee567dd9 ("f2fs: fix potential deadloop in
prepare_compress_overwrite()") bounded this loop with
f2fs_handle_page_eio(), so after MAX_RETRY_PAGE_EIO attempts checkpoint
is stopped with STOP_CP_REASON_READ_DATA. As a result, a read error in a
single data cluster shuts down the whole filesystem instead of failing
the write with -EIO.

Return -EIO as soon as a folio is found not uptodate. Keep calling
f2fs_handle_page_eio(), so that repeated failures on the same page
across calls (e.g. from background writeback) still stop checkpoint as
before. Both callers already handle errors: f2fs_write_begin() fails the
write, and f2fs_write_cache_pages() stops writeback of the inode and
returns the error, leaving the pages dirty.

A folio that disappeared because of truncation (filemap_lock_folio()
fails) still restarts via release_and_retry, which is now a separate
error path after the success return.

While at it, unlock the folios in cc->rpages before dropping our
references to them in both error paths, so that a folio is never
touched after its reference is released, and drop the check of ret
before the success return, which is always true at that point.

Fixes: 4c8ff7095bef ("f2fs: support data compression")
Assisted-by: LLM
Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
---
 fs/f2fs/compress.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 9453254ff522..c5758da7c621 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1160,23 +1160,27 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
 
 		if (!folio_test_uptodate(folio)) {
 			f2fs_handle_page_eio(sbi, folio->index, DATA);
-release_and_retry:
-			f2fs_put_rpages(cc);
+			ret = -EIO;
+			/* folio i has been added to cc->rpages as well */
 			f2fs_unlock_rpages(cc, i + 1);
-			f2fs_destroy_compress_ctx(cc, true);
-			goto retry;
+			goto put_pages;
 		}
 	}
 
-	if (likely(!ret)) {
-		*fsdata = cc->rpages;
-		*pagep = cc->rpages[offset_in_cluster(cc, index)];
-		return cc->cluster_size;
-	}
+	*fsdata = cc->rpages;
+	*pagep = cc->rpages[offset_in_cluster(cc, index)];
+	return cc->cluster_size;
 
-unlock_pages:
+release_and_retry:
+	f2fs_unlock_rpages(cc, i);
 	f2fs_put_rpages(cc);
+	f2fs_destroy_compress_ctx(cc, true);
+	goto retry;
+
+unlock_pages:
 	f2fs_unlock_rpages(cc, i);
+put_pages:
+	f2fs_put_rpages(cc);
 	f2fs_destroy_compress_ctx(cc, true);
 out:
 	return ret;
-- 
2.56.0.567.gdb80ae8cd5-goog