From: Yifan Zhao <[email protected]>

File-level compression fallback is control flow, not a real error.
Return an erofs-specific status code for it instead of overloading
-ENOSPC, which can also report real space failures.

Keep the global compression context reusable for that fallback while
preserving the fatal state for real errors.

Fixes: a729584ef975 ("erofs-utils: mkfs: avoid hanging if fragment is on and 
tmpdir is full")
Reported-by: Bastian Schmitz <[email protected]>
Closes: https://github.com/erofs/erofs-utils/issues/50
Assisted-by: Codex:GPT-5.5
Signed-off-by: Yifan Zhao <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
---
 include/erofs/err.h |  3 +++
 lib/compress.c      | 10 +++++++---
 lib/inode.c         |  6 +++---
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/erofs/err.h b/include/erofs/err.h
index 7dacc917a4c1..bf5a4e1cf9b7 100644
--- a/include/erofs/err.h
+++ b/include/erofs/err.h
@@ -53,6 +53,9 @@ static inline void * ERR_CAST(const void *ptr)
        return (void *) ptr;
 }
 
+/* EROFS-specific error codes */
+#define EROFS_RETCODE_FALLBACK         MAX_ERRNO
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/compress.c b/lib/compress.c
index ea07409defef..0f448e400a2d 100644
--- a/lib/compress.c
+++ b/lib/compress.c
@@ -1375,7 +1375,7 @@ int erofs_commit_compressed_file(struct 
z_erofs_compress_ictx *ictx,
            legacymetasize >= inode->i_size) {
                z_erofs_dedupe_ext_commit(true);
                z_erofs_dedupe_commit(true);
-               ret = -ENOSPC;
+               ret = EROFS_RETCODE_FALLBACK;
                goto err_free_meta;
        }
        z_erofs_dedupe_ext_commit(false);
@@ -2031,7 +2031,11 @@ err_free_idata:
 out:
 #ifdef EROFS_MT_ENABLED
        pthread_mutex_lock(&ictx->mutex);
-       ictx->seg_num = ret < 0 ? INT_MAX : 0;
+       if (ret < 0 && ret != EROFS_RETCODE_FALLBACK)
+               /* mark as failed to avoid further processing */
+               ictx->seg_num = INT_MAX;
+       else
+               ictx->seg_num = 0;
        pthread_cond_signal(&ictx->cond);
        pthread_mutex_unlock(&ictx->mutex);
 #endif
@@ -2044,7 +2048,7 @@ int erofs_begin_compress_dir(struct erofs_importer *im,
 {
        if (!im->params->compress_dir ||
            inode->i_size < Z_EROFS_LEGACY_MAP_HEADER_SIZE)
-               return -ENOSPC;
+               return EROFS_RETCODE_FALLBACK;
 
        inode->z_advise |= Z_EROFS_ADVISE_FRAGMENT_PCLUSTER;
        erofs_sb_set_fragments(inode->sbi);
diff --git a/lib/inode.c b/lib/inode.c
index c225faa121e7..4c2d094bac7e 100644
--- a/lib/inode.c
+++ b/lib/inode.c
@@ -1507,7 +1507,7 @@ static int erofs_mkfs_job_write_file(struct 
erofs_mkfs_job_ndir_ctx *ctx)
 
        if (ctx->ictx) {
                ret = erofs_write_compressed_file(ctx->ictx);
-               if (ret != -ENOSPC)
+               if (ret != EROFS_RETCODE_FALLBACK)
                        goto out;
                if (lseek(ctx->fd, ctx->fpos, SEEK_SET) < 0) {
                        ret = -errno;
@@ -1594,7 +1594,7 @@ static int erofs_mkfs_create_directory(const struct 
erofs_mkfs_btctx *ctx,
                inode->datalayout = EROFS_INODE_FLAT_INLINE;
 
                ret = erofs_begin_compress_dir(ctx->im, inode);
-               if (ret && ret != -ENOSPC)
+               if (ret && ret != EROFS_RETCODE_FALLBACK)
                        return ret;
        } else {
                DBG_BUGON(inode->datalayout != EROFS_INODE_FLAT_PLAIN);
@@ -2391,7 +2391,7 @@ struct erofs_inode 
*erofs_mkfs_build_special_from_fd(struct erofs_importer *im,
                ret = erofs_write_compressed_file(ictx);
                if (!ret)
                        goto out;
-               if (ret != -ENOSPC)
+               if (ret != EROFS_RETCODE_FALLBACK)
                         return ERR_PTR(ret);
 
                ret = lseek(fd, 0, SEEK_SET);
-- 
2.43.5


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