[PATCH v3] erofs-utils: fix the erofs_io_pread and erofs_io_pwrite

[Hongzhen Luo]

When `vf->ops` is not null, `vf->ops->pread` returns the
number of bytes successfully read, which is inconsistent
with the semantics of `erofs_io_pread`. Similar situation
occurs in `erofs_io_pwrite`. This fixes this issue.

This also fixes `erofs_dev_close`.

Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
v2: https://lore.kernel.org/all/20240618093843.912278-1-hongzhen@linux.alibaba.com/
v1: https://lore.kernel.org/all/20240617023433.3446706-1-hongzhen@linux.alibaba.com/
---
 include/erofs/internal.h |  5 ++++-
 lib/io.c                 | 47 ++++++++++++++++++++++++++++++----------
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index f8a01ce..dfbd958 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -460,7 +460,10 @@ ssize_t erofs_dev_read(struct erofs_sb_info *sbi, int device_id,
 static inline int erofs_dev_write(struct erofs_sb_info *sbi, const void *buf,
 				  u64 offset, size_t len)
 {
-	return erofs_io_pwrite(&sbi->bdev, buf, offset, len);
+	ssize_t ret;
+
+	ret = erofs_io_pwrite(&sbi->bdev, buf, offset, len);
+	return (size_t)ret == len ? 0 : -EIO;
 }
 
 static inline int erofs_dev_fillzero(struct erofs_sb_info *sbi, u64 offset,
diff --git a/lib/io.c b/lib/io.c
index c523f00..3417b46 100644
--- a/lib/io.c
+++ b/lib/io.c
@@ -30,6 +30,7 @@ ssize_t erofs_io_pwrite(struct erofs_vfile *vf, const void *buf,
 			u64 pos, size_t len)
 {
 	ssize_t ret;
+	size_t write = 0;
 
 	if (unlikely(cfg.c_dry_run))
 		return 0;
@@ -51,9 +52,10 @@ ssize_t erofs_io_pwrite(struct erofs_vfile *vf, const void *buf,
 		len -= ret;
 		buf += ret;
 		pos += ret;
+		write += ret;
 	} while (len);
 
-	return 0;
+	return write;
 }
 
 int erofs_io_fsync(struct erofs_vfile *vf)
@@ -92,13 +94,15 @@ ssize_t erofs_io_fallocate(struct erofs_vfile *vf, u64 offset,
 		return 0;
 #endif
 	while (len > EROFS_MAX_BLOCK_SIZE) {
-		ret = erofs_io_pwrite(vf, zero, offset, EROFS_MAX_BLOCK_SIZE);
+		ret = erofs_io_pwrite(vf, zero, offset,
+			EROFS_MAX_BLOCK_SIZE) == EROFS_MAX_BLOCK_SIZE ?
+			0 : -EIO;
 		if (ret)
 			return ret;
 		len -= EROFS_MAX_BLOCK_SIZE;
 		offset += EROFS_MAX_BLOCK_SIZE;
 	}
-	return erofs_io_pwrite(vf, zero, offset, len);
+	return erofs_io_pwrite(vf, zero, offset, len) == len ? 0 : -EIO;
 }
 
 int erofs_io_ftruncate(struct erofs_vfile *vf, u64 length)
@@ -126,6 +130,7 @@ int erofs_io_ftruncate(struct erofs_vfile *vf, u64 length)
 ssize_t erofs_io_pread(struct erofs_vfile *vf, void *buf, u64 pos, size_t len)
 {
 	ssize_t ret;
+	ssize_t read = 0;
 
 	if (unlikely(cfg.c_dry_run))
 		return 0;
@@ -142,9 +147,7 @@ ssize_t erofs_io_pread(struct erofs_vfile *vf, void *buf, u64 pos, size_t len)
 #endif
 		if (ret <= 0) {
 			if (!ret) {
-				erofs_info("reach EOF of device");
-				memset(buf, 0, len);
-				return 0;
+				return read;
 			}
 			if (errno != EINTR) {
 				erofs_err("failed to read: %s", strerror(errno));
@@ -155,8 +158,11 @@ ssize_t erofs_io_pread(struct erofs_vfile *vf, void *buf, u64 pos, size_t len)
 		pos += ret;
 		len -= ret;
 		buf += ret;
+		read += ret;
+
 	} while (len);
-	return 0;
+
+	return read;
 }
 
 static int erofs_get_bdev_size(int fd, u64 *bytes)
@@ -287,7 +293,8 @@ out:
 
 void erofs_dev_close(struct erofs_sb_info *sbi)
 {
-	close(sbi->bdev.fd);
+	if (!sbi->bdev.ops)
+		close(sbi->bdev.fd);
 	free(sbi->devname);
 	sbi->devname = NULL;
 	sbi->bdev.fd = -1;
@@ -320,11 +327,29 @@ int erofs_blob_open_ro(struct erofs_sb_info *sbi, const char *dev)
 ssize_t erofs_dev_read(struct erofs_sb_info *sbi, int device_id,
 		       void *buf, u64 offset, size_t len)
 {
-	if (device_id)
-		return erofs_io_pread(&((struct erofs_vfile) {
+	ssize_t ret;
+
+	if (device_id) {
+		ret = erofs_io_pread(&((struct erofs_vfile) {
 				.fd = sbi->blobfd[device_id - 1],
 			}), buf, offset, len);
-	return erofs_io_pread(&sbi->bdev, buf, offset, len);
+		if (ret < 0)
+			return ret;
+		if (ret < len) {
+			erofs_info("reach EOF of device");
+			memset(buf + ret, 0, len - ret);
+		}
+		return 0;
+	}
+
+	ret = erofs_io_pread(&sbi->bdev, buf, offset, len);
+	if (ret < 0)
+		return ret;
+	if (ret < len) {
+		erofs_info("reach EOF of device");
+		memset(buf + ret, 0, len - ret);
+	}
+	return 0;
 }
 
 static ssize_t __erofs_copy_file_range(int fd_in, u64 *off_in,
-- 
2.39.3