reorganize code and add an unit test

src/overlaybd/tar/erofs/erofs_common.cpp

@@ -0,0 +1,390 @@
+/*
+   Copyright The Overlaybd Authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+	   http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+#include "erofs_common.h"
+#include <photon/common/alog.h>
+
+ssize_t ErofsCache::write_sector(u64 addr, char *buf)
+{
+	struct liberofs_inmem_sector *sector;
+
+	if (addr & (SECTOR_SIZE-1)) {
+		LOG_ERROR("Invalid addr, should be aligned to SECTOR_SIZE.");
+		return -1;
+	}
+	if (caches.find(addr) != caches.end()) {
+		sector = caches[addr];
+		memcpy(sector->data, buf, SECTOR_SIZE);
+		dirty.insert(addr);
+	} else {
+		if (caches.size() == capacity) {
+			auto it = caches.begin();
+			if (dirty.find(it->first) != dirty.end()) {
+				if (file->pwrite(it->second->data, SECTOR_SIZE, it->first)
+				    != SECTOR_SIZE)
+				{
+					LOG_ERROR("Fail to write sector %lld.", it->first);
+					return -EIO;
+				}
+				dirty.erase(it->first);
+			}
+			sector = it->second;
+			caches.erase(it);
+		} else  {
+			sector = (struct liberofs_inmem_sector*)malloc(
+					sizeof(struct liberofs_inmem_sector));
+			if (!sector)
+				return -ENOMEM;
+		}
+		memcpy(sector->data, buf, SECTOR_SIZE);
+		caches[addr] = sector;
+		dirty.insert(addr);
+	}
+	return SECTOR_SIZE;
+}
+
+ssize_t ErofsCache::read_sector(u64 addr, char *buf)
+{
+	struct liberofs_inmem_sector *sector;
+
+	if (addr & (SECTOR_SIZE - 1)) {
+		LOG_ERROR("Invalid addr, should be aligned to SECTOR_SIZE.");
+		return -1;
+	}
+
+	if (caches.find(addr) != caches.end()) {
+		sector = caches[addr];
+		memcpy(buf, sector->data, SECTOR_SIZE);
+	} else {
+		if (caches.size() == capacity) {
+			auto it = caches.begin();
+			if (dirty.find(it->first) != dirty.end()) {
+				sector = it->second;
+				if (file->pwrite(sector->data, SECTOR_SIZE, it->first)
+					!= SECTOR_SIZE)
+				{
+					LOG_ERROR("Fail to write sector %lld.", it->first);
+					return -EIO;
+				}
+				dirty.erase(it->first);
+			}
+			sector = it->second;
+			caches.erase(it);
+		} else {
+			sector = (struct liberofs_inmem_sector*)malloc(
+					sizeof(struct liberofs_inmem_sector));
+			if (!sector)
+				return -ENOMEM;
+		}
+		if (file->pread(sector->data, SECTOR_SIZE, addr) != SECTOR_SIZE) {
+			LOG_ERROR("Fail to read sector %lld", addr);
+			return -EIO;
+		}
+		caches[addr] = sector;
+		memcpy(buf, sector->data, SECTOR_SIZE);
+	}
+	return SECTOR_SIZE;
+}
+
+int ErofsCache::flush()
+{
+	for (auto it = caches.begin(); it != caches.end();) {
+		if (dirty.find(it->first) != dirty.end()) {
+			if (file->pwrite(it->second->data, SECTOR_SIZE, it->first)
+			    != SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to flush sector %lld.\n", it->first);
+				return -1;
+			}
+			dirty.erase(it->first);
+		}
+		free(it->second);
+		it = caches.erase(it);
+	}
+	return dirty.size() != 0 || caches.size() != 0;
+}
+
+/*
+ * Helper function for reading from the photon file, since
+ * the photon file requires reads to be 512-byte aligned.
+ */
+ssize_t erofs_read_photon_file(void *buf, u64 offset, size_t len,
+			       ErofsCache *cache)
+{
+
+	ssize_t read;
+	u64 start, end;
+	char extra_buf[SECTOR_SIZE];
+	u64 i, j;
+
+	start = round_down_blk(offset);
+	end = round_up_blk(offset + len);
+	read = 0;
+
+	/* we use the extra_buf to store the first sector or last sector when:
+	 * - start != offset
+	 * or
+	 * - end != offset + len
+	 */
+	if (start != offset || end != offset + len) {
+		i = start == offset ? start : start + SECTOR_SIZE;
+		j = end == offset + len ? end : end - SECTOR_SIZE;
+
+		/* read the first sector */
+		if (i != start) {
+			if (cache->read_sector(start, extra_buf) != SECTOR_SIZE) {
+				LOG_ERROR("Fail to read start sector.");
+				return -1;
+			}
+			memcpy((char*)buf, extra_buf + offset - start,
+						erofs_min(start + SECTOR_SIZE - offset,len));
+			read += erofs_min(start + SECTOR_SIZE - offset,len);
+		}
+
+		/* read the last sector and avoid re-reading the same sector as above */
+		if (j != end && (i == start || end - start > SECTOR_SIZE)) {
+			if (cache->read_sector(end - SECTOR_SIZE,
+				extra_buf) != SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to read start sector.");
+				return -1;
+			}
+			memcpy((char*)buf + end - SECTOR_SIZE - offset, extra_buf,
+					len + offset + SECTOR_SIZE - end);
+			read += len + offset + SECTOR_SIZE - end;
+		}
+
+		for (u64 addr = i; addr < j; addr += SECTOR_SIZE) {
+			if (cache->read_sector(addr,
+					       addr - offset + (char*)buf) != SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to read sector %lld in read_photo_file.\n", i);
+				return -1;
+			}
+			read += SECTOR_SIZE;
+		}
+	} else {
+		/* if read request is sector-aligned, we use the original buffer */
+		for (u64 i = start; i < end; i += SECTOR_SIZE) {
+			if (cache->read_sector(i, (char*)buf + i - start) != SECTOR_SIZE) {
+				LOG_ERROR("Fail to read start sector.");
+				return -1;
+			}
+			read += SECTOR_SIZE;
+		}
+	}
+
+	return read;
+}
+
+/*
+ * Helper function for writing to a photon file.
+ */
+ssize_t erofs_write_photon_file(const void *buf, u64 offset,
+				size_t len, ErofsCache *cache)
+ {
+	ssize_t write;
+	u64 start, end;
+	char extra_buf[SECTOR_SIZE];
+	u64 i, j;
+
+	start = round_down_blk(offset);
+	end = round_up_blk(offset + len);
+	write = 0;
+
+	if (start != offset || end != offset + len) {
+		i = start == offset ? start : start + SECTOR_SIZE;
+		j = end == offset + len ? end : end - SECTOR_SIZE;
+
+		if (i != start) {
+			if (cache->read_sector(start, extra_buf) != SECTOR_SIZE) {
+				LOG_ERROR("Fail to read sector %lld.\n", start);
+				return -1;
+			}
+			memcpy(extra_buf + offset - start, buf,
+			       erofs_min(start +  SECTOR_SIZE - offset, len));
+			if (cache->write_sector(start, extra_buf) != SECTOR_SIZE) {
+				LOG_ERROR("Fail to write sector %lld\n", start);
+				return -1;
+			}
+			write += erofs_min(start +  SECTOR_SIZE - offset, len);
+		}
+
+		if (j != end && (i == start || end - start > SECTOR_SIZE)) {
+			if (cache->read_sector(end - SECTOR_SIZE, extra_buf)
+				!= SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to read sector %lld.", end - SECTOR_SIZE);
+				return -1;
+			}
+			memcpy(extra_buf, (char*)buf + end - SECTOR_SIZE - offset,
+			       offset + len + SECTOR_SIZE - end);
+			if (cache->write_sector(end - SECTOR_SIZE, extra_buf)
+				!= SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to write sector %lld.", end - SECTOR_SIZE);
+				return -1;
+			}
+			write += offset + len + SECTOR_SIZE - end;
+		}
+
+		for (u64 addr = i; addr < j; addr += SECTOR_SIZE) {
+			if (cache->write_sector(addr, (char*)buf + addr - offset)
+				!= SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to write sector %lld.", addr);
+				return -1;
+			}
+			write += SECTOR_SIZE;
+		}
+	} else {
+		for (u64 addr = start; addr < end; addr += SECTOR_SIZE) {
+			if (cache->write_sector(addr, (char *)buf + addr - start)
+			    != SECTOR_SIZE)
+			{
+				LOG_ERROR("Fail to write sector %lld.", addr);
+				return -1;
+			}
+			write += SECTOR_SIZE;
+		}
+	}
+
+	return write;
+}
+
+/* I/O control for target */
+ssize_t erofs_target_pread(struct erofs_vfile *vf, void *buf, u64 offset,
+			   size_t len)
+{
+	struct liberofs_file *target_file =
+			reinterpret_cast<struct liberofs_file *>(vf->ops);
+
+	if (!target_file)
+		return -EINVAL;
+	if (erofs_read_photon_file(buf, offset, len, target_file->cache)
+							   != (ssize_t)len)
+		return -1;
+
+	return len;
+}
+
+ssize_t erofs_target_pwrite(struct erofs_vfile *vf, const void *buf,
+			    u64 offset, size_t len)
+{
+	struct liberofs_file *target_file =
+			reinterpret_cast<struct liberofs_file *>(vf->ops);
+
+	if (!target_file)
+		return -EINVAL;
+	if (!buf)
+		return -EINVAL;
+
+	return erofs_write_photon_file(buf, offset, len, target_file->cache);
+}
+
+int erofs_target_fsync(struct erofs_vfile *vf)
+{
+	struct liberofs_file *target_file =
+			reinterpret_cast<struct liberofs_file *>(vf->ops);
+
+	if (!target_file)
+		return -EINVAL;
+	return target_file->cache->flush();
+}
+
+int erofs_target_fallocate(struct erofs_vfile *vf, u64 offset,
+			   size_t len, bool pad)
+{
+	static const char zero[4096] = {0};
+	ssize_t ret;
+
+	while (len > 4096) {
+		ret = erofs_target_pwrite(vf, zero, offset, 4096);
+		if (ret)
+			return ret;
+		len -= 4096;
+		offset += 4096;
+	}
+	ret = erofs_target_pwrite(vf, zero, offset, len);
+	if (ret != (ssize_t)len) {
+		return -1;
+	}
+	return 0;
+}
+
+int erofs_target_ftruncate(struct erofs_vfile *vf, u64 length)
+{
+	return 0;
+}
+
+ssize_t erofs_target_read(struct erofs_vfile *vf, void *buf, size_t len)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+off_t erofs_target_lseek(struct erofs_vfile *vf, u64 offset, int whence)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+/* I/O control for source */
+ssize_t erofs_source_pread(struct erofs_vfile *vf, void *buf, u64 offset,
+			   size_t len)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+ssize_t erofs_source_pwrite(struct erofs_vfile *vf, const void *buf,
+			    u64 offset, size_t len)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+int erofs_source_fsync(struct erofs_vfile *vf)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+int erofs_source_fallocate(struct erofs_vfile *vf,
+			   u64 offset, size_t len, bool pad)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+int erofs_source_ftruncate(struct erofs_vfile *vf, u64 length)
+{
+	return -EROFS_UNIMPLEMENTED;
+}
+
+ssize_t erofs_source_read(struct erofs_vfile *vf, void *buf,
+			  size_t bytes)
+{
+	struct liberofs_file *source_file =
+			reinterpret_cast<struct liberofs_file *>(vf->ops);
+
+	if (!source_file)
+		return -EINVAL;
+	return source_file->file->read(buf, bytes);
+}
+
+off_t erofs_source_lseek(struct erofs_vfile *vf, u64 offset, int whence)
+{
+	struct liberofs_file *source_file =
+			reinterpret_cast<struct liberofs_file *>(vf->ops);
+	if (!source_file)
+		return -EINVAL;
+	return source_file->file->lseek(offset, whence);
+}