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android_packages_modules_Virtualization
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zipfuse: optimize for uncompressed zip entries 

Previously, when a zip entry is opened, its entire content was copied
into zipfuse and kept there until the file is closed. This is a waste of
memory because if the zip entry is stored uncompressed, it can be
directly read from the containing zip file.

This CL implements the optimization.

Bug: 187878241
Test: atest zipfuse.test
Change-Id: Ia2d516d4d03d699ee7da72f576f337bd73516427
This commit is contained in:
Jiyong Park 2021-08-30 22:32:19 +09:00
parent adc38d1e55
commit f5ff33cf49
3 changed files with 86 additions and 28 deletions
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2
zipfuse/Android.bp
View File

@ -14,6 +14,8 @@ rust_defaults {
"libfuse_rust",
"liblibc",
"libzip",
"libscopeguard",
"liblog_rust",
],
// libfuse_rust, etc don't support 32-bit targets
multilib: {

3
zipfuse/Cargo.toml
View File

@ -12,7 +12,8 @@ libc = "0.2"
zip = "0.5"
tempfile = "3.2"
nix = "0.20"
scopeguard = "1.1"
log = "0.4"
[dev-dependencies]
loopdev = "0.2"
scopeguard = "1.1"

101
zipfuse/src/main.rs
View File

@ -87,20 +87,23 @@ pub fn run_fuse(zip_file: &Path, mount_point: &Path, extra_options: Option<&str>
struct ZipFuse {
zip_archive: Mutex<zip::ZipArchive<File>>,
raw_file: Mutex<File>,
inode_table: InodeTable,
open_files: Mutex<HashMap<Handle, OpenFileBuf>>,
open_files: Mutex<HashMap<Handle, OpenFile>>,
open_dirs: Mutex<HashMap<Handle, OpenDirBuf>>,
}
/// Holds the (decompressed) contents of a [`ZipFile`].
///
/// This buf is needed because `ZipFile` is in general not seekable due to the compression.
///
/// TODO(jiyong): do this only for compressed `ZipFile`s. Uncompressed (store) files don't need
/// this; they can be directly read from `zip_archive`.
struct OpenFileBuf {
/// Represents a [`ZipFile`] that is opened.
struct OpenFile {
open_count: u32, // multiple opens share the buf because this is a read-only filesystem
buf: Box<[u8]>,
content: OpenFileContent,
}
/// Holds the content of a [`ZipFile`]. Depending on whether it is compressed or not, the
/// entire content is stored, or only the zip index is stored.
enum OpenFileContent {
Compressed(Box<[u8]>),
Uncompressed(usize), // zip index
}
/// Holds the directory entries in a directory opened by [`opendir`].
@ -123,11 +126,15 @@ impl ZipFuse {
fn new(zip_file: &Path) -> Result<ZipFuse> {
// TODO(jiyong): Use O_DIRECT to avoid double caching.
// `.custom_flags(nix::fcntl::OFlag::O_DIRECT.bits())` currently doesn't work.
let f = OpenOptions::new().read(true).open(zip_file)?;
let f = File::open(zip_file)?;
let mut z = zip::ZipArchive::new(f)?;
// Open the same file again so that we can directly access it when accessing
// uncompressed zip_file entries in it. `ZipFile` doesn't implement `Seek`.
let raw_file = File::open(zip_file)?;
let it = InodeTable::from_zip(&mut z)?;
Ok(ZipFuse {
zip_archive: Mutex::new(z),
raw_file: Mutex::new(raw_file),
inode_table: it,
open_files: Mutex::new(HashMap::new()),
open_dirs: Mutex::new(HashMap::new()),
@ -208,21 +215,37 @@ impl fuse::filesystem::FileSystem for ZipFuse {
// If the file is already opened, just increase the reference counter. If not, read the
// entire file content to the buffer. When `read` is called, a portion of the buffer is
// copied to the kernel.
// TODO(jiyong): do this only for compressed zip files. Files that are not compressed
// (store) can be directly read from zip_archive. That will help reduce the memory usage.
if let Some(ofb) = open_files.get_mut(&handle) {
if ofb.open_count == 0 {
if let Some(file) = open_files.get_mut(&handle) {
if file.open_count == 0 {
return Err(ebadf());
}
ofb.open_count += 1;
file.open_count += 1;
} else {
let inode_data = self.find_inode(inode)?;
let zip_index = inode_data.get_zip_index().ok_or_else(ebadf)?;
let mut zip_archive = self.zip_archive.lock().unwrap();
let mut zip_file = zip_archive.by_index(zip_index)?;
let content = match zip_file.compression() {
zip::CompressionMethod::Stored => OpenFileContent::Uncompressed(zip_index),
_ => {
if let Some(mode) = zip_file.unix_mode() {
let is_reg_file = zip_file.is_file();
let is_executable =
mode & (libc::S_IXUSR | libc::S_IXGRP | libc::S_IXOTH) != 0;
if is_reg_file && is_executable {
log::warn!(
"Executable file {:?} is stored compressed. Consider \
storing it uncompressed to save memory",
zip_file.mangled_name()
);
}
}
let mut buf = Vec::with_capacity(inode_data.size as usize);
zip_file.read_to_end(&mut buf)?;
open_files.insert(handle, OpenFileBuf { open_count: 1, buf: buf.into_boxed_slice() });
OpenFileContent::Compressed(buf.into_boxed_slice())
}
};
open_files.insert(handle, OpenFile { open_count: 1, content });
}
// Note: we don't return `DIRECT_IO` here, because then applications wouldn't be able to
// mmap the files.
@ -244,8 +267,8 @@ impl fuse::filesystem::FileSystem for ZipFuse {
// again when the same file is opened in the future.
let mut open_files = self.open_files.lock().unwrap();
let handle = inode as Handle;
if let Some(ofb) = open_files.get_mut(&handle) {
if ofb.open_count.checked_sub(1).ok_or_else(ebadf)? == 0 {
if let Some(file) = open_files.get_mut(&handle) {
if file.open_count.checked_sub(1).ok_or_else(ebadf)? == 0 {
open_files.remove(&handle);
}
Ok(())
@ -266,15 +289,28 @@ impl fuse::filesystem::FileSystem for ZipFuse {
_flags: u32,
) -> io::Result<usize> {
let open_files = self.open_files.lock().unwrap();
let ofb = open_files.get(&handle).ok_or_else(ebadf)?;
if ofb.open_count == 0 {
let file = open_files.get(&handle).ok_or_else(ebadf)?;
if file.open_count == 0 {
return Err(ebadf());
}
Ok(match &file.content {
OpenFileContent::Uncompressed(zip_index) => {
let mut zip_archive = self.zip_archive.lock().unwrap();
let zip_file = zip_archive.by_index(*zip_index)?;
let start = zip_file.data_start() + offset;
let remaining_size = zip_file.size() - offset;
let size = std::cmp::min(remaining_size, size.into());
let mut raw_file = self.raw_file.lock().unwrap();
w.write_from(&mut raw_file, size as usize, start)?
}
OpenFileContent::Compressed(buf) => {
let start = offset as usize;
let end = start + size as usize;
let end = std::cmp::min(end, ofb.buf.len());
let read_len = w.write(&ofb.buf[start..end])?;
Ok(read_len)
let end = std::cmp::min(end, buf.len());
w.write(&buf[start..end])?
}
})
}
fn opendir(
@ -672,6 +708,25 @@ mod tests {
run_fuse_and_check_test_zip(test_dir.path(), &zip_path);
}
#[test]
fn supports_store() {
run_test(
|zip| {
let data = vec![10; 2 << 20];
zip.start_file(
"foo",
FileOptions::default().compression_method(zip::CompressionMethod::Stored),
)
.unwrap();
zip.write_all(&data).unwrap();
},
|root| {
let data = vec![10; 2 << 20];
check_file(root, "foo", &data);
},
);
}
#[cfg(not(target_os = "android"))] // Android doesn't have the loopdev crate
#[test]
fn supports_zip_on_block_device() {