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We have to be able to have library in /etc/ld.so.preload without other effect on system than handling better IO on rewrited directory.

To pass cthon04, we have to implement these calls.

*stat calls does not check existence of whiteout files.

We need to have mode where cache is not generated but:

• can be used if data exist in shadow directory
• reporting data and metadata changing operations to log

We have to prepend chroot directory before $PWD because absolute path is used for IO routing deciding.

Hello,

I am trying to use libiorouter inside CI process and I am facing some issues, starting with CMake.

For the reproduce purpose I am using the default libiorouter.h with env LIBIOR_IO=on.

Steps to reproduce:

mkdir -p /tmp/cmake-test/build
cd /tmp/cmake-test/build
echo 'program(foo C CXX)' > ../CMakeLists.txt
LIBIOR_IO=on LD_PRELOAD=/path/to/libiorouter.so cmake ..

Strace output:

(...)
getcwd("/tmp/cmake-test/build", 2048)   = 22
lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=140, ...}) = 0
lstat("/tmp/cmake-test", {st_mode=S_IFDIR|0700, st_size=80, ...}) = 0
lstat("/tmp/cmake-test/build", {st_mode=S_IFDIR|0700, st_size=60, ...}) = 0
getcwd("/tmp/cmake-test/build", 4096)   = 22
access("cmake", R_OK)                   = -1 ENOENT (No such file or directory)
access("/home/piotr/bin/cmake", R_OK)   = -1 ENOENT (No such file or directory)
access("/usr/local/bin/cmake", R_OK)    = -1 ENOENT (No such file or directory)
access("/usr/bin/cmake", R_OK)          = 0
stat("/usr/bin/cmake", {st_mode=S_IFREG|0755, st_size=4508920, ...}) = 0
access("/usr/bin/cmake", R_OK)          = 0
access("/usr/bin/cmake", R_OK)          = 0
lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/bin", {st_mode=S_IFDIR|0755, st_size=69632, ...}) = 0
lstat("/usr/bin/cmake", {st_mode=S_IFREG|0755, st_size=4508920, ...}) = 0
access("/usr/bin/cmake-gui", R_OK)      = -1 ENOENT (No such file or directory)
access("/usr/bin/ccmake", R_OK)         = 0
access("/usr/share/cmake/Modules/CMake.cmake", R_OK) = 0
getcwd("/tmp/cmake-test/build", 2048)   = 22
getcwd("/tmp/cmake-test/build", 4096)   = 22
stat("..", {st_mode=S_IFDIR|0700, st_size=80, ...}) = 0
getcwd("/tmp/cmake-test/build", 2048)   = 22
access("/tmp/cmake-test/CMakeCache.txt", R_OK) = -1 ENOENT (No such file or directory)
access("/tmp/cmake-test/CMakeLists.txt", R_OK) = 0
getcwd("/tmp/cmake-test/build", 2048)   = 22
access("/tmp/cmake-test/build/CMakeCache.txt", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/tmp/cmake-test/build/CMakeFiles/", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("", 0x7ffee756d3f0)                = -1 ENOENT (No such file or directory)
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0} ---
+++ killed by SIGSEGV +++

Because files can be created by openat() function (with zero size), we have to handle situation where size of file in cache is 0, so we have to reread it again from backend storage.

We would need also rename() funcionality.

rename() would be a bit harder to implement because we have to handle varioius situations:

• src rel, dst rel
• src absolute,dst rel
• src rel, dst absolute
• src absolute,dst absolute
• renameat() variant

We have to implement hook on create() because there can be scenario where we app calls create() and then readdir() .

Without create() hook it would simply return directory from cache without created file.

xcache passes somehow our IO hook for stat, probably because it directly calls stat syscal. We have to hook PHP's zend VCWD_STAT function which is basically the same as stat().

We need CI test for directory handling because it is complex function.

Environment variables should be used to configure modes for libiorouter, cache directory or backend directory.

Because of rm -rf case, we need to have working dirfd handling.

Create series of CI (using travis-ci) tests which uses

• cthon04 framework
• xfstests suite
  to be sure, that we're not changing fundamental behaviour of called IO functions but only their speed.

Hi,

libiorouter does not seems to work at all here.

I've set env variable LIBIOR_IO=yes, I have also modified libiorouter.h:

#define DEFAULT_SOCK_PATH "/dev/shm/libiorouter.sock"
#define DEFAULT_CACHEDIR "/dev/shm/io_cache/"
#define DEFAULT_REWRITEDIR "/home/"

then I've been testing few random binaries like sh, cat or vim with LD_PRELOAD set on the new libiorouter.so, no cache has been created in /dev/shm/io_cache/, also I've notice multiple failures while opening /dev/shm/io_cache//libiorouter. After manually creating it some .stats and .journal has been created there.

When checking on /home/piotr/.zshrc one of .stats files does indeed contain

libiorouter has been inicialized.
1436981265.768451 CALL open /home/piotr/.zshrc

However there seems to not be any cache in /dev/shm/io_cache/ at all.

We should be more consistent during:

• tracking/stats
• debuging

We have to implement various *at functions such as:

• faccessat()
• fchmodat()
• fchownat()
• fstatat()
• unlinkat()

readdir is not thread safe because it is using statical buffer. We have to rewrote code to readdir_r which should be fine.

libiorouter should be distributed as a debian package.

Whiteout optimization does not work well everytime. We should be able to turn it off/on .