Ping on this patchset again... @Andrew: while looking through lkml archives from a lifetime ago at https://lkml.org/lkml/2008/8/16/59 , it appears that your preference at the time was to drop the scattered INITRAMFS_PRESERVE_MTIME ifdefs prior to merge. I'd much appreciate your thoughts on the reintroduction of the option based on the microbenchmark results below. On Fri, 7 Jan 2022 14:38:11 +0100, David Disseldorp wrote: > initramfs cpio mtime preservation, as implemented in commit 889d51a10712 > ("initramfs: add option to preserve mtime from initramfs cpio images"), > uses a linked list to defer directory mtime processing until after all > other items in the cpio archive have been processed. This is done to > ensure that parent directory mtimes aren't overwritten via subsequent > child creation. Contrary to the 889d51a10712 commit message, the mtime > preservation behaviour is unconditional. > > This change adds a new INITRAMFS_PRESERVE_MTIME Kconfig option, which > can be used to disable on-by-default mtime retention and in turn > speed up initramfs extraction, particularly for cpio archives with large > directory counts. > > Benchmarks with a one million directory cpio archive extracted 20 times > demonstrated: > mean extraction time (s) std dev > INITRAMFS_PRESERVE_MTIME=y 3.808 0.006 > INITRAMFS_PRESERVE_MTIME unset 3.056 0.004 > > The above extraction times were measured using ftrace > (initcall_finish - initcall_start) values for populate_rootfs() with > initramfs_async disabled. > > Signed-off-by: David Disseldorp <ddiss@xxxxxxx> > Reviewed-by: Martin Wilck <mwilck@xxxxxxxx> > [ddiss: rebase atop dir_entry.name flexible array member] > --- > init/Kconfig | 10 ++++++++ > init/initramfs.c | 50 +++------------------------------------- > init/initramfs_mtime.h | 52 ++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 65 insertions(+), 47 deletions(-) > create mode 100644 init/initramfs_mtime.h > > diff --git a/init/Kconfig b/init/Kconfig > index 4b7bac10c72d..a98f63d3c366 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1357,6 +1357,16 @@ config BOOT_CONFIG > > If unsure, say Y. > > +config INITRAMFS_PRESERVE_MTIME > + bool "Preserve cpio archive mtimes in initramfs" > + default y > + help > + Each entry in an initramfs cpio archive carries an mtime value. When > + enabled, extracted cpio items take this mtime, with directory mtime > + setting deferred until after creation of any child entries. > + > + If unsure, say Y. > + > choice > prompt "Compiler optimization level" > default CC_OPTIMIZE_FOR_PERFORMANCE > diff --git a/init/initramfs.c b/init/initramfs.c > index 656d2d71349f..5b4ca8ecadb5 100644 > --- a/init/initramfs.c > +++ b/init/initramfs.c > @@ -17,6 +17,8 @@ > #include <linux/init_syscalls.h> > #include <linux/umh.h> > > +#include "initramfs_mtime.h" > + > static ssize_t __init xwrite(struct file *file, const char *p, size_t count, > loff_t *pos) > { > @@ -116,48 +118,6 @@ static void __init free_hash(void) > } > } > > -static long __init do_utime(char *filename, time64_t mtime) > -{ > - struct timespec64 t[2]; > - > - t[0].tv_sec = mtime; > - t[0].tv_nsec = 0; > - t[1].tv_sec = mtime; > - t[1].tv_nsec = 0; > - return init_utimes(filename, t); > -} > - > -static __initdata LIST_HEAD(dir_list); > -struct dir_entry { > - struct list_head list; > - time64_t mtime; > - char name[]; > -}; > - > -static void __init dir_add(const char *name, time64_t mtime) > -{ > - size_t nlen = strlen(name) + 1; > - struct dir_entry *de; > - > - de = kmalloc(sizeof(struct dir_entry) + nlen, GFP_KERNEL); > - if (!de) > - panic_show_mem("can't allocate dir_entry buffer"); > - INIT_LIST_HEAD(&de->list); > - strscpy(de->name, name, nlen); > - de->mtime = mtime; > - list_add(&de->list, &dir_list); > -} > - > -static void __init dir_utime(void) > -{ > - struct dir_entry *de, *tmp; > - list_for_each_entry_safe(de, tmp, &dir_list, list) { > - list_del(&de->list); > - do_utime(de->name, de->mtime); > - kfree(de); > - } > -} > - > static __initdata time64_t mtime; > > /* cpio header parsing */ > @@ -381,14 +341,10 @@ static int __init do_name(void) > static int __init do_copy(void) > { > if (byte_count >= body_len) { > - struct timespec64 t[2] = { }; > if (xwrite(wfile, victim, body_len, &wfile_pos) != body_len) > error("write error"); > > - t[0].tv_sec = mtime; > - t[1].tv_sec = mtime; > - vfs_utimes(&wfile->f_path, t); > - > + do_utime_path(&wfile->f_path, mtime); > fput(wfile); > eat(body_len); > state = SkipIt; > diff --git a/init/initramfs_mtime.h b/init/initramfs_mtime.h > new file mode 100644 > index 000000000000..688ed4b6f327 > --- /dev/null > +++ b/init/initramfs_mtime.h > @@ -0,0 +1,52 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > + > +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME > +static void __init do_utime(char *filename, time64_t mtime) > +{ > + struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } }; > + init_utimes(filename, t); > +} > + > +static void __init do_utime_path(const struct path *path, time64_t mtime) > +{ > + struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } }; > + vfs_utimes(path, t); > +} > + > +static __initdata LIST_HEAD(dir_list); > +struct dir_entry { > + struct list_head list; > + time64_t mtime; > + char name[]; > +}; > + > +static void __init dir_add(const char *name, time64_t mtime) > +{ > + size_t nlen = strlen(name) + 1; > + struct dir_entry *de; > + > + de = kmalloc(sizeof(struct dir_entry) + nlen, GFP_KERNEL); > + if (!de) > + panic("can't allocate dir_entry buffer"); > + INIT_LIST_HEAD(&de->list); > + strscpy(de->name, name, nlen); > + de->mtime = mtime; > + list_add(&de->list, &dir_list); > +} > + > +static void __init dir_utime(void) > +{ > + struct dir_entry *de, *tmp; > + > + list_for_each_entry_safe(de, tmp, &dir_list, list) { > + list_del(&de->list); > + do_utime(de->name, de->mtime); > + kfree(de); > + } > +} > +#else > +static void __init do_utime(char *filename, time64_t mtime) {} > +static void __init do_utime_path(const struct path *path, time64_t mtime) {} > +static void __init dir_add(const char *name, time64_t mtime) {} > +static void __init dir_utime(void) {} > +#endif
