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authorUlrich Drepper <drepper@redhat.com>2006-01-18 17:43:53 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-18 19:20:29 -0800
commit5590ff0d5528b60153c0b4e7b771472b5a95e297 (patch)
tree5fdccf2354269702f71beb8e0a2942e4167fd992 /include/linux/fcntl.h
parente2f99018eb7b29954747a2dd78e9fc0c36a60f0f (diff)
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[PATCH] vfs: *at functions: core
Here is a series of patches which introduce in total 13 new system calls which take a file descriptor/filename pair instead of a single file name. These functions, openat etc, have been discussed on numerous occasions. They are needed to implement race-free filesystem traversal, they are necessary to implement a virtual per-thread current working directory (think multi-threaded backup software), etc. We have in glibc today implementations of the interfaces which use the /proc/self/fd magic. But this code is rather expensive. Here are some results (similar to what Jim Meyering posted before). The test creates a deep directory hierarchy on a tmpfs filesystem. Then rm -fr is used to remove all directories. Without syscall support I get this: real 0m31.921s user 0m0.688s sys 0m31.234s With syscall support the results are much better: real 0m20.699s user 0m0.536s sys 0m20.149s The interfaces are for obvious reasons currently not much used. But they'll be used. coreutils (and Jeff's posixutils) are already using them. Furthermore, code like ftw/fts in libc (maybe even glob) will also start using them. I expect a patch to make follow soon. Every program which is walking the filesystem tree will benefit. Signed-off-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@ftp.linux.org.uk> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux/fcntl.h')
-rw-r--r--include/linux/fcntl.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 8a7c821..c52a637 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -23,6 +23,13 @@
#define DN_ATTRIB 0x00000020 /* File changed attibutes */
#define DN_MULTISHOT 0x80000000 /* Don't remove notifier */
+#define AT_FDCWD -100 /* Special value used to indicate
+ openat should use the current
+ working directory. */
+#define AT_SYMLINK_NOFOLLOW 0x100 /* Do not follow symbolic links. */
+#define AT_REMOVEDIR 0x200 /* Remove directory instead of
+ unlinking file. */
+
#ifdef __KERNEL__
#ifndef force_o_largefile