Commit d4c5e960 authored Nov 28, 2019 by Theodore Ts'o

ext4: avoid fetching btime in ext4_getattr() unless requested

Linus observed that an allmodconfig build which does a lot of stat(2)
calls that ext4_getattr() was a noticeable (1%) amount of CPU time,
due to the cache line for i_extra_isize getting pulled in.  Since the
normal stat system call doesn't return btime, it's a complete waste.
So only calculate btime when it is explicitly requested.

[ Fixed to check against request_mask instead of query_flags. ]

Link: https://lore.kernel.org/r/CAHk-=wivmk_j6KbTX+Er64mLrG8abXZo0M10PNdAnHc8fWXfsQ@mail.gmail.com


Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent 8cd115bd

fs/ext4/inode.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5399,7 +5399,8 @@ int ext4_getattr(const struct path path, struct kstat stat,
		struct ext4_inode_info *ei = EXT4_I(inode);
		unsigned int flags;

		if (EXT4_FITS_IN_INODE(raw_inode, ei, i_crtime)) {
		if ((request_mask & STATX_BTIME) &&
		EXT4_FITS_IN_INODE(raw_inode, ei, i_crtime)) {
		stat->result_mask \|= STATX_BTIME;
		stat->btime.tv_sec = ei->i_crtime.tv_sec;
		stat->btime.tv_nsec = ei->i_crtime.tv_nsec;

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