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ext4: Remove useless spinlock in ext4_getattr() 

Linus noted, and complained to me, that doing while lots of "git diff"'s
of kernel sources, these spinlocks were responsible for 27% of the
spinlock cost on his two-processor system as reported by perf.

Git was doing lots of parallel stats, and this was putting a lot of
pressure on ext4_getattr().  A spinlock to protect a single
memory-to-memory copy is pointless, so remove it.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Theodore Ts'o 2010-11-02 09:34:50 -04:00 committed by Linus Torvalds
parent 7fe19da4ca
commit eb8abb927a
1 changed files with 0 additions and 2 deletions
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2
fs/ext4/inode.c
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@ -5410,9 +5410,7 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
* will return the blocks that include the delayed allocation
* blocks for this file.
*/
spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
delalloc_blocks = EXT4_I(inode)->i_reserved_data_blocks;
spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
stat->blocks += (delalloc_blocks << inode->i_sb->s_blocksize_bits)>>9;
return 0;