vfs: support caching symlink lengths in inodes

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When utilized it dodges strlen() in vfs_readlink(), giving about 1.5%
speed up when issuing readlink on /initrd.img on ext4.

Filesystems opt in by calling inode_set_cached_link() when creating an
inode.

The size is stored in a new union utilizing the same space as i_devices,
thus avoiding growing the struct or taking up any more space.

Churn-wise the current readlink_copy() helper is patched to accept the
size instead of calculating it.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20241120112037.822078-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

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Mateusz Guzik 2024-11-20 12:20:34 +01:00 • committed by Christian Brauner

parent 135ec43eb2

commit ea38219907

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4 changed files with 34 additions and 19 deletions

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34

fs/namei.c

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2

fs/proc/namespaces.c

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15

include/linux/fs.h

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2

security/apparmor/apparmorfs.c

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