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Subject[PATCH 10/26] sysfs: Optimize just changing the sysfs file mode.
From: Eric W. Biederman <ebiederm@xmission.com>

Don't allocate a struct iattr for the sysfs dentry if just
the mode changes because we have a field for that on the
sysfs_dirent, and we can trigger that case with sysfs_chmod_file.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---
fs/sysfs/inode.c | 22 ++++++++++++++--------
1 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 555f0ff..70ff2a2 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -60,12 +60,16 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
return error;

iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
+ if (iattr->ia_valid & ATTR_MODE) {
+ if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+ iattr->ia_mode &= ~S_ISGID;
+ }

error = inode_setattr(inode, iattr);
if (error)
return error;

- if (!sd_iattr) {
+ if (!sd_iattr && (ia_valid & ~ATTR_MODE)) {
/* setting attributes for the first time, allocate now */
sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
if (!sd_iattr)
@@ -78,6 +82,13 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
sd->s_iattr = sd_iattr;
}

+ if (ia_valid & ATTR_MODE)
+ sd->s_mode = iattr->ia_mode;
+
+ /* If we don't need the extra attributes leave */
+ if (!sd_iattr)
+ return 0;
+
/* attributes were changed atleast once in past */

if (ia_valid & ATTR_UID)
@@ -93,13 +104,8 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
if (ia_valid & ATTR_CTIME)
sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
inode->i_sb->s_time_gran);
- if (ia_valid & ATTR_MODE) {
- umode_t mode = iattr->ia_mode;
-
- if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
- mode &= ~S_ISGID;
- sd_iattr->ia_mode = sd->s_mode = mode;
- }
+ if (ia_valid & ATTR_MODE)
+ sd_iattr->ia_mode = iattr->ia_mode;

return error;
}
--
1.6.3.1.54.g99dd.dirty


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