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[PATCH] knfsd: reduce stack consumption

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A typical nfsd call trace is
 nfsd -> svc_process -> nfsd_dispatch -> nfsd3_proc_write ->
   nfsd_write ->nfsd_vfs_write -> vfs_writev

These add up to over 300 bytes on the stack.
Looking at each of these, I see that nfsd_write (which includes
 nfsd_vfs_write) contributes 0x8c to stack usage itself!!

It turns out this is because it puts a 'struct iattr' on the stack so
it can kill suid if needed.  The following patch saves about 50 bytes
off the stack in this call path.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Neil Brown 2006-01-06 00:19:59 -08:00 committed by Linus Torvalds
parent a334de2866
commit 9f708e40fe
1 changed files with 12 additions and 8 deletions
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20
fs/nfsd/vfs.c
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@ -880,6 +880,16 @@ out:
return err;
}
static void kill_suid(struct dentry *dentry)
{
struct iattr ia;
ia.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID;
down(&dentry->d_inode->i_sem);
notify_change(dentry, &ia);
up(&dentry->d_inode->i_sem);
}
static inline int
nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
loff_t offset, struct kvec *vec, int vlen,
@ -933,14 +943,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
}
/* clear setuid/setgid flag after write */
if (err >= 0 && (inode->i_mode & (S_ISUID | S_ISGID))) {
struct iattr ia;
ia.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID;
down(&inode->i_sem);
notify_change(dentry, &ia);
up(&inode->i_sem);
}
if (err >= 0 && (inode->i_mode & (S_ISUID | S_ISGID)))
kill_suid(dentry);
if (err >= 0 && stable) {
static ino_t last_ino;