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devfs: save on spurious relocking for devfs_populate

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Tested by:	pho
This commit is contained in:
Mateusz Guzik 2020-08-10 10:36:43 +00:00
parent f8935a96d1
commit 7b19bddac8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364069
3 changed files with 16 additions and 2 deletions
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1
sys/fs/devfs/devfs.h
View file

@ -192,6 +192,7 @@ char *devfs_fqpn(char *, struct devfs_mount *, struct devfs_dirent *,
struct componentname *);
void devfs_delete(struct devfs_mount *, struct devfs_dirent *, int);
void devfs_dirent_free(struct devfs_dirent *);
bool devfs_populate_needed(struct devfs_mount *dm);
void devfs_populate(struct devfs_mount *);
void devfs_cleanup(struct devfs_mount *);
void devfs_unmount_final(struct devfs_mount *);

11
sys/fs/devfs/devfs_devs.c
View file

@ -659,6 +659,13 @@ devfs_populate_loop(struct devfs_mount *dm, int cleanup)
return (0);
}
bool
devfs_populate_needed(struct devfs_mount *dm)
{
return (dm->dm_generation != devfs_generation);
}
/*
* The caller needs to hold the dm for the duration of the call.
*/
@ -668,9 +675,9 @@ devfs_populate(struct devfs_mount *dm)
unsigned gen;
sx_assert(&dm->dm_lock, SX_XLOCKED);
gen = devfs_generation;
if (dm->dm_generation == gen)
if (!devfs_populate_needed(dm))
return;
gen = devfs_generation;
while (devfs_populate_loop(dm, 0))
continue;
dm->dm_generation = gen;

6
sys/fs/devfs/devfs_vnops.c
View file

@ -235,6 +235,11 @@ devfs_populate_vp(struct vnode *vp)
ASSERT_VOP_LOCKED(vp, "devfs_populate_vp");
dmp = VFSTODEVFS(vp->v_mount);
if (!devfs_populate_needed(dmp)) {
sx_xlock(&dmp->dm_lock);
goto out_nopopulate;
}
locked = VOP_ISLOCKED(vp);
sx_xlock(&dmp->dm_lock);
@ -252,6 +257,7 @@ devfs_populate_vp(struct vnode *vp)
devfs_unmount_final(dmp);
return (ERESTART);
}
out_nopopulate:
if (VN_IS_DOOMED(vp)) {
sx_xunlock(&dmp->dm_lock);
return (ERESTART);