Messages in this thread Patch in this message | | | From | Linus Torvalds <> | Date | Thu, 8 Mar 2012 19:40:47 -0800 | Subject | Re: [PATCH 3/3] sysfs: Remove SYSFS_FLAG_REMOVED and use sd->s_nlink == 0 instead. |
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Is this safe?
What's the serialization with sysfs_link_sibling(), which you just made do
sd->s_nlink++; if (!sd->s_nlink) sd->s_nlink = 1;
in your previous patch?
Yes, sysfs_link_sibling() runs under sysfs_mutex, but sysfs_dentry_delete() does not.
So what protects sysfs_dentry_delete() from never seeing that bogus 0 due to the overflow?
Linus
On Thu, Mar 8, 2012 at 1:37 PM, Eric W. Biederman <ebiederm@xmission.com> wrote: > > Now that we have a nlink field in sysfs_dirent report deleted > files and directories the traditional way with nlink == 0. > > Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> > --- > fs/sysfs/dir.c | 11 +++++------ > fs/sysfs/sysfs.h | 1 - > 2 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index 1526567..b5471d1 100644 > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -202,7 +202,7 @@ static void sysfs_deactivate(struct sysfs_dirent *sd) > DECLARE_COMPLETION_ONSTACK(wait); > int v; > > - BUG_ON(!(sd->s_flags & SYSFS_FLAG_REMOVED)); > + BUG_ON(sd->s_nlink != 0); > > if (!(sysfs_type(sd) & SYSFS_ACTIVE_REF)) > return; > @@ -279,7 +279,7 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) > static int sysfs_dentry_delete(const struct dentry *dentry) > { > struct sysfs_dirent *sd = dentry->d_fsdata; > - return !!(sd->s_flags & SYSFS_FLAG_REMOVED); > + return sd->s_nlink == 0; > } > > static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd) > @@ -294,7 +294,7 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd) > mutex_lock(&sysfs_mutex); > > /* The sysfs dirent has been deleted */ > - if (sd->s_flags & SYSFS_FLAG_REMOVED) > + if (sd->s_nlink == 0) > goto out_bad; > > /* The sysfs dirent has been moved? */ > @@ -534,7 +534,7 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) > { > struct sysfs_inode_attrs *ps_iattr; > > - BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED); > + BUG_ON(sd->s_nlink == 0); > > sysfs_unlink_sibling(sd); > > @@ -546,7 +546,6 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) > } > > sd->s_nlink = 0; > - sd->s_flags |= SYSFS_FLAG_REMOVED; > sd->u.removed_list = acxt->removed; > acxt->removed = sd; > } > @@ -946,7 +945,7 @@ static struct sysfs_dirent *sysfs_dir_pos(const void *ns, > struct sysfs_dirent *parent_sd, loff_t hash, struct sysfs_dirent *pos) > { > if (pos) { > - int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) && > + int valid = (pos->s_nlink > 0) && > pos->s_parent == parent_sd && > hash == pos->s_hash; > sysfs_put(pos); > diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h > index 71f9bf7..db2c5c5 100644 > --- a/fs/sysfs/sysfs.h > +++ b/fs/sysfs/sysfs.h > @@ -98,7 +98,6 @@ struct sysfs_dirent { > #define SYSFS_NS_TYPE_SHIFT 4 > > #define SYSFS_FLAG_MASK ~(SYSFS_NS_TYPE_MASK|SYSFS_TYPE_MASK) > -#define SYSFS_FLAG_REMOVED 0x080 > > static inline unsigned int sysfs_type(struct sysfs_dirent *sd) > { > -- > 1.7.2.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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