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Message-ID: <20091104043249.GG27639@us.ibm.com>
Date: Tue, 3 Nov 2009 22:32:49 -0600
From: "Serge E. Hallyn" <serue@...ibm.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Greg Kroah-Hartman <gregkh@...e.de>,
Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
Cornelia Huck <cornelia.huck@...ibm.com>,
linux-fsdevel@...r.kernel.org,
Eric Dumazet <eric.dumazet@...il.com>,
Benjamin LaHaise <bcrl@...et.ca>,
"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 11/13] sysfs: Gut sysfs_addrm_start and
sysfs_addrm_finish
Quoting Eric W. Biederman (ebiederm@...ssion.com):
> From: Eric W. Biederman <ebiederm@...stanetworks.com>
>
> With lazy inode updates and dentry operations bringing everything
> into sync on demand there is no longer any need to immediately
> update the vfs or grab i_mutex to protect those updates as we
> make changes to sysfs.
>
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
Acked-by: Serge Hallyn <serue@...ibm.com>
> ---
> fs/sysfs/dir.c | 91 ++---------------------------------------------------
> fs/sysfs/sysfs.h | 2 -
> 2 files changed, 4 insertions(+), 89 deletions(-)
>
> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index 25d052a..a05b027 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -386,12 +386,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
> return NULL;
> }
>
> -static int sysfs_ilookup_test(struct inode *inode, void *arg)
> -{
> - struct sysfs_dirent *sd = arg;
> - return inode->i_ino == sd->s_ino;
> -}
> -
> /**
> * sysfs_addrm_start - prepare for sysfs_dirent add/remove
> * @acxt: pointer to sysfs_addrm_cxt to be used
> @@ -399,47 +393,20 @@ static int sysfs_ilookup_test(struct inode *inode, void *arg)
> *
> * This function is called when the caller is about to add or
> * remove sysfs_dirent under @parent_sd. This function acquires
> - * sysfs_mutex, grabs inode for @parent_sd if available and lock
> - * i_mutex of it. @acxt is used to keep and pass context to
> + * sysfs_mutex. @acxt is used to keep and pass context to
> * other addrm functions.
> *
> * LOCKING:
> * Kernel thread context (may sleep). sysfs_mutex is locked on
> - * return. i_mutex of parent inode is locked on return if
> - * available.
> + * return.
> */
> void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
> struct sysfs_dirent *parent_sd)
> {
> - struct inode *inode;
> -
> memset(acxt, 0, sizeof(*acxt));
> acxt->parent_sd = parent_sd;
>
> - /* Lookup parent inode. inode initialization is protected by
> - * sysfs_mutex, so inode existence can be determined by
> - * looking up inode while holding sysfs_mutex.
> - */
> mutex_lock(&sysfs_mutex);
> -
> - inode = ilookup5(sysfs_sb, parent_sd->s_ino, sysfs_ilookup_test,
> - parent_sd);
> - if (inode) {
> - WARN_ON(inode->i_state & I_NEW);
> -
> - /* parent inode available */
> - acxt->parent_inode = inode;
> -
> - /* sysfs_mutex is below i_mutex in lock hierarchy.
> - * First, trylock i_mutex. If fails, unlock
> - * sysfs_mutex and lock them in order.
> - */
> - if (!mutex_trylock(&inode->i_mutex)) {
> - mutex_unlock(&sysfs_mutex);
> - mutex_lock(&inode->i_mutex);
> - mutex_lock(&sysfs_mutex);
> - }
> - }
> }
>
> /**
> @@ -471,11 +438,6 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
>
> sd->s_parent = sysfs_get(acxt->parent_sd);
>
> - if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
> - inc_nlink(acxt->parent_inode);
> -
> - acxt->cnt++;
> -
> sysfs_link_sibling(sd);
>
> /* Update timestamps on the parent */
> @@ -579,40 +541,6 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
> sd->s_flags |= SYSFS_FLAG_REMOVED;
> sd->s_sibling = acxt->removed;
> acxt->removed = sd;
> -
> - if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
> - drop_nlink(acxt->parent_inode);
> -
> - acxt->cnt++;
> -}
> -
> -/**
> - * sysfs_dec_nlink - Decrement link count for the specified sysfs_dirent
> - * @sd: target sysfs_dirent
> - *
> - * Decrement nlink for @sd. @sd must have been unlinked from its
> - * parent on entry to this function such that it can't be looked
> - * up anymore.
> - */
> -static void sysfs_dec_nlink(struct sysfs_dirent *sd)
> -{
> - struct inode *inode;
> -
> - inode = ilookup(sysfs_sb, sd->s_ino);
> - if (!inode)
> - return;
> -
> - /* adjust nlink and update timestamp */
> - mutex_lock(&inode->i_mutex);
> -
> - inode->i_ctime = CURRENT_TIME;
> - drop_nlink(inode);
> - if (sysfs_type(sd) == SYSFS_DIR)
> - drop_nlink(inode);
> -
> - mutex_unlock(&inode->i_mutex);
> -
> - iput(inode);
> }
>
> /**
> @@ -621,25 +549,15 @@ static void sysfs_dec_nlink(struct sysfs_dirent *sd)
> *
> * Finish up sysfs_dirent add/remove. Resources acquired by
> * sysfs_addrm_start() are released and removed sysfs_dirents are
> - * cleaned up. Timestamps on the parent inode are updated.
> + * cleaned up.
> *
> * LOCKING:
> - * All mutexes acquired by sysfs_addrm_start() are released.
> + * sysfs_mutex is released.
> */
> void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
> {
> /* release resources acquired by sysfs_addrm_start() */
> mutex_unlock(&sysfs_mutex);
> - if (acxt->parent_inode) {
> - struct inode *inode = acxt->parent_inode;
> -
> - /* if added/removed, update timestamps on the parent */
> - if (acxt->cnt)
> - inode->i_ctime = inode->i_mtime = CURRENT_TIME;
> -
> - mutex_unlock(&inode->i_mutex);
> - iput(inode);
> - }
>
> /* kill removed sysfs_dirents */
> while (acxt->removed) {
> @@ -648,7 +566,6 @@ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
> acxt->removed = sd->s_sibling;
> sd->s_sibling = NULL;
>
> - sysfs_dec_nlink(sd);
> sysfs_deactivate(sd);
> unmap_bin_file(sd);
> sysfs_put(sd);
> diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
> index 12ccc07..90b3501 100644
> --- a/fs/sysfs/sysfs.h
> +++ b/fs/sysfs/sysfs.h
> @@ -89,9 +89,7 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
> */
> struct sysfs_addrm_cxt {
> struct sysfs_dirent *parent_sd;
> - struct inode *parent_inode;
> struct sysfs_dirent *removed;
> - int cnt;
> };
>
> /*
> --
> 1.6.5.2.143.g8cc62
>
> --
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