From 7ffdea7ea36cd1efebab65d1b221f05deaab00cd Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 26 Jan 2013 00:11:36 +0000 Subject: locking in fs/9p ->readdir() ... is really excessive. First of all, ->readdir() is serialized by file->f_path.dentry->d_inode->i_mutex; playing with file->f_path.dentry->d_lock is not buying you anything. Moreover, rdir->mutex is pointless for exactly the same reason - you'll never see contention on it. While we are at it, there's no point in having rdir->buf a pointer - you have it point just past the end of rdir, so it might as well be a flex array (and no, it's not a gccism). Absolutely untested patch follows: Signed-off-by: Al Viro Signed-off-by: Eric Van Hensbergen --- fs/9p/vfs_dir.c | 92 +++++++++++++++------------------------------------------ 1 file changed, 23 insertions(+), 69 deletions(-) (limited to 'fs/9p') diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c index ff911e779651..be1e34adc3c6 100644 --- a/fs/9p/vfs_dir.c +++ b/fs/9p/vfs_dir.c @@ -52,10 +52,9 @@ */ struct p9_rdir { - struct mutex mutex; int head; int tail; - uint8_t *buf; + uint8_t buf[]; }; /** @@ -93,33 +92,12 @@ static void p9stat_init(struct p9_wstat *stbuf) * */ -static int v9fs_alloc_rdir_buf(struct file *filp, int buflen) +static struct p9_rdir *v9fs_alloc_rdir_buf(struct file *filp, int buflen) { - struct p9_rdir *rdir; - struct p9_fid *fid; - int err = 0; - - fid = filp->private_data; - if (!fid->rdir) { - rdir = kmalloc(sizeof(struct p9_rdir) + buflen, GFP_KERNEL); - - if (rdir == NULL) { - err = -ENOMEM; - goto exit; - } - spin_lock(&filp->f_dentry->d_lock); - if (!fid->rdir) { - rdir->buf = (uint8_t *)rdir + sizeof(struct p9_rdir); - mutex_init(&rdir->mutex); - rdir->head = rdir->tail = 0; - fid->rdir = (void *) rdir; - rdir = NULL; - } - spin_unlock(&filp->f_dentry->d_lock); - kfree(rdir); - } -exit: - return err; + struct p9_fid *fid = filp->private_data; + if (!fid->rdir) + fid->rdir = kzalloc(sizeof(struct p9_rdir) + buflen, GFP_KERNEL); + return fid->rdir; } /** @@ -145,20 +123,16 @@ static int v9fs_dir_readdir(struct file *filp, void *dirent, filldir_t filldir) buflen = fid->clnt->msize - P9_IOHDRSZ; - err = v9fs_alloc_rdir_buf(filp, buflen); - if (err) - goto exit; - rdir = (struct p9_rdir *) fid->rdir; + rdir = v9fs_alloc_rdir_buf(filp, buflen); + if (!rdir) + return -ENOMEM; - err = mutex_lock_interruptible(&rdir->mutex); - if (err) - return err; - while (err == 0) { + while (1) { if (rdir->tail == rdir->head) { err = v9fs_file_readn(filp, rdir->buf, NULL, buflen, filp->f_pos); if (err <= 0) - goto unlock_and_exit; + return err; rdir->head = 0; rdir->tail = err; @@ -169,9 +143,8 @@ static int v9fs_dir_readdir(struct file *filp, void *dirent, filldir_t filldir) rdir->tail - rdir->head, &st); if (err) { p9_debug(P9_DEBUG_VFS, "returned %d\n", err); - err = -EIO; p9stat_free(&st); - goto unlock_and_exit; + return -EIO; } reclen = st.size+2; @@ -180,19 +153,13 @@ static int v9fs_dir_readdir(struct file *filp, void *dirent, filldir_t filldir) p9stat_free(&st); - if (over) { - err = 0; - goto unlock_and_exit; - } + if (over) + return 0; + rdir->head += reclen; filp->f_pos += reclen; } } - -unlock_and_exit: - mutex_unlock(&rdir->mutex); -exit: - return err; } /** @@ -218,21 +185,16 @@ static int v9fs_dir_readdir_dotl(struct file *filp, void *dirent, buflen = fid->clnt->msize - P9_READDIRHDRSZ; - err = v9fs_alloc_rdir_buf(filp, buflen); - if (err) - goto exit; - rdir = (struct p9_rdir *) fid->rdir; + rdir = v9fs_alloc_rdir_buf(filp, buflen); + if (!rdir) + return -ENOMEM; - err = mutex_lock_interruptible(&rdir->mutex); - if (err) - return err; - - while (err == 0) { + while (1) { if (rdir->tail == rdir->head) { err = p9_client_readdir(fid, rdir->buf, buflen, filp->f_pos); if (err <= 0) - goto unlock_and_exit; + return err; rdir->head = 0; rdir->tail = err; @@ -245,8 +207,7 @@ static int v9fs_dir_readdir_dotl(struct file *filp, void *dirent, &curdirent); if (err < 0) { p9_debug(P9_DEBUG_VFS, "returned %d\n", err); - err = -EIO; - goto unlock_and_exit; + return -EIO; } /* d_off in dirent structure tracks the offset into @@ -261,20 +222,13 @@ static int v9fs_dir_readdir_dotl(struct file *filp, void *dirent, curdirent.d_type); oldoffset = curdirent.d_off; - if (over) { - err = 0; - goto unlock_and_exit; - } + if (over) + return 0; filp->f_pos = curdirent.d_off; rdir->head += err; } } - -unlock_and_exit: - mutex_unlock(&rdir->mutex); -exit: - return err; } -- cgit v1.2.3