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Message-ID: <87bofq39rs.fsf@tucsk.pomaz.szeredi.hu>
Date: Thu, 25 Oct 2012 16:29:27 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: Maxim Patlasov <mpatlasov@...allels.com>
Cc: fuse-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
devel@...nvz.org
Subject: Re: [PATCH 09/11] fuse: pass iov[] to fuse_get_user_pages()
Maxim Patlasov <mpatlasov@...allels.com> writes:
> The patch makes preliminary work for the next patch optimizing scatter-gather
> direct IO. The idea is to allow fuse_get_user_pages() to pack as many iov-s
> to each fuse request as possible. So, here we only rework all related
> call-paths to carry iov[] from fuse_direct_IO() to fuse_get_user_pages().
>
> Signed-off-by: Maxim Patlasov <mpatlasov@...allels.com>
> ---
> fs/fuse/file.c | 108 +++++++++++++++++++++++++++++---------------------------
> 1 files changed, 55 insertions(+), 53 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 8a1f833..db9efb5 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1056,11 +1056,15 @@ static inline void fuse_page_descs_length_init(struct fuse_req *req)
> req->page_descs[i].offset;
> }
>
> -static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
> +static int fuse_get_user_pages(struct fuse_req *req,
> + const struct iovec **iov_pp,
> + unsigned long *nr_segs_p,
> + size_t *iov_offset_p,
Aren't these arguments exactly what 'struct iov_iter' is supposed to
represent? Would be a nice cleanup, and in addition we'd get well
tested helper functions that iterate over the iovec.
> size_t *nbytesp, int write)
> {
> size_t nbytes = *nbytesp;
> - unsigned long user_addr = (unsigned long) buf;
> + size_t frag_size = min_t(size_t, nbytes, (*iov_pp)->iov_len - *iov_offset_p);
> + unsigned long user_addr = (unsigned long)(*iov_pp)->iov_base + *iov_offset_p;
> unsigned offset = user_addr & ~PAGE_MASK;
> int npages;
>
> @@ -1071,10 +1075,13 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
> else
> req->out.args[0].value = (void *) user_addr;
>
> + (*iov_pp)++;
> + (*nr_segs_p)--;
> + *nbytesp = frag_size;
> return 0;
> }
>
> - nbytes = min_t(size_t, nbytes, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
> + nbytes = min_t(size_t, frag_size, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
> npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
> npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
> npages = get_user_pages_fast(user_addr, npages, !write, req->pages);
> @@ -1092,17 +1099,26 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
>
> nbytes = (req->num_pages << PAGE_SHIFT) - req->page_descs[0].offset;
>
> - if (*nbytesp < nbytes)
> + if (frag_size < nbytes)
> req->page_descs[req->num_pages - 1].length -=
> - nbytes - *nbytesp;
> + nbytes - frag_size;
>
> - *nbytesp = min(*nbytesp, nbytes);
> + *nbytesp = min(frag_size, nbytes);
> +
> + if (*nbytesp < (*iov_pp)->iov_len - *iov_offset_p) {
> + *iov_offset_p += *nbytesp;
> + } else {
> + (*iov_pp)++;
> + (*nr_segs_p)--;
> + *iov_offset_p = 0;
> + }
>
> return 0;
> }
>
> -ssize_t fuse_direct_io(struct file *file, const char __user *buf,
> - size_t count, loff_t *ppos, int write)
> +static ssize_t __fuse_direct_io(struct file *file, const struct iovec *iov,
> + unsigned long nr_segs, size_t count,
> + loff_t *ppos, int write)
> {
> struct fuse_file *ff = file->private_data;
> struct fuse_conn *fc = ff->fc;
> @@ -1110,6 +1126,7 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
> loff_t pos = *ppos;
> ssize_t res = 0;
> struct fuse_req *req;
> + size_t iov_offset = 0;
>
> req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
> if (IS_ERR(req))
> @@ -1119,7 +1136,8 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
> size_t nres;
> fl_owner_t owner = current->files;
> size_t nbytes = min(count, nmax);
> - int err = fuse_get_user_pages(req, buf, &nbytes, write);
> + int err = fuse_get_user_pages(req, &iov, &nr_segs, &iov_offset,
> + &nbytes, write);
> if (err) {
> res = err;
> break;
> @@ -1142,7 +1160,6 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
> count -= nres;
> res += nres;
> pos += nres;
> - buf += nres;
> if (nres != nbytes)
> break;
> if (count) {
> @@ -1159,10 +1176,17 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
>
> return res;
> }
> +
> +ssize_t fuse_direct_io(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos, int write)
> +{
> + struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
> + return __fuse_direct_io(file, &iov, 1, count, ppos, write);
> +}
> EXPORT_SYMBOL_GPL(fuse_direct_io);
>
> -static ssize_t fuse_direct_read(struct file *file, char __user *buf,
> - size_t count, loff_t *ppos)
> +static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov,
> + unsigned long nr_segs, loff_t *ppos)
> {
> ssize_t res;
> struct inode *inode = file->f_path.dentry->d_inode;
> @@ -1170,22 +1194,31 @@ static ssize_t fuse_direct_read(struct file *file, char __user *buf,
> if (is_bad_inode(inode))
> return -EIO;
>
> - res = fuse_direct_io(file, buf, count, ppos, 0);
> + res = __fuse_direct_io(file, iov, nr_segs, iov_length(iov, nr_segs),
> + ppos, 0);
>
> fuse_invalidate_attr(inode);
>
> return res;
> }
>
> -static ssize_t __fuse_direct_write(struct file *file, const char __user *buf,
> - size_t count, loff_t *ppos)
> +static ssize_t fuse_direct_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
> + return __fuse_direct_read(file, &iov, 1, ppos);
> +}
> +
> +static ssize_t __fuse_direct_write(struct file *file, const struct iovec *iov,
> + unsigned long nr_segs, loff_t *ppos)
> {
> struct inode *inode = file->f_path.dentry->d_inode;
> + size_t count = iov_length(iov, nr_segs);
> ssize_t res;
>
> res = generic_write_checks(file, ppos, &count, 0);
> if (!res) {
> - res = fuse_direct_io(file, buf, count, ppos, 1);
> + res = __fuse_direct_io(file, iov, nr_segs, count, ppos, 1);
> if (res > 0)
> fuse_write_update_size(inode, *ppos);
> }
> @@ -1198,6 +1231,7 @@ static ssize_t __fuse_direct_write(struct file *file, const char __user *buf,
> static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
> size_t count, loff_t *ppos)
> {
> + struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
> struct inode *inode = file->f_path.dentry->d_inode;
> ssize_t res;
>
> @@ -1206,7 +1240,7 @@ static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
>
> /* Don't allow parallel writes to the same file */
> mutex_lock(&inode->i_mutex);
> - res = __fuse_direct_write(file, buf, count, ppos);
> + res = __fuse_direct_write(file, &iov, 1, ppos);
> mutex_unlock(&inode->i_mutex);
>
> return res;
> @@ -2166,41 +2200,6 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc,
> return 0;
> }
>
> -static ssize_t fuse_loop_dio(struct file *filp, const struct iovec *iov,
> - unsigned long nr_segs, loff_t *ppos, int rw)
> -{
> - const struct iovec *vector = iov;
> - ssize_t ret = 0;
> -
> - while (nr_segs > 0) {
> - void __user *base;
> - size_t len;
> - ssize_t nr;
> -
> - base = vector->iov_base;
> - len = vector->iov_len;
> - vector++;
> - nr_segs--;
> -
> - if (rw == WRITE)
> - nr = __fuse_direct_write(filp, base, len, ppos);
> - else
> - nr = fuse_direct_read(filp, base, len, ppos);
> -
> - if (nr < 0) {
> - if (!ret)
> - ret = nr;
> - break;
> - }
> - ret += nr;
> - if (nr != len)
> - break;
> - }
> -
> - return ret;
> -}
> -
> -
> static ssize_t
> fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
> loff_t offset, unsigned long nr_segs)
> @@ -2212,7 +2211,10 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
> file = iocb->ki_filp;
> pos = offset;
>
> - ret = fuse_loop_dio(file, iov, nr_segs, &pos, rw);
> + if (rw == WRITE)
> + ret = __fuse_direct_write(file, iov, nr_segs, &pos);
> + else
> + ret = __fuse_direct_read(file, iov, nr_segs, &pos);
>
> return ret;
> }
--
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