On Wed 15-01-14 20:24:24, Matthew Wilcox wrote:
> Instead of separate read and write methods, use the generic AIO
> infrastructure. In addition to giving us support for AIO, this adds
> the locking between read() and truncate() that was missing.
>
> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
> ---
> fs/Makefile | 1 +
> fs/ext2/file.c | 6 +-
> fs/ext2/inode.c | 7 +-
> fs/xip.c | 156 +++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 18 ++++-
> mm/filemap.c | 6 +-
> mm/filemap_xip.c | 234 -----------------------------------------------------
> 7 files changed, 183 insertions(+), 245 deletions(-)
> create mode 100644 fs/xip.c
>
...
> +static ssize_t xip_io(int rw, struct inode *inode, const struct iovec *iov,
> + loff_t start, loff_t end, unsigned nr_segs,
> + get_block_t get_block, struct buffer_head *bh)
> +{
> + ssize_t retval = 0;
> + unsigned seg = 0;
> + unsigned len;
> + unsigned copied = 0;
> + loff_t offset = start;
> + loff_t max = start;
> + void *addr;
> + bool hole = false;
> +
> + while (offset < end) {
> + void __user *buf = iov[seg].iov_base + copied;
> +
> + if (max == offset) {
> + sector_t block = offset >> inode->i_blkbits;
> + long size;
> + memset(bh, 0, sizeof(*bh));
> + bh->b_size = ALIGN(end - offset, PAGE_SIZE);
> + retval = get_block(inode, block, bh, rw == WRITE);
> + if (retval)
> + break;
> + if (buffer_mapped(bh)) {
> + retval = xip_get_addr(inode, bh, &addr);
> + if (retval < 0)
> + break;
> + addr += offset - (block << inode->i_blkbits);
> + hole = false;
> + size = retval;
I think you are missing here zeroing out partial pages at the head and
the tail of the mapped extent when buffer_new(bh). Dave Chinner found this
in his testing as well I think.
Honza
> + } else {
> + if (rw == WRITE) {
> + retval = -EIO;
> + break;
> + }
> + addr = NULL;
> + hole = true;
> + size = bh->b_size;
> + }
> + max = offset + size;
> + }
> +
> + len = min_t(unsigned, iov[seg].iov_len - copied, max - offset);
> +
> + if (rw == WRITE)
> + len -= __copy_from_user_nocache(addr, buf, len);
> + else if (!hole)
> + len -= __copy_to_user(buf, addr, len);
> + else
> + len -= __clear_user(buf, len);
> +
> + if (!len)
> + break;
> +
> + offset += len;
> + copied += len;
> + if (copied == iov[seg].iov_len) {
> + seg++;
> + copied = 0;
> + }
> + }
> +
> + return (offset == start) ? retval : offset - start;
> +}
> +
> +/**
> + * xip_do_io - Perform I/O to an XIP file
> + * @rw: READ to read or WRITE to write
> + * @iocb: The control block for this I/O
> + * @inode: The file which the I/O is directed at
> + * @iov: The user addresses to do I/O from or to
> + * @offset: The file offset where the I/O starts
> + * @nr_segs: The length of the iov array
> + * @get_block: The filesystem method used to translate file offsets to blocks
> + * @end_io: A filesystem callback for I/O completion
> + * @flags: See below
> + *
> + * This function uses the same locking scheme as do_blockdev_direct_IO:
> + * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
> + * caller for writes. For reads, we take and release the i_mutex ourselves.
> + * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
> + * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
> + * is in progress.
> + */
> +ssize_t xip_do_io(int rw, struct kiocb *iocb, struct inode *inode,
> + const struct iovec *iov, loff_t offset, unsigned nr_segs,
> + get_block_t get_block, dio_iodone_t end_io, int flags)
> +{
> + struct buffer_head bh;
> + unsigned seg;
> + ssize_t retval = -EINVAL;
> + loff_t end = offset;
> +
> + for (seg = 0; seg < nr_segs; seg++)
> + end += iov[seg].iov_len;
> +
> + if ((flags & DIO_LOCKING) && (rw == READ)) {
> + struct address_space *mapping = inode->i_mapping;
> + mutex_lock(&inode->i_mutex);
> + retval = filemap_write_and_wait_range(mapping, offset, end - 1);
> + if (retval) {
> + mutex_unlock(&inode->i_mutex);
> + goto out;
> + }
> + }
> +
> + /* Protects against truncate */
> + atomic_inc(&inode->i_dio_count);
> +
> + retval = xip_io(rw, inode, iov, offset, end, nr_segs, get_block, &bh);
> +
> + if ((flags & DIO_LOCKING) && (rw == READ))
> + mutex_unlock(&inode->i_mutex);
> +
> + inode_dio_done(inode);
> +
> + if ((retval > 0) && end_io)
> + end_io(iocb, offset, retval, bh.b_private);
> + out:
> + return retval;
> +}
> +EXPORT_SYMBOL_GPL(xip_do_io);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 80cfb42..7cc5bf7 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2509,17 +2509,22 @@ extern int generic_file_open(struct inode * inode, struct file * filp);
> extern int nonseekable_open(struct inode * inode, struct file * filp);
>
> #ifdef CONFIG_FS_XIP
> -extern ssize_t xip_file_read(struct file *filp, char __user *buf, size_t len,
> - loff_t *ppos);
> extern int xip_file_mmap(struct file * file, struct vm_area_struct * vma);
> -extern ssize_t xip_file_write(struct file *filp, const char __user *buf,
> - size_t len, loff_t *ppos);
> extern int xip_truncate_page(struct address_space *mapping, loff_t from);
> +ssize_t xip_do_io(int rw, struct kiocb *, struct inode *, const struct iovec *,
> + loff_t, unsigned segs, get_block_t, dio_iodone_t, int flags);
> #else
> static inline int xip_truncate_page(struct address_space *mapping, loff_t from)
> {
> return 0;
> }
> +
> +static inline ssize_t xip_do_io(int rw, struct kiocb *iocb, struct inode *inode,
> + const struct iovec *iov, loff_t offset, unsigned nr_segs,
> + get_block_t get_block, dio_iodone_t end_io, int flags)
> +{
> + return -ENOTTY;
> +}
> #endif
>
> #ifdef CONFIG_BLOCK
> @@ -2669,6 +2674,11 @@ extern int generic_show_options(struct seq_file *m, struct dentry *root);
> extern void save_mount_options(struct super_block *sb, char *options);
> extern void replace_mount_options(struct super_block *sb, char *options);
>
> +static inline bool io_is_direct(struct file *filp)
> +{
> + return (filp->f_flags & O_DIRECT) || IS_XIP(file_inode(filp));
> +}
> +
> static inline ino_t parent_ino(struct dentry *dentry)
> {
> ino_t res;
> diff --git a/mm/filemap.c b/mm/filemap.c
> index b7749a9..61a31f0 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1417,8 +1417,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
> if (retval)
> return retval;
>
> - /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
> - if (filp->f_flags & O_DIRECT) {
> + if (io_is_direct(filp)) {
> loff_t size;
> struct address_space *mapping;
> struct inode *inode;
> @@ -2470,8 +2469,7 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> if (err)
> goto out;
>
> - /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
> - if (unlikely(file->f_flags & O_DIRECT)) {
> + if (io_is_direct(file)) {
> loff_t endbyte;
> ssize_t written_buffered;
>
> diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
> index c8d23e9..f7c37a1 100644
> --- a/mm/filemap_xip.c
> +++ b/mm/filemap_xip.c
> @@ -42,119 +42,6 @@ static struct page *xip_sparse_page(void)
> }
>
> /*
> - * This is a file read routine for execute in place files, and uses
> - * the mapping->a_ops->get_xip_mem() function for the actual low-level
> - * stuff.
> - *
> - * Note the struct file* is not used at all. It may be NULL.
> - */
> -static ssize_t
> -do_xip_mapping_read(struct address_space *mapping,
> - struct file_ra_state *_ra,
> - struct file *filp,
> - char __user *buf,
> - size_t len,
> - loff_t *ppos)
> -{
> - struct inode *inode = mapping->host;
> - pgoff_t index, end_index;
> - unsigned long offset;
> - loff_t isize, pos;
> - size_t copied = 0, error = 0;
> -
> - BUG_ON(!mapping->a_ops->get_xip_mem);
> -
> - pos = *ppos;
> - index = pos >> PAGE_CACHE_SHIFT;
> - offset = pos & ~PAGE_CACHE_MASK;
> -
> - isize = i_size_read(inode);
> - if (!isize)
> - goto out;
> -
> - end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
> - do {
> - unsigned long nr, left;
> - void *xip_mem;
> - unsigned long xip_pfn;
> - int zero = 0;
> -
> - /* nr is the maximum number of bytes to copy from this page */
> - nr = PAGE_CACHE_SIZE;
> - if (index >= end_index) {
> - if (index > end_index)
> - goto out;
> - nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
> - if (nr <= offset) {
> - goto out;
> - }
> - }
> - nr = nr - offset;
> - if (nr > len - copied)
> - nr = len - copied;
> -
> - error = mapping->a_ops->get_xip_mem(mapping, index, 0,
> - &xip_mem, &xip_pfn);
> - if (unlikely(error)) {
> - if (error == -ENODATA) {
> - /* sparse */
> - zero = 1;
> - } else
> - goto out;
> - }
> -
> - /* If users can be writing to this page using arbitrary
> - * virtual addresses, take care about potential aliasing
> - * before reading the page on the kernel side.
> - */
> - if (mapping_writably_mapped(mapping))
> - /* address based flush */ ;
> -
> - /*
> - * Ok, we have the mem, so now we can copy it to user space...
> - *
> - * The actor routine returns how many bytes were actually used..
> - * NOTE! This may not be the same as how much of a user buffer
> - * we filled up (we may be padding etc), so we can only update
> - * "pos" here (the actor routine has to update the user buffer
> - * pointers and the remaining count).
> - */
> - if (!zero)
> - left = __copy_to_user(buf+copied, xip_mem+offset, nr);
> - else
> - left = __clear_user(buf + copied, nr);
> -
> - if (left) {
> - error = -EFAULT;
> - goto out;
> - }
> -
> - copied += (nr - left);
> - offset += (nr - left);
> - index += offset >> PAGE_CACHE_SHIFT;
> - offset &= ~PAGE_CACHE_MASK;
> - } while (copied < len);
> -
> -out:
> - *ppos = pos + copied;
> - if (filp)
> - file_accessed(filp);
> -
> - return (copied ? copied : error);
> -}
> -
> -ssize_t
> -xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
> -{
> - if (!access_ok(VERIFY_WRITE, buf, len))
> - return -EFAULT;
> -
> - return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
> - buf, len, ppos);
> -}
> -EXPORT_SYMBOL_GPL(xip_file_read);
> -
> -/*
> * __xip_unmap is invoked from xip_unmap and
> * xip_write
> *
> @@ -340,127 +227,6 @@ int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
> }
> EXPORT_SYMBOL_GPL(xip_file_mmap);
>
> -static ssize_t
> -__xip_file_write(struct file *filp, const char __user *buf,
> - size_t count, loff_t pos, loff_t *ppos)
> -{
> - struct address_space * mapping = filp->f_mapping;
> - const struct address_space_operations *a_ops = mapping->a_ops;
> - struct inode *inode = mapping->host;
> - long status = 0;
> - size_t bytes;
> - ssize_t written = 0;
> -
> - BUG_ON(!mapping->a_ops->get_xip_mem);
> -
> - do {
> - unsigned long index;
> - unsigned long offset;
> - size_t copied;
> - void *xip_mem;
> - unsigned long xip_pfn;
> -
> - offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
> - index = pos >> PAGE_CACHE_SHIFT;
> - bytes = PAGE_CACHE_SIZE - offset;
> - if (bytes > count)
> - bytes = count;
> -
> - status = a_ops->get_xip_mem(mapping, index, 0,
> - &xip_mem, &xip_pfn);
> - if (status == -ENODATA) {
> - /* we allocate a new page unmap it */
> - mutex_lock(&xip_sparse_mutex);
> - status = a_ops->get_xip_mem(mapping, index, 1,
> - &xip_mem, &xip_pfn);
> - mutex_unlock(&xip_sparse_mutex);
> - if (!status)
> - /* unmap page at pgoff from all other vmas */
> - __xip_unmap(mapping, index);
> - }
> -
> - if (status)
> - break;
> -
> - copied = bytes -
> - __copy_from_user_nocache(xip_mem + offset, buf, bytes);
> -
> - if (likely(copied > 0)) {
> - status = copied;
> -
> - if (status >= 0) {
> - written += status;
> - count -= status;
> - pos += status;
> - buf += status;
> - }
> - }
> - if (unlikely(copied != bytes))
> - if (status >= 0)
> - status = -EFAULT;
> - if (status < 0)
> - break;
> - } while (count);
> - *ppos = pos;
> - /*
> - * No need to use i_size_read() here, the i_size
> - * cannot change under us because we hold i_mutex.
> - */
> - if (pos > inode->i_size) {
> - i_size_write(inode, pos);
> - mark_inode_dirty(inode);
> - }
> -
> - return written ? written : status;
> -}
> -
> -ssize_t
> -xip_file_write(struct file *filp, const char __user *buf, size_t len,
> - loff_t *ppos)
> -{
> - struct address_space *mapping = filp->f_mapping;
> - struct inode *inode = mapping->host;
> - size_t count;
> - loff_t pos;
> - ssize_t ret;
> -
> - mutex_lock(&inode->i_mutex);
> -
> - if (!access_ok(VERIFY_READ, buf, len)) {
> - ret=-EFAULT;
> - goto out_up;
> - }
> -
> - pos = *ppos;
> - count = len;
> -
> - /* We can write back this queue in page reclaim */
> - current->backing_dev_info = mapping->backing_dev_info;
> -
> - ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
> - if (ret)
> - goto out_backing;
> - if (count == 0)
> - goto out_backing;
> -
> - ret = file_remove_suid(filp);
> - if (ret)
> - goto out_backing;
> -
> - ret = file_update_time(filp);
> - if (ret)
> - goto out_backing;
> -
> - ret = __xip_file_write (filp, buf, count, pos, ppos);
> -
> - out_backing:
> - current->backing_dev_info = NULL;
> - out_up:
> - mutex_unlock(&inode->i_mutex);
> - return ret;
> -}
> -EXPORT_SYMBOL_GPL(xip_file_write);
> -
> /*
> * truncate a page used for execute in place
> * functionality is analog to block_truncate_page but does use get_xip_mem
> --
> 1.8.5.2
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>