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Date: Thu, 30 Aug 2018 16:56:29 +0900 (JST)
From: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To: Souptick Joarder <jrdr.linux@...il.com>
Cc: willy@...radead.org, viro@...iv.linux.org.uk, tytso@....edu,
adilger.kernel@...ger.ca, darrick.wong@...cle.com, axboe@...nel.dk,
ebiggers@...gle.com, tglx@...utronix.de,
gregkh@...uxfoundation.org, kemi.wang@...el.com,
akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-nilfs@...r.kernel.org
Subject: Re: [PATCH] fs: Convert return type int to vm_fault_t
Hi,
On Wed, 29 Aug 2018 00:55:28 +0530, Souptick Joarder wrote:
> Return type for fault handlers in ext4 and nilfs are
> changed to use vm_fault_t.
>
> Return type of block_page_mkwrite() is changed from
> int to vm_fault_t. The function signature of
> block_page_mkwrite() is changed to add one new parameter
> int *err. This will provide a way for caller functions
> to get error number along with VM_FAULT return value and
> use it further.
>
> Return type of block_page_mkwrite_return() is also changed
> to use new vm_fault_t type.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> ---
> fs/buffer.c | 20 +++++++++++---------
> fs/ext4/ext4.h | 4 ++--
> fs/ext4/inode.c | 34 ++++++++++++++++++----------------
> fs/nilfs2/file.c | 16 ++++++++++------
> include/linux/buffer_head.h | 7 ++++---
> 5 files changed, 45 insertions(+), 36 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index ebf78ab..aacfc73 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2487,21 +2487,21 @@ int block_commit_write(struct page *page, unsigned from, unsigned to)
> * Direct callers of this function should protect against filesystem freezing
> * using sb_start_pagefault() - sb_end_pagefault() functions.
> */
> -int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> - get_block_t get_block)
> +vm_fault_t block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> + get_block_t get_block, int *err)
> {
> struct page *page = vmf->page;
> struct inode *inode = file_inode(vma->vm_file);
> unsigned long end;
> loff_t size;
> - int ret;
> + int err1;
>
> lock_page(page);
> size = i_size_read(inode);
> if ((page->mapping != inode->i_mapping) ||
> (page_offset(page) > size)) {
> /* We overload EFAULT to mean page got truncated */
> - ret = -EFAULT;
> + err1 = -EFAULT;
> goto out_unlock;
> }
>
> @@ -2511,18 +2511,20 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> else
> end = PAGE_SIZE;
>
> - ret = __block_write_begin(page, 0, end, get_block);
> - if (!ret)
> - ret = block_commit_write(page, 0, end);
> + err1 = __block_write_begin(page, 0, end, get_block);
> + if (!err1)
> + err1 = block_commit_write(page, 0, end);
>
> - if (unlikely(ret < 0))
> + if (unlikely(err1 < 0))
> goto out_unlock;
> + *err = err1;
> set_page_dirty(page);
> wait_for_stable_page(page);
> return 0;
> out_unlock:
> unlock_page(page);
> - return ret;
> + *err = err1;
> + return block_page_mkwrite_return(err1);
> }
> EXPORT_SYMBOL(block_page_mkwrite);
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 0f0edd1..8506b14 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2469,8 +2469,8 @@ int do_journal_get_write_access(handle_t *handle,
> extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
> extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
> loff_t lstart, loff_t lend);
> -extern int ext4_page_mkwrite(struct vm_fault *vmf);
> -extern int ext4_filemap_fault(struct vm_fault *vmf);
> +extern vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf);
> +extern vm_fault_t ext4_filemap_fault(struct vm_fault *vmf);
> extern qsize_t *ext4_get_reserved_space(struct inode *inode);
> extern int ext4_get_projid(struct inode *inode, kprojid_t *projid);
> extern void ext4_da_update_reserve_space(struct inode *inode,
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 82adee7..1062a8e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6151,39 +6151,40 @@ static int ext4_bh_unmapped(handle_t *handle, struct buffer_head *bh)
> return !buffer_mapped(bh);
> }
>
> -int ext4_page_mkwrite(struct vm_fault *vmf)
> +vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
> {
> struct vm_area_struct *vma = vmf->vma;
> struct page *page = vmf->page;
> loff_t size;
> unsigned long len;
> - int ret;
> + vm_fault_t ret;
> struct file *file = vma->vm_file;
> struct inode *inode = file_inode(file);
> struct address_space *mapping = inode->i_mapping;
> handle_t *handle;
> get_block_t *get_block;
> - int retries = 0;
> + int retries = 0, err;
>
> sb_start_pagefault(inode->i_sb);
> file_update_time(vma->vm_file);
>
> down_read(&EXT4_I(inode)->i_mmap_sem);
>
> - ret = ext4_convert_inline_data(inode);
> - if (ret)
> + err = ext4_convert_inline_data(inode);
> + if (err)
> goto out_ret;
>
> + err = 0;
> /* Delalloc case is easy... */
> if (test_opt(inode->i_sb, DELALLOC) &&
> !ext4_should_journal_data(inode) &&
> !ext4_nonda_switch(inode->i_sb)) {
> do {
> ret = block_page_mkwrite(vma, vmf,
> - ext4_da_get_block_prep);
> - } while (ret == -ENOSPC &&
> + ext4_da_get_block_prep, &err);
> + } while (err == -ENOSPC &&
> ext4_should_retry_alloc(inode->i_sb, &retries));
> - goto out_ret;
> + goto out;
> }
>
> lock_page(page);
> @@ -6226,36 +6227,37 @@ int ext4_page_mkwrite(struct vm_fault *vmf)
> ret = VM_FAULT_SIGBUS;
> goto out;
> }
> - ret = block_page_mkwrite(vma, vmf, get_block);
> + err = 0;
> + ret = block_page_mkwrite(vma, vmf, get_block, &err);
> if (!ret && ext4_should_journal_data(inode)) {
> if (ext4_walk_page_buffers(handle, page_buffers(page), 0,
> PAGE_SIZE, NULL, do_journal_get_write_access)) {
> unlock_page(page);
> - ret = VM_FAULT_SIGBUS;
> ext4_journal_stop(handle);
> goto out;
> }
> ext4_set_inode_state(inode, EXT4_STATE_JDATA);
> }
> ext4_journal_stop(handle);
> - if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
> + if (err == -ENOSPC &&
> + ext4_should_retry_alloc(inode->i_sb, &retries))
> goto retry_alloc;
> out_ret:
> - ret = block_page_mkwrite_return(ret);
> + ret = block_page_mkwrite_return(err);
> out:
> up_read(&EXT4_I(inode)->i_mmap_sem);
> sb_end_pagefault(inode->i_sb);
> return ret;
> }
>
> -int ext4_filemap_fault(struct vm_fault *vmf)
> +vm_fault_t ext4_filemap_fault(struct vm_fault *vmf)
> {
> struct inode *inode = file_inode(vmf->vma->vm_file);
> - int err;
> + vm_fault_t ret;
>
> down_read(&EXT4_I(inode)->i_mmap_sem);
> - err = filemap_fault(vmf);
> + ret = filemap_fault(vmf);
> up_read(&EXT4_I(inode)->i_mmap_sem);
>
> - return err;
> + return ret;
> }
> diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
> index 7da0fac..58d2a81 100644
> --- a/fs/nilfs2/file.c
> +++ b/fs/nilfs2/file.c
> @@ -57,7 +57,8 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
> struct page *page = vmf->page;
> struct inode *inode = file_inode(vma->vm_file);
> struct nilfs_transaction_info ti;
> - int ret = 0;
> + vm_fault_t ret = VM_FAULT_LOCKED;
> + int err = 0;
>
> if (unlikely(nilfs_near_disk_full(inode->i_sb->s_fs_info)))
> return VM_FAULT_SIGBUS; /* -ENOSPC */
> @@ -67,7 +68,7 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
> if (page->mapping != inode->i_mapping ||
> page_offset(page) >= i_size_read(inode) || !PageUptodate(page)) {
> unlock_page(page);
> - ret = -EFAULT; /* make the VM retry the fault */
> + ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
> goto out;
> }
>
> @@ -99,13 +100,16 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
> /*
> * fill hole blocks
> */
> - ret = nilfs_transaction_begin(inode->i_sb, &ti, 1);
> + err = nilfs_transaction_begin(inode->i_sb, &ti, 1);
> /* never returns -ENOMEM, but may return -ENOSPC */
> - if (unlikely(ret))
> + if (unlikely(err)) {
> + ret = block_page_mkwrite_return(err);
> goto out;
> + }
>
> + err = 0;
This initialization looks unnecessary. "err" is always zero here.
Regards,
Ryusuke Konishi
> file_update_time(vma->vm_file);
> - ret = block_page_mkwrite(vma, vmf, nilfs_get_block);
> + ret = block_page_mkwrite(vma, vmf, nilfs_get_block, &err);
> if (ret) {
> nilfs_transaction_abort(inode->i_sb);
> goto out;
> @@ -117,7 +121,7 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
> wait_for_stable_page(page);
> out:
> sb_end_pagefault(inode->i_sb);
> - return block_page_mkwrite_return(ret);
> + return ret;
> }
>
> static const struct vm_operations_struct nilfs_file_vm_ops = {
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index 96225a7..e212b13 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -14,6 +14,7 @@
> #include <linux/pagemap.h>
> #include <linux/wait.h>
> #include <linux/atomic.h>
> +#include <linux/mm_types.h>
>
> #ifdef CONFIG_BLOCK
>
> @@ -239,10 +240,10 @@ int cont_write_begin(struct file *, struct address_space *, loff_t,
> get_block_t *, loff_t *);
> int generic_cont_expand_simple(struct inode *inode, loff_t size);
> int block_commit_write(struct page *page, unsigned from, unsigned to);
> -int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> - get_block_t get_block);
> +vm_fault_t block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> + get_block_t get_block, int *err);
> /* Convert errno to return value from ->page_mkwrite() call */
> -static inline int block_page_mkwrite_return(int err)
> +static inline vm_fault_t block_page_mkwrite_return(int err)
> {
> if (err == 0)
> return VM_FAULT_LOCKED;
> --
> 1.9.1
>
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