Re: [PATCH 1 of 2] Implement generic block_page_mkwrite() functionality
From: David Chinner <hidden>
Date: 2007-02-07 12:55:43
Also in:
linux-fsdevel, linux-xfs
Mental Note: must remember to refresh patch after fixing compile errors. New patch attached. - On Christoph's suggestion, take the guts of the proposed xfs_vm_page_mkwrite function and implement it as a generic core function as it used no specific XFS code at all. This allows any filesystem to easily hook the ->page_mkwrite() VM callout to allow them to set up pages dirtied by mmap writes correctly for later writeout. Signed-Off-By: Dave Chinner <redacted> --- fs/buffer.c | 30 ++++++++++++++++++++++++++++++ include/linux/buffer_head.h | 2 ++ 2 files changed, 32 insertions(+) Index: 2.6.x-xfs-new/fs/buffer.c ===================================================================
--- 2.6.x-xfs-new.orig/fs/buffer.c 2007-02-07 23:00:05.000000000 +1100
+++ 2.6.x-xfs-new/fs/buffer.c 2007-02-07 23:09:47.642356116 +1100@@ -2194,6 +2194,36 @@ int generic_commit_write(struct file *fi return 0; } +/* + * block_page_mkwrite() is not allowed to change the file size as + * it gets called from a page fault handler when a page is first + * dirtied. Hence we must be careful to check for EOF conditions + * here. We set the page up correctly for a written page which means + * we get ENOSPC checking when writing into holes and correct + * delalloc and unwritten extent mapping on filesystems that support + * these features. + */ +int +block_page_mkwrite(struct vm_area_struct *vma, struct page *page, + get_block_t get_block) +{ + struct inode *inode = vma->vm_file->f_path.dentry->d_inode; + unsigned long end; + int ret = 0; + + if (((page->index + 1) << PAGE_CACHE_SHIFT) > i_size_read(inode)) + end = i_size_read(inode) & ~PAGE_CACHE_MASK; + else + end = PAGE_CACHE_SIZE; + + lock_page(page); + ret = block_prepare_write(page, 0, end, get_block); + if (!ret) + ret = block_commit_write(page, 0, end); + unlock_page(page); + + return ret; +} /* * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
Index: 2.6.x-xfs-new/include/linux/buffer_head.h ===================================================================
--- 2.6.x-xfs-new.orig/include/linux/buffer_head.h 2007-02-07 23:00:02.000000000 +1100
+++ 2.6.x-xfs-new/include/linux/buffer_head.h 2007-02-07 23:19:25.110816993 +1100@@ -206,6 +206,8 @@ int cont_prepare_write(struct page*, uns int generic_cont_expand(struct inode *inode, loff_t size); 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 page *page, + get_block_t get_block); void block_sync_page(struct page *); sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); int generic_commit_write(struct file *, struct page *, unsigned, unsigned); --
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