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fs: introduce write_begin, write_end, and perform_write aops

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These are intended to replace prepare_write and commit_write with more
flexible alternatives that are also able to avoid the buffered write
deadlock problems efficiently (which prepare_write is unable to do).

[mark.fasheh@oracle.com: API design contributions, code review and fixes]
[akpm@linux-foundation.org: various fixes]
[dmonakhov@sw.ru: new aop block_write_begin fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-10-16 01:25:01 -07:00 • committed by Linus Torvalds
parent 637aff46f9
commit afddba49d1
11 changed files with 575 additions and 206 deletions
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44
fs/libfs.c
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@ -351,6 +351,26 @@ int simple_prepare_write(struct file *file, struct page *page,
return 0;
}
int simple_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
struct page *page;
pgoff_t index;
unsigned from;
index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
page = __grab_cache_page(mapping, index);
if (!page)
return -ENOMEM;
*pagep = page;
return simple_prepare_write(file, page, from, from+len);
}
int simple_commit_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
@ -369,6 +389,28 @@ int simple_commit_write(struct file *file, struct page *page,
return 0;
}
int simple_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
unsigned from = pos & (PAGE_CACHE_SIZE - 1);
/* zero the stale part of the page if we did a short copy */
if (copied < len) {
void *kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr + from + copied, 0, len - copied);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
}
simple_commit_write(file, page, from, from+copied);
unlock_page(page);
page_cache_release(page);
return copied;
}
/*
* the inodes created here are not hashed. If you use iunique to generate
* unique inode values later for this filesystem, then you must take care
@ -642,6 +684,8 @@ EXPORT_SYMBOL(dcache_dir_open);
EXPORT_SYMBOL(dcache_readdir);
EXPORT_SYMBOL(generic_read_dir);
EXPORT_SYMBOL(get_sb_pseudo);
EXPORT_SYMBOL(simple_write_begin);
EXPORT_SYMBOL(simple_write_end);
EXPORT_SYMBOL(simple_commit_write);
EXPORT_SYMBOL(simple_dir_inode_operations);
EXPORT_SYMBOL(simple_dir_operations);