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fs: remove prepare_write/commit_write

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Nothing uses prepare_write or commit_write. Remove them from the tree
completely.

[akpm@linux-foundation.org: schedule simple_prepare_write() for unexporting]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
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 2008-10-29 14:00:55 -07:00 committed by Linus Torvalds
parent 9b913735e5
commit 4e02ed4b4a
9 changed files with 23 additions and 293 deletions
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12
Documentation/filesystems/Locking
View File

@ -161,8 +161,12 @@ prototypes:
int (*set_page_dirty)(struct page *page);
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
int (*write_begin)(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata);
int (*write_end)(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata);
sector_t (*bmap)(struct address_space *, sector_t);
int (*invalidatepage) (struct page *, unsigned long);
int (*releasepage) (struct page *, int);
@ -180,8 +184,6 @@ sync_page: no maybe
writepages: no
set_page_dirty no no
readpages: no
prepare_write: no yes yes
commit_write: no yes yes
write_begin: no locks the page yes
write_end: no yes, unlocks yes
perform_write: no n/a yes
@ -191,7 +193,7 @@ releasepage: no yes
direct_IO: no
launder_page: no yes
->prepare_write(), ->commit_write(), ->sync_page() and ->readpage()
->write_begin(), ->write_end(), ->sync_page() and ->readpage()
may be called from the request handler (/dev/loop).
->readpage() unlocks the page, either synchronously or via I/O

39
Documentation/filesystems/vfs.txt
View File

@ -492,7 +492,7 @@ written-back to storage typically in whole pages, however the
address_space has finer control of write sizes.
The read process essentially only requires 'readpage'. The write
process is more complicated and uses prepare_write/commit_write or
process is more complicated and uses write_begin/write_end or
set_page_dirty to write data into the address_space, and writepage,
sync_page, and writepages to writeback data to storage.
@ -521,8 +521,6 @@ struct address_space_operations {
int (*set_page_dirty)(struct page *page);
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
int (*write_begin)(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata);
@ -598,37 +596,7 @@ struct address_space_operations {
readpages is only used for read-ahead, so read errors are
ignored. If anything goes wrong, feel free to give up.
prepare_write: called by the generic write path in VM to set up a write
request for a page. This indicates to the address space that
the given range of bytes is about to be written. The
address_space should check that the write will be able to
complete, by allocating space if necessary and doing any other
internal housekeeping. If the write will update parts of
any basic-blocks on storage, then those blocks should be
pre-read (if they haven't been read already) so that the
updated blocks can be written out properly.
The page will be locked.
Note: the page _must not_ be marked uptodate in this function
(or anywhere else) unless it actually is uptodate right now. As
soon as a page is marked uptodate, it is possible for a concurrent
read(2) to copy it to userspace.
commit_write: If prepare_write succeeds, new data will be copied
into the page and then commit_write will be called. It will
typically update the size of the file (if appropriate) and
mark the inode as dirty, and do any other related housekeeping
operations. It should avoid returning an error if possible -
errors should have been handled by prepare_write.
write_begin: This is intended as a replacement for prepare_write. The
key differences being that:
- it returns a locked page (in *pagep) rather than being
given a pre locked page;
- it must be able to cope with short writes (where the
length passed to write_begin is greater than the number
of bytes copied into the page).
write_begin:
Called by the generic buffered write code to ask the filesystem to
prepare to write len bytes at the given offset in the file. The
address_space should check that the write will be able to complete,
@ -640,6 +608,9 @@ struct address_space_operations {
The filesystem must return the locked pagecache page for the specified
offset, in *pagep, for the caller to write into.
It must be able to cope with short writes (where the length passed to
write_begin is greater than the number of bytes copied into the page).
flags is a field for AOP_FLAG_xxx flags, described in
include/linux/fs.h.

5
drivers/block/loop.c
View File

@ -40,8 +40,7 @@
* Heinz Mauelshagen <mge@sistina.com>, Feb 2002
*
* Support for falling back on the write file operation when the address space
* operations prepare_write and/or commit_write are not available on the
* backing filesystem.
* operations write_begin is not available on the backing filesystem.
* Anton Altaparmakov, 16 Feb 2005
*
* Still To Fix:
@ -765,7 +764,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
*/
if (!file->f_op->splice_read)
goto out_putf;
if (aops->prepare_write || aops->write_begin)
if (aops->write_begin)
lo_flags |= LO_FLAGS_USE_AOPS;
if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
lo_flags |= LO_FLAGS_READ_ONLY;

2
fs/fat/inode.c
View File

@ -175,7 +175,7 @@ static ssize_t fat_direct_IO(int rw, struct kiocb *iocb,
if (rw == WRITE) {
/*
* FIXME: blockdev_direct_IO() doesn't use ->prepare_write(),
* FIXME: blockdev_direct_IO() doesn't use ->write_begin(),
* so we need to update the ->mmu_private to block boundary.
*
* But we must fill the remaining area or hole by nul for

2
fs/libfs.c
View File

@ -814,7 +814,7 @@ EXPORT_SYMBOL(simple_getattr);
EXPORT_SYMBOL(simple_link);
EXPORT_SYMBOL(simple_lookup);
EXPORT_SYMBOL(simple_pin_fs);
EXPORT_SYMBOL(simple_prepare_write);
EXPORT_UNUSED_SYMBOL(simple_prepare_write);
EXPORT_SYMBOL(simple_readpage);
EXPORT_SYMBOL(simple_release_fs);
EXPORT_SYMBOL(simple_rename);

3
fs/ocfs2/file.c
View File

@ -679,8 +679,7 @@ leave:
/* Some parts of this taken from generic_cont_expand, which turned out
* to be too fragile to do exactly what we need without us having to
* worry about recursive locking in ->prepare_write() and
* ->commit_write(). */
* worry about recursive locking in ->write_begin() and ->write_end(). */
static int ocfs2_write_zero_page(struct inode *inode,
u64 size)
{

4
fs/splice.c
View File

@ -731,8 +731,8 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
};
/*
* The actor worker might be calling ->prepare_write and
* ->commit_write. Most of the time, these expect i_mutex to
* The actor worker might be calling ->write_begin and
* ->write_end. Most of the time, these expect i_mutex to
* be held. Since this may result in an ABBA deadlock with
* pipe->inode, we have to order lock acquiry here.
*/

7
include/linux/fs.h
View File

@ -489,13 +489,6 @@ struct address_space_operations {
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
/*
* ext3 requires that a successful prepare_write() call be followed
* by a commit_write() call - they must be balanced
*/
int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
int (*write_begin)(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata);

242
mm/filemap.c
View File

@ -2029,48 +2029,8 @@ int pagecache_write_begin(struct file *file, struct address_space *mapping,
{
const struct address_space_operations *aops = mapping->a_ops;
if (aops->write_begin) {
return aops->write_begin(file, mapping, pos, len, flags,
return aops->write_begin(file, mapping, pos, len, flags,
pagep, fsdata);
} else {
int ret;
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
struct inode *inode = mapping->host;
struct page *page;
again:
page = __grab_cache_page(mapping, index);
*pagep = page;
if (!page)
return -ENOMEM;
if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
/*
* There is no way to resolve a short write situation
* for a !Uptodate page (except by double copying in
* the caller done by generic_perform_write_2copy).
*
* Instead, we have to bring it uptodate here.
*/
ret = aops->readpage(file, page);
page_cache_release(page);
if (ret) {
if (ret == AOP_TRUNCATED_PAGE)
goto again;
return ret;
}
goto again;
}
ret = aops->prepare_write(file, page, offset, offset+len);
if (ret) {
unlock_page(page);
page_cache_release(page);
if (pos + len > inode->i_size)
vmtruncate(inode, inode->i_size);
}
return ret;
}
}
EXPORT_SYMBOL(pagecache_write_begin);
@ -2079,32 +2039,9 @@ int pagecache_write_end(struct file *file, struct address_space *mapping,
struct page *page, void *fsdata)
{
const struct address_space_operations *aops = mapping->a_ops;
int ret;
if (aops->write_end) {
mark_page_accessed(page);
ret = aops->write_end(file, mapping, pos, len, copied,
page, fsdata);
} else {
unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
struct inode *inode = mapping->host;
flush_dcache_page(page);
ret = aops->commit_write(file, page, offset, offset+len);
unlock_page(page);
mark_page_accessed(page);
page_cache_release(page);
if (ret < 0) {
if (pos + len > inode->i_size)
vmtruncate(inode, inode->i_size);
} else if (ret > 0)
ret = min_t(size_t, copied, ret);
else
ret = copied;
}
return ret;
mark_page_accessed(page);
return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
}
EXPORT_SYMBOL(pagecache_write_end);
@ -2226,174 +2163,6 @@ repeat:
}
EXPORT_SYMBOL(__grab_cache_page);
static ssize_t generic_perform_write_2copy(struct file *file,
struct iov_iter *i, loff_t pos)
{
struct address_space *mapping = file->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
struct inode *inode = mapping->host;
long status = 0;
ssize_t written = 0;
do {
struct page *src_page;
struct page *page;
pgoff_t index; /* Pagecache index for current page */
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
offset = (pos & (PAGE_CACHE_SIZE - 1));
index = pos >> PAGE_CACHE_SHIFT;
bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
iov_iter_count(i));
/*
* a non-NULL src_page indicates that we're doing the
* copy via get_user_pages and kmap.
*/
src_page = NULL;
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*
* Not only is this an optimisation, but it is also required
* to check that the address is actually valid, when atomic
* usercopies are used, below.
*/
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
status = -EFAULT;
break;
}
page = __grab_cache_page(mapping, index);
if (!page) {
status = -ENOMEM;
break;
}
/*
* non-uptodate pages cannot cope with short copies, and we
* cannot take a pagefault with the destination page locked.
* So pin the source page to copy it.
*/
if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) {
unlock_page(page);
src_page = alloc_page(GFP_KERNEL);
if (!src_page) {
page_cache_release(page);
status = -ENOMEM;
break;
}
/*
* Cannot get_user_pages with a page locked for the
* same reason as we can't take a page fault with a
* page locked (as explained below).
*/
copied = iov_iter_copy_from_user(src_page, i,
offset, bytes);
if (unlikely(copied == 0)) {
status = -EFAULT;
page_cache_release(page);
page_cache_release(src_page);
break;
}
bytes = copied;
lock_page(page);
/*
* Can't handle the page going uptodate here, because
* that means we would use non-atomic usercopies, which
* zero out the tail of the page, which can cause
* zeroes to become transiently visible. We could just
* use a non-zeroing copy, but the APIs aren't too
* consistent.
*/
if (unlikely(!page->mapping || PageUptodate(page))) {
unlock_page(page);
page_cache_release(page);
page_cache_release(src_page);
continue;
}
}
status = a_ops->prepare_write(file, page, offset, offset+bytes);
if (unlikely(status))
goto fs_write_aop_error;
if (!src_page) {
/*
* Must not enter the pagefault handler here, because
* we hold the page lock, so we might recursively
* deadlock on the same lock, or get an ABBA deadlock
* against a different lock, or against the mmap_sem
* (which nests outside the page lock). So increment
* preempt count, and use _atomic usercopies.
*
* The page is uptodate so we are OK to encounter a
* short copy: if unmodified parts of the page are
* marked dirty and written out to disk, it doesn't
* really matter.
*/
pagefault_disable();
copied = iov_iter_copy_from_user_atomic(page, i,
offset, bytes);
pagefault_enable();
} else {
void *src, *dst;
src = kmap_atomic(src_page, KM_USER0);
dst = kmap_atomic(page, KM_USER1);
memcpy(dst + offset, src + offset, bytes);
kunmap_atomic(dst, KM_USER1);
kunmap_atomic(src, KM_USER0);
copied = bytes;
}
flush_dcache_page(page);
status = a_ops->commit_write(file, page, offset, offset+bytes);
if (unlikely(status < 0))
goto fs_write_aop_error;
if (unlikely(status > 0)) /* filesystem did partial write */
copied = min_t(size_t, copied, status);
unlock_page(page);
mark_page_accessed(page);
page_cache_release(page);
if (src_page)
page_cache_release(src_page);
iov_iter_advance(i, copied);
pos += copied;
written += copied;
balance_dirty_pages_ratelimited(mapping);
cond_resched();
continue;
fs_write_aop_error:
unlock_page(page);
page_cache_release(page);
if (src_page)
page_cache_release(src_page);
/*
* prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again. Don't need
* i_size_read because we hold i_mutex.
*/
if (pos + bytes > inode->i_size)
vmtruncate(inode, inode->i_size);
break;
} while (iov_iter_count(i));
return written ? written : status;
}
static ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)
{
@ -2494,10 +2263,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
struct iov_iter i;
iov_iter_init(&i, iov, nr_segs, count, written);
if (a_ops->write_begin)
status = generic_perform_write(file, &i, pos);
else
status = generic_perform_write_2copy(file, &i, pos);
status = generic_perform_write(file, &i, pos);
if (likely(status >= 0)) {
written += status;