From 03158cd7eb3374843de68421142ca5900df845d9 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 16 Oct 2007 01:25:25 -0700 Subject: fs: restore nobh Implement nobh in new aops. This is a bit tricky. FWIW, nobh_truncate is now implemented in a way that does not create blocks in sparse regions, which is a silly thing for it to have been doing (isn't it?) ext2 survives fsx and fsstress. jfs is converted as well... ext3 should be easy to do (but not done yet). [akpm@linux-foundation.org: coding-style fixes] Cc: Badari Pulavarty Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/buffer.c | 229 +++++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 150 insertions(+), 79 deletions(-) (limited to 'fs/buffer.c') diff --git a/fs/buffer.c b/fs/buffer.c index a89d25bf117..a406cfd89e3 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2369,7 +2369,7 @@ out_unlock: } /* - * nobh_prepare_write()'s prereads are special: the buffer_heads are freed + * nobh_write_begin()'s prereads are special: the buffer_heads are freed * immediately, while under the page lock. So it needs a special end_io * handler which does not touch the bh after unlocking it. */ @@ -2378,17 +2378,46 @@ static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) __end_buffer_read_notouch(bh, uptodate); } +/* + * Attach the singly-linked list of buffers created by nobh_write_begin, to + * the page (converting it to circular linked list and taking care of page + * dirty races). + */ +static void attach_nobh_buffers(struct page *page, struct buffer_head *head) +{ + struct buffer_head *bh; + + BUG_ON(!PageLocked(page)); + + spin_lock(&page->mapping->private_lock); + bh = head; + do { + if (PageDirty(page)) + set_buffer_dirty(bh); + if (!bh->b_this_page) + bh->b_this_page = head; + bh = bh->b_this_page; + } while (bh != head); + attach_page_buffers(page, head); + spin_unlock(&page->mapping->private_lock); +} + /* * On entry, the page is fully not uptodate. * On exit the page is fully uptodate in the areas outside (from,to) */ -int nobh_prepare_write(struct page *page, unsigned from, unsigned to, +int nobh_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata, get_block_t *get_block) { - struct inode *inode = page->mapping->host; + struct inode *inode = mapping->host; const unsigned blkbits = inode->i_blkbits; const unsigned blocksize = 1 << blkbits; struct buffer_head *head, *bh; + struct page *page; + pgoff_t index; + unsigned from, to; unsigned block_in_page; unsigned block_start, block_end; sector_t block_in_file; @@ -2397,8 +2426,23 @@ int nobh_prepare_write(struct page *page, unsigned from, unsigned to, int ret = 0; int is_mapped_to_disk = 1; - if (page_has_buffers(page)) - return block_prepare_write(page, from, to, get_block); + index = pos >> PAGE_CACHE_SHIFT; + from = pos & (PAGE_CACHE_SIZE - 1); + to = from + len; + + page = __grab_cache_page(mapping, index); + if (!page) + return -ENOMEM; + *pagep = page; + *fsdata = NULL; + + if (page_has_buffers(page)) { + unlock_page(page); + page_cache_release(page); + *pagep = NULL; + return block_write_begin(file, mapping, pos, len, flags, pagep, + fsdata, get_block); + } if (PageMappedToDisk(page)) return 0; @@ -2413,8 +2457,10 @@ int nobh_prepare_write(struct page *page, unsigned from, unsigned to, * than the circular one we're used to. */ head = alloc_page_buffers(page, blocksize, 0); - if (!head) - return -ENOMEM; + if (!head) { + ret = -ENOMEM; + goto out_release; + } block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); @@ -2483,15 +2529,12 @@ int nobh_prepare_write(struct page *page, unsigned from, unsigned to, if (is_mapped_to_disk) SetPageMappedToDisk(page); - do { - bh = head; - head = head->b_this_page; - free_buffer_head(bh); - } while (head); + *fsdata = head; /* to be released by nobh_write_end */ return 0; failed: + BUG_ON(!ret); /* * Error recovery is a bit difficult. We need to zero out blocks that * were newly allocated, and dirty them to ensure they get written out. @@ -2499,64 +2542,57 @@ failed: * the handling of potential IO errors during writeout would be hard * (could try doing synchronous writeout, but what if that fails too?) */ - spin_lock(&page->mapping->private_lock); - bh = head; - block_start = 0; - do { - if (PageUptodate(page)) - set_buffer_uptodate(bh); - if (PageDirty(page)) - set_buffer_dirty(bh); + attach_nobh_buffers(page, head); + page_zero_new_buffers(page, from, to); - block_end = block_start+blocksize; - if (block_end <= from) - goto next; - if (block_start >= to) - goto next; +out_release: + unlock_page(page); + page_cache_release(page); + *pagep = NULL; - if (buffer_new(bh)) { - clear_buffer_new(bh); - if (!buffer_uptodate(bh)) { - zero_user_page(page, block_start, bh->b_size, KM_USER0); - set_buffer_uptodate(bh); - } - mark_buffer_dirty(bh); - } -next: - block_start = block_end; - if (!bh->b_this_page) - bh->b_this_page = head; - bh = bh->b_this_page; - } while (bh != head); - attach_page_buffers(page, head); - spin_unlock(&page->mapping->private_lock); + if (pos + len > inode->i_size) + vmtruncate(inode, inode->i_size); return ret; } -EXPORT_SYMBOL(nobh_prepare_write); +EXPORT_SYMBOL(nobh_write_begin); -/* - * Make sure any changes to nobh_commit_write() are reflected in - * nobh_truncate_page(), since it doesn't call commit_write(). - */ -int nobh_commit_write(struct file *file, struct page *page, - unsigned from, unsigned to) +int nobh_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) { struct inode *inode = page->mapping->host; - loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; + struct buffer_head *head = NULL; + struct buffer_head *bh; - if (page_has_buffers(page)) - return generic_commit_write(file, page, from, to); + if (!PageMappedToDisk(page)) { + if (unlikely(copied < len) && !page_has_buffers(page)) + attach_nobh_buffers(page, head); + if (page_has_buffers(page)) + return generic_write_end(file, mapping, pos, len, + copied, page, fsdata); + } SetPageUptodate(page); set_page_dirty(page); - if (pos > inode->i_size) { - i_size_write(inode, pos); + if (pos+copied > inode->i_size) { + i_size_write(inode, pos+copied); mark_inode_dirty(inode); } - return 0; + + unlock_page(page); + page_cache_release(page); + + head = fsdata; + while (head) { + bh = head; + head = head->b_this_page; + free_buffer_head(bh); + } + + return copied; } -EXPORT_SYMBOL(nobh_commit_write); +EXPORT_SYMBOL(nobh_write_end); /* * nobh_writepage() - based on block_full_write_page() except @@ -2609,44 +2645,79 @@ out: } EXPORT_SYMBOL(nobh_writepage); -/* - * This function assumes that ->prepare_write() uses nobh_prepare_write(). - */ -int nobh_truncate_page(struct address_space *mapping, loff_t from) +int nobh_truncate_page(struct address_space *mapping, + loff_t from, get_block_t *get_block) { - struct inode *inode = mapping->host; - unsigned blocksize = 1 << inode->i_blkbits; pgoff_t index = from >> PAGE_CACHE_SHIFT; unsigned offset = from & (PAGE_CACHE_SIZE-1); - unsigned to; + unsigned blocksize; + sector_t iblock; + unsigned length, pos; + struct inode *inode = mapping->host; struct page *page; - const struct address_space_operations *a_ops = mapping->a_ops; - int ret = 0; + struct buffer_head map_bh; + int err; - if ((offset & (blocksize - 1)) == 0) - goto out; + blocksize = 1 << inode->i_blkbits; + length = offset & (blocksize - 1); + + /* Block boundary? Nothing to do */ + if (!length) + return 0; + + length = blocksize - length; + iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); - ret = -ENOMEM; page = grab_cache_page(mapping, index); + err = -ENOMEM; if (!page) goto out; - to = (offset + blocksize) & ~(blocksize - 1); - ret = a_ops->prepare_write(NULL, page, offset, to); - if (ret == 0) { - zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, - KM_USER0); - /* - * It would be more correct to call aops->commit_write() - * here, but this is more efficient. - */ - SetPageUptodate(page); - set_page_dirty(page); + if (page_has_buffers(page)) { +has_buffers: + unlock_page(page); + page_cache_release(page); + return block_truncate_page(mapping, from, get_block); } + + /* Find the buffer that contains "offset" */ + pos = blocksize; + while (offset >= pos) { + iblock++; + pos += blocksize; + } + + err = get_block(inode, iblock, &map_bh, 0); + if (err) + goto unlock; + /* unmapped? It's a hole - nothing to do */ + if (!buffer_mapped(&map_bh)) + goto unlock; + + /* Ok, it's mapped. Make sure it's up-to-date */ + if (!PageUptodate(page)) { + err = mapping->a_ops->readpage(NULL, page); + if (err) { + page_cache_release(page); + goto out; + } + lock_page(page); + if (!PageUptodate(page)) { + err = -EIO; + goto unlock; + } + if (page_has_buffers(page)) + goto has_buffers; + } + zero_user_page(page, offset, length, KM_USER0); + set_page_dirty(page); + err = 0; + +unlock: unlock_page(page); page_cache_release(page); out: - return ret; + return err; } EXPORT_SYMBOL(nobh_truncate_page); -- cgit v1.2.3