diff options
| -rw-r--r-- | fs/ext4/ext4.h | 11 | ||||
| -rw-r--r-- | fs/ext4/inode.c | 224 |
2 files changed, 235 insertions, 0 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 5c38120c389c..ccfa81f33bb0 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -529,6 +529,11 @@ struct ext4_new_group_data { #define EXT4_FREE_BLOCKS_NO_QUOT_UPDATE 0x0008 /* + * Flags used by ext4_discard_partial_page_buffers + */ +#define EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED 0x0001 + +/* * ioctl commands */ #define EXT4_IOC_GETFLAGS FS_IOC_GETFLAGS @@ -1838,6 +1843,12 @@ extern int ext4_block_truncate_page(handle_t *handle, struct address_space *mapping, loff_t from); extern int ext4_block_zero_page_range(handle_t *handle, struct address_space *mapping, loff_t from, loff_t length); +extern int ext4_discard_partial_page_buffers(handle_t *handle, + struct address_space *mapping, loff_t from, + loff_t length, int flags); +extern int ext4_discard_partial_page_buffers_no_lock(handle_t *handle, + struct inode *inode, struct page *page, loff_t from, + loff_t length, int flags); extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf); extern qsize_t *ext4_get_reserved_space(struct inode *inode); extern void ext4_da_update_reserve_space(struct inode *inode, diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index b84f127c085d..d1b1ef71e5b7 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2966,6 +2966,230 @@ void ext4_set_aops(struct inode *inode) inode->i_mapping->a_ops = &ext4_journalled_aops; } + +/* + * ext4_discard_partial_page_buffers() + * Wrapper function for ext4_discard_partial_page_buffers_no_lock. + * This function finds and locks the page containing the offset + * "from" and passes it to ext4_discard_partial_page_buffers_no_lock. + * Calling functions that already have the page locked should call + * ext4_discard_partial_page_buffers_no_lock directly. + */ +int ext4_discard_partial_page_buffers(handle_t *handle, + struct address_space *mapping, loff_t from, + loff_t length, int flags) +{ + struct inode *inode = mapping->host; + struct page *page; + int err = 0; + + page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT, + mapping_gfp_mask(mapping) & ~__GFP_FS); + if (!page) + return -EINVAL; + + err = ext4_discard_partial_page_buffers_no_lock(handle, inode, page, + from, length, flags); + + unlock_page(page); + page_cache_release(page); + return err; +} + +/* + * ext4_discard_partial_page_buffers_no_lock() + * Zeros a page range of length 'length' starting from offset 'from'. + * Buffer heads that correspond to the block aligned regions of the + * zeroed range will be unmapped. Unblock aligned regions + * will have the corresponding buffer head mapped if needed so that + * that region of the page can be updated with the partial zero out. + * + * This function assumes that the page has already been locked. The + * The range to be discarded must be contained with in the given page. + * If the specified range exceeds the end of the page it will be shortened + * to the end of the page that corresponds to 'from'. This function is + * appropriate for updating a page and it buffer heads to be unmapped and + * zeroed for blocks that have been either released, or are going to be + * released. + * + * handle: The journal handle + * inode: The files inode + * page: A locked page that contains the offset "from" + * from: The starting byte offset (from the begining of the file) + * to begin discarding + * len: The length of bytes to discard + * flags: Optional flags that may be used: + * + * EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED + * Only zero the regions of the page whose buffer heads + * have already been unmapped. This flag is appropriate + * for updateing the contents of a page whose blocks may + * have already been released, and we only want to zero + * out the regions that correspond to those released blocks. + * + * Returns zero on sucess or negative on failure. + */ +int ext4_discard_partial_page_buffers_no_lock(handle_t *handle, + struct inode *inode, struct page *page, loff_t from, + loff_t length, int flags) +{ + ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT; + unsigned int offset = from & (PAGE_CACHE_SIZE-1); + unsigned int blocksize, max, pos; + unsigned int end_of_block, range_to_discard; + ext4_lblk_t iblock; + struct buffer_head *bh; + int err = 0; + + blocksize = inode->i_sb->s_blocksize; + max = PAGE_CACHE_SIZE - offset; + + if (index != page->index) + return -EINVAL; + + /* + * correct length if it does not fall between + * 'from' and the end of the page + */ + if (length > max || length < 0) + length = max; + + iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits); + + if (!page_has_buffers(page)) { + /* + * If the range to be discarded covers a partial block + * we need to get the page buffers. This is because + * partial blocks cannot be released and the page needs + * to be updated with the contents of the block before + * we write the zeros on top of it. + */ + if (!(from & (blocksize - 1)) || + !((from + length) & (blocksize - 1))) { + create_empty_buffers(page, blocksize, 0); + } else { + /* + * If there are no partial blocks, + * there is nothing to update, + * so we can return now + */ + return 0; + } + } + + /* Find the buffer that contains "offset" */ + bh = page_buffers(page); + pos = blocksize; + while (offset >= pos) { + bh = bh->b_this_page; + iblock++; + pos += blocksize; + } + + pos = offset; + while (pos < offset + length) { + err = 0; + + /* The length of space left to zero and unmap */ + range_to_discard = offset + length - pos; + + /* The length of space until the end of the block */ + end_of_block = blocksize - (pos & (blocksize-1)); + + /* + * Do not unmap or zero past end of block + * for this buffer head + */ + if (range_to_discard > end_of_block) + range_to_discard = end_of_block; + + + /* + * Skip this buffer head if we are only zeroing unampped + * regions of the page + */ + if (flags & EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED && + buffer_mapped(bh)) + goto next; + + /* If the range is block aligned, unmap */ + if (range_to_discard == blocksize) { + clear_buffer_dirty(bh); + bh->b_bdev = NULL; + clear_buffer_mapped(bh); + clear_buffer_req(bh); + clear_buffer_new(bh); + clear_buffer_delay(bh); + clear_buffer_unwritten(bh); + clear_buffer_uptodate(bh); + zero_user(page, pos, range_to_discard); + BUFFER_TRACE(bh, "Buffer discarded"); + goto next; + } + + /* + * If this block is not completely contained in the range + * to be discarded, then it is not going to be released. Because + * we need to keep this block, we need to make sure this part + * of the page is uptodate before we modify it by writeing + * partial zeros on it. + */ + if (!buffer_mapped(bh)) { + /* + * Buffer head must be mapped before we can read + * from the block + */ + BUFFER_TRACE(bh, "unmapped"); + ext4_get_block(inode, iblock, bh, 0); + /* unmapped? It's a hole - nothing to do */ + if (!buffer_mapped(bh)) { + BUFFER_TRACE(bh, "still unmapped"); + goto next; + } + } + + /* Ok, it's mapped. Make sure it's up-to-date */ + if (PageUptodate(page)) + set_buffer_uptodate(bh); + + if (!buffer_uptodate(bh)) { + err = -EIO; + ll_rw_block(READ, 1, &bh); + wait_on_buffer(bh); + /* Uhhuh. Read error. Complain and punt.*/ + if (!buffer_uptodate(bh)) + goto next; + } + + if (ext4_should_journal_data(inode)) { + BUFFER_TRACE(bh, "get write access"); + err = ext4_journal_get_write_access(handle, bh); + if (err) + goto next; + } + + zero_user(page, pos, range_to_discard); + + err = 0; + if (ext4_should_journal_data(inode)) { + err = ext4_handle_dirty_metadata(handle, inode, bh); + } else { + if (ext4_should_order_data(inode) && + EXT4_I(inode)->jinode) + err = ext4_jbd2_file_inode(handle, inode); + mark_buffer_dirty(bh); + } + + BUFFER_TRACE(bh, "Partial buffer zeroed"); +next: + bh = bh->b_this_page; + iblock++; + pos += range_to_discard; + } + + return err; +} + /* * ext4_block_truncate_page() zeroes out a mapping from file offset `from' * up to the end of the block which corresponds to `from'. |