From ae259a9c8593f98aa60d045df978a5482a67c53f Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 21 Jun 2016 09:23:11 +1000 Subject: fs: introduce iomap infrastructure Add infrastructure for multipage buffered writes. This is implemented using an main iterator that applies an actor function to a range that can be written. This infrastucture is used to implement a buffered write helper, one to zero file ranges and one to implement the ->page_mkwrite VM operations. All of them borrow a fair amount of code from fs/buffers. for now by using an internal version of __block_write_begin that gets passed an iomap and builds the corresponding buffer head. The file system is gets a set of paired ->iomap_begin and ->iomap_end calls which allow it to map/reserve a range and get a notification once the write code is finished with it. Based on earlier code from Dave Chinner. Signed-off-by: Christoph Hellwig Reviewed-by: Bob Peterson Signed-off-by: Dave Chinner --- fs/buffer.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 71 insertions(+), 5 deletions(-) (limited to 'fs/buffer.c') diff --git a/fs/buffer.c b/fs/buffer.c index 754813a6962b..228288a7de38 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -1891,8 +1892,62 @@ void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) } EXPORT_SYMBOL(page_zero_new_buffers); -int __block_write_begin(struct page *page, loff_t pos, unsigned len, - get_block_t *get_block) +static void +iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh, + struct iomap *iomap) +{ + loff_t offset = block << inode->i_blkbits; + + bh->b_bdev = iomap->bdev; + + /* + * Block points to offset in file we need to map, iomap contains + * the offset at which the map starts. If the map ends before the + * current block, then do not map the buffer and let the caller + * handle it. + */ + BUG_ON(offset >= iomap->offset + iomap->length); + + switch (iomap->type) { + case IOMAP_HOLE: + /* + * If the buffer is not up to date or beyond the current EOF, + * we need to mark it as new to ensure sub-block zeroing is + * executed if necessary. + */ + if (!buffer_uptodate(bh) || + (offset >= i_size_read(inode))) + set_buffer_new(bh); + break; + case IOMAP_DELALLOC: + if (!buffer_uptodate(bh) || + (offset >= i_size_read(inode))) + set_buffer_new(bh); + set_buffer_uptodate(bh); + set_buffer_mapped(bh); + set_buffer_delay(bh); + break; + case IOMAP_UNWRITTEN: + /* + * For unwritten regions, we always need to ensure that + * sub-block writes cause the regions in the block we are not + * writing to are zeroed. Set the buffer as new to ensure this. + */ + set_buffer_new(bh); + set_buffer_unwritten(bh); + /* FALLTHRU */ + case IOMAP_MAPPED: + if (offset >= i_size_read(inode)) + set_buffer_new(bh); + bh->b_blocknr = (iomap->blkno >> (inode->i_blkbits - 9)) + + ((offset - iomap->offset) >> inode->i_blkbits); + set_buffer_mapped(bh); + break; + } +} + +int __block_write_begin_int(struct page *page, loff_t pos, unsigned len, + get_block_t *get_block, struct iomap *iomap) { unsigned from = pos & (PAGE_SIZE - 1); unsigned to = from + len; @@ -1928,9 +1983,14 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len, clear_buffer_new(bh); if (!buffer_mapped(bh)) { WARN_ON(bh->b_size != blocksize); - err = get_block(inode, block, bh, 1); - if (err) - break; + if (get_block) { + err = get_block(inode, block, bh, 1); + if (err) + break; + } else { + iomap_to_bh(inode, block, bh, iomap); + } + if (buffer_new(bh)) { unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); @@ -1971,6 +2031,12 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len, page_zero_new_buffers(page, from, to); return err; } + +int __block_write_begin(struct page *page, loff_t pos, unsigned len, + get_block_t *get_block) +{ + return __block_write_begin_int(page, pos, len, get_block, NULL); +} EXPORT_SYMBOL(__block_write_begin); static int __block_commit_write(struct inode *inode, struct page *page, -- cgit