From: Pavel Emelyanov <[email protected]> The .write_begin and .write_end are requiered to use generic routines (generic_file_aio_write --> ... --> generic_perform_write) for buffered writes.
Changed in v2: - added fuse_wait_on_page_writeback() to fuse ->write_begin; this is crucial to avoid the lost of user data by incorrect crop of a secondary request to a stale inarg->size of the primary. Signed-off-by: Maxim Patlasov <[email protected]> --- fs/fuse/file.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 77eb849..642bd51 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1950,6 +1950,104 @@ out: return err; } +/* + * Determine the number of bytes of data the page contains + */ +static inline unsigned fuse_page_length(struct page *page) +{ + loff_t i_size = i_size_read(page_file_mapping(page)->host); + + if (i_size > 0) { + pgoff_t page_index = page_file_index(page); + pgoff_t end_index = (i_size - 1) >> PAGE_CACHE_SHIFT; + if (page_index < end_index) + return PAGE_CACHE_SIZE; + if (page_index == end_index) + return ((i_size - 1) & ~PAGE_CACHE_MASK) + 1; + } + return 0; +} + +static int fuse_prepare_write(struct fuse_conn *fc, struct file *file, + struct page *page, loff_t pos, unsigned len) +{ + struct fuse_req *req = NULL; + unsigned num_read; + unsigned page_len; + int err; + + if (PageUptodate(page) || (len == PAGE_CACHE_SIZE)) { + fuse_wait_on_page_writeback(page->mapping->host, page->index); + return 0; + } + + page_len = fuse_page_length(page); + if (!page_len) { + fuse_wait_on_page_writeback(page->mapping->host, page->index); + zero_user(page, 0, PAGE_CACHE_SIZE); + return 0; + } + + num_read = __fuse_readpage(file, page, page_len, &err, &req, NULL); + if (req) + fuse_put_request(fc, req); + if (err) { + unlock_page(page); + page_cache_release(page); + } else if (num_read != PAGE_CACHE_SIZE) { + zero_user_segment(page, num_read, PAGE_CACHE_SIZE); + } + return err; +} + +/* + * It's worthy to make sure that space is reserved on disk for the write, + * but how to implement it without killing performance need more thinking. + */ +static int fuse_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + pgoff_t index = pos >> PAGE_CACHE_SHIFT; + struct fuse_conn *fc = get_fuse_conn(file->f_dentry->d_inode); + + BUG_ON(!fc->writeback_cache); + + *pagep = grab_cache_page_write_begin(mapping, index, flags); + if (!*pagep) + return -ENOMEM; + + return fuse_prepare_write(fc, file, *pagep, pos, len); +} + +static int fuse_commit_write(struct file *file, struct page *page, + unsigned from, unsigned to) +{ + struct inode *inode = page->mapping->host; + loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; + + if (!PageUptodate(page)) + SetPageUptodate(page); + + fuse_write_update_size(inode, pos); + set_page_dirty(page); + return 0; +} + +static int fuse_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); + + fuse_commit_write(file, page, from, from+copied); + + unlock_page(page); + page_cache_release(page); + + return copied; +} + static int fuse_launder_page(struct page *page) { int err = 0; @@ -2974,6 +3072,8 @@ static const struct address_space_operations fuse_file_aops = { .set_page_dirty = __set_page_dirty_nobuffers, .bmap = fuse_bmap, .direct_IO = fuse_direct_IO, + .write_begin = fuse_write_begin, + .write_end = fuse_write_end, }; void fuse_init_file_inode(struct inode *inode) _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
