diff options
| -rw-r--r-- | Documentation/filesystems/Locking | 9 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 45 | ||||
| -rw-r--r-- | drivers/block/loop.c | 75 | ||||
| -rw-r--r-- | fs/buffer.c | 201 | ||||
| -rw-r--r-- | fs/libfs.c | 44 | ||||
| -rw-r--r-- | fs/namei.c | 46 | ||||
| -rw-r--r-- | fs/splice.c | 69 | ||||
| -rw-r--r-- | include/linux/buffer_head.h | 10 | ||||
| -rw-r--r-- | include/linux/fs.h | 30 | ||||
| -rw-r--r-- | include/linux/pagemap.h | 2 | ||||
| -rw-r--r-- | mm/filemap.c | 250 |
11 files changed, 575 insertions, 206 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index f0f8258..fe26cc9 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -178,15 +178,18 @@ prototypes: locking rules: All except set_page_dirty may block - BKL PageLocked(page) + BKL PageLocked(page) i_sem writepage: no yes, unlocks (see below) readpage: no yes, unlocks sync_page: no maybe writepages: no set_page_dirty no no readpages: no -prepare_write: no yes -commit_write: no yes +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 bmap: yes invalidatepage: no yes releasepage: no yes diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 045f3e0..281c19f 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -537,6 +537,12 @@ struct address_space_operations { 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); @@ -633,6 +639,45 @@ struct address_space_operations { 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). + + 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, + 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 filesystem must return the locked pagecache page for the specified + offset, in *pagep, for the caller to write into. + + flags is a field for AOP_FLAG_xxx flags, described in + include/linux/fs.h. + + A void * may be returned in fsdata, which then gets passed into + write_end. + + Returns 0 on success; < 0 on failure (which is the error code), in + which case write_end is not called. + + write_end: After a successful write_begin, and data copy, write_end must + be called. len is the original len passed to write_begin, and copied + is the amount that was able to be copied (copied == len is always true + if write_begin was called with the AOP_FLAG_UNINTERRUPTIBLE flag). + + The filesystem must take care of unlocking the page and releasing it + refcount, and updating i_size. + + Returns < 0 on failure, otherwise the number of bytes (<= 'copied') + that were able to be copied into pagecache. + bmap: called by the VFS to map a logical block offset within object to physical block number. This method is used by the FIBMAP ioctl and for working with swap-files. To be able to swap to diff --git a/drivers/block/loop.c b/drivers/block/loop.c index b9233a0..a5f993a 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -204,14 +204,13 @@ lo_do_transfer(struct loop_device *lo, int cmd, * do_lo_send_aops - helper for writing data to a loop device * * This is the fast version for backing filesystems which implement the address - * space operations prepare_write and commit_write. + * space operations write_begin and write_end. */ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, - int bsize, loff_t pos, struct page *page) + int bsize, loff_t pos, struct page *unused) { struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */ struct address_space *mapping = file->f_mapping; - const struct address_space_operations *aops = mapping->a_ops; pgoff_t index; unsigned offset, bv_offs; int len, ret; @@ -223,63 +222,47 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, len = bvec->bv_len; while (len > 0) { sector_t IV; - unsigned size; + unsigned size, copied; int transfer_result; + struct page *page; + void *fsdata; IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9); size = PAGE_CACHE_SIZE - offset; if (size > len) size = len; - page = grab_cache_page(mapping, index); - if (unlikely(!page)) + + ret = pagecache_write_begin(file, mapping, pos, size, 0, + &page, &fsdata); + if (ret) goto fail; - ret = aops->prepare_write(file, page, offset, - offset + size); - if (unlikely(ret)) { - if (ret == AOP_TRUNCATED_PAGE) { - page_cache_release(page); - continue; - } - goto unlock; - } + transfer_result = lo_do_transfer(lo, WRITE, page, offset, bvec->bv_page, bv_offs, size, IV); - if (unlikely(transfer_result)) { - /* - * The transfer failed, but we still write the data to - * keep prepare/commit calls balanced. - */ - printk(KERN_ERR "loop: transfer error block %llu\n", - (unsigned long long)index); - zero_user_page(page, offset, size, KM_USER0); - } - flush_dcache_page(page); - ret = aops->commit_write(file, page, offset, - offset + size); - if (unlikely(ret)) { - if (ret == AOP_TRUNCATED_PAGE) { - page_cache_release(page); - continue; - } - goto unlock; - } + copied = size; if (unlikely(transfer_result)) - goto unlock; - bv_offs += size; - len -= size; + copied = 0; + + ret = pagecache_write_end(file, mapping, pos, size, copied, + page, fsdata); + if (ret < 0) + goto fail; + if (ret < copied) + copied = ret; + + if (unlikely(transfer_result)) + goto fail; + + bv_offs += copied; + len -= copied; offset = 0; index++; - pos += size; - unlock_page(page); - page_cache_release(page); + pos += copied; } ret = 0; out: mutex_unlock(&mapping->host->i_mutex); return ret; -unlock: - unlock_page(page); - page_cache_release(page); fail: ret = -1; goto out; @@ -313,7 +296,7 @@ static int __do_lo_send_write(struct file *file, * do_lo_send_direct_write - helper for writing data to a loop device * * This is the fast, non-transforming version for backing filesystems which do - * not implement the address space operations prepare_write and commit_write. + * not implement the address space operations write_begin and write_end. * It uses the write file operation which should be present on all writeable * filesystems. */ @@ -332,7 +315,7 @@ static int do_lo_send_direct_write(struct loop_device *lo, * do_lo_send_write - helper for writing data to a loop device * * This is the slow, transforming version for filesystems which do not - * implement the address space operations prepare_write and commit_write. It + * implement the address space operations write_begin and write_end. It * uses the write file operation which should be present on all writeable * filesystems. * @@ -780,7 +763,7 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file, */ if (!file->f_op->splice_read) goto out_putf; - if (aops->prepare_write && aops->commit_write) + if (aops->prepare_write || 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; diff --git a/fs/buffer.c b/fs/buffer.c index 9ece6c2..68b8fbd 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1770,6 +1770,48 @@ recover: goto done; } +/* + * If a page has any new buffers, zero them out here, and mark them uptodate + * and dirty so they'll be written out (in order to prevent uninitialised + * block data from leaking). And clear the new bit. + */ +void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) +{ + unsigned int block_start, block_end; + struct buffer_head *head, *bh; + + BUG_ON(!PageLocked(page)); + if (!page_has_buffers(page)) + return; + + bh = head = page_buffers(page); + block_start = 0; + do { + block_end = block_start + bh->b_size; + + if (buffer_new(bh)) { + if (block_end > from && block_start < to) { + if (!PageUptodate(page)) { + unsigned start, size; + + start = max(from, block_start); + size = min(to, block_end) - start; + + zero_user_page(page, start, size, KM_USER0); + set_buffer_uptodate(bh); + } + + clear_buffer_new(bh); + mark_buffer_dirty(bh); + } + } + + block_start = block_end; + bh = bh->b_this_page; + } while (bh != head); +} +EXPORT_SYMBOL(page_zero_new_buffers); + static int __block_prepare_write(struct inode *inode, struct page *page, unsigned from, unsigned to, get_block_t *get_block) { @@ -1854,38 +1896,8 @@ static int __block_prepare_write(struct inode *inode, struct page *page, if (!buffer_uptodate(*wait_bh)) err = -EIO; } - if (!err) { - bh = head; - do { - if (buffer_new(bh)) - clear_buffer_new(bh); - } while ((bh = bh->b_this_page) != head); - return 0; - } - /* Error case: */ - /* - * Zero out any newly allocated blocks to avoid exposing stale - * data. If BH_New is set, we know that the block was newly - * allocated in the above loop. - */ - bh = head; - block_start = 0; - do { - block_end = block_start+blocksize; - if (block_end <= from) - goto next_bh; - if (block_start >= to) - break; - if (buffer_new(bh)) { - clear_buffer_new(bh); - zero_user_page(page, block_start, bh->b_size, KM_USER0); - set_buffer_uptodate(bh); - mark_buffer_dirty(bh); - } -next_bh: - block_start = block_end; - bh = bh->b_this_page; - } while (bh != head); + if (unlikely(err)) + page_zero_new_buffers(page, from, to); return err; } @@ -1910,6 +1922,7 @@ static int __block_commit_write(struct inode *inode, struct page *page, set_buffer_uptodate(bh); mark_buffer_dirty(bh); } + clear_buffer_new(bh); } /* @@ -1924,6 +1937,130 @@ static int __block_commit_write(struct inode *inode, struct page *page, } /* + * block_write_begin takes care of the basic task of block allocation and + * bringing partial write blocks uptodate first. + * + * If *pagep is not NULL, then block_write_begin uses the locked page + * at *pagep rather than allocating its own. In this case, the page will + * not be unlocked or deallocated on failure. + */ +int block_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 = mapping->host; + int status = 0; + struct page *page; + pgoff_t index; + unsigned start, end; + int ownpage = 0; + + index = pos >> PAGE_CACHE_SHIFT; + start = pos & (PAGE_CACHE_SIZE - 1); + end = start + len; + + page = *pagep; + if (page == NULL) { + ownpage = 1; + page = __grab_cache_page(mapping, index); + if (!page) { + status = -ENOMEM; + goto out; + } + *pagep = page; + } else + BUG_ON(!PageLocked(page)); + + status = __block_prepare_write(inode, page, start, end, get_block); + if (unlikely(status)) { + ClearPageUptodate(page); + + if (ownpage) { + unlock_page(page); + page_cache_release(page); + *pagep = NULL; + + /* + * 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 + len > inode->i_size) + vmtruncate(inode, inode->i_size); + } + goto out; + } + +out: + return status; +} +EXPORT_SYMBOL(block_write_begin); + +int block_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + struct inode *inode = mapping->host; + unsigned start; + + start = pos & (PAGE_CACHE_SIZE - 1); + + if (unlikely(copied < len)) { + /* + * The buffers that were written will now be uptodate, so we + * don't have to worry about a readpage reading them and + * overwriting a partial write. However if we have encountered + * a short write and only partially written into a buffer, it + * will not be marked uptodate, so a readpage might come in and + * destroy our partial write. + * + * Do the simplest thing, and just treat any short write to a + * non uptodate page as a zero-length write, and force the + * caller to redo the whole thing. + */ + if (!PageUptodate(page)) + copied = 0; + + page_zero_new_buffers(page, start+copied, start+len); + } + flush_dcache_page(page); + + /* This could be a short (even 0-length) commit */ + __block_commit_write(inode, page, start, start+copied); + + return copied; +} +EXPORT_SYMBOL(block_write_end); + +int generic_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + struct inode *inode = mapping->host; + + copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); + + /* + * No need to use i_size_read() here, the i_size + * cannot change under us because we hold i_mutex. + * + * But it's important to update i_size while still holding page lock: + * page writeout could otherwise come in and zero beyond i_size. + */ + if (pos+copied > inode->i_size) { + i_size_write(inode, pos+copied); + mark_inode_dirty(inode); + } + + unlock_page(page); + page_cache_release(page); + + return copied; +} +EXPORT_SYMBOL(generic_write_end); + +/* * Generic "read page" function for block devices that have the normal * get_block functionality. This is most of the block device filesystems. * Reads the page asynchronously --- the unlock_buffer() and @@ -351,6 +351,26 @@ int simple_prepare_write(struct file *file, struct page *page, return 0; } +int simple_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + struct page *page; + pgoff_t index; + unsigned from; + + index = pos >> PAGE_CACHE_SHIFT; + from = pos & (PAGE_CACHE_SIZE - 1); + + page = __grab_cache_page(mapping, index); + if (!page) + return -ENOMEM; + + *pagep = page; + + return simple_prepare_write(file, page, from, from+len); +} + int simple_commit_write(struct file *file, struct page *page, unsigned from, unsigned to) { @@ -369,6 +389,28 @@ int simple_commit_write(struct file *file, struct page *page, return 0; } +int simple_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); + + /* zero the stale part of the page if we did a short copy */ + if (copied < len) { + void *kaddr = kmap_atomic(page, KM_USER0); + memset(kaddr + from + copied, 0, len - copied); + flush_dcache_page(page); + kunmap_atomic(kaddr, KM_USER0); + } + + simple_commit_write(file, page, from, from+copied); + + unlock_page(page); + page_cache_release(page); + + return copied; +} + /* * the inodes created here are not hashed. If you use iunique to generate * unique inode values later for this filesystem, then you must take care @@ -642,6 +684,8 @@ EXPORT_SYMBOL(dcache_dir_open); EXPORT_SYMBOL(dcache_readdir); EXPORT_SYMBOL(generic_read_dir); EXPORT_SYMBOL(get_sb_pseudo); +EXPORT_SYMBOL(simple_write_begin); +EXPORT_SYMBOL(simple_write_end); EXPORT_SYMBOL(simple_commit_write); EXPORT_SYMBOL(simple_dir_inode_operations); EXPORT_SYMBOL(simple_dir_operations); @@ -2729,53 +2729,29 @@ int __page_symlink(struct inode *inode, const char *symname, int len, { struct address_space *mapping = inode->i_mapping; struct page *page; + void *fsdata; int err; char *kaddr; retry: - err = -ENOMEM; - page = find_or_create_page(mapping, 0, gfp_mask); - if (!page) - goto fail; - err = mapping->a_ops->prepare_write(NULL, page, 0, len-1); - if (err == AOP_TRUNCATED_PAGE) { - page_cache_release(page); - goto retry; - } + err = pagecache_write_begin(NULL, mapping, 0, len-1, + AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); if (err) - goto fail_map; + goto fail; + kaddr = kmap_atomic(page, KM_USER0); memcpy(kaddr, symname, len-1); kunmap_atomic(kaddr, KM_USER0); - err = mapping->a_ops->commit_write(NULL, page, 0, len-1); - if (err == AOP_TRUNCATED_PAGE) { - page_cache_release(page); - goto retry; - } - if (err) - goto fail_map; - /* - * Notice that we are _not_ going to block here - end of page is - * unmapped, so this will only try to map the rest of page, see - * that it is unmapped (typically even will not look into inode - - * ->i_size will be enough for everything) and zero it out. - * OTOH it's obviously correct and should make the page up-to-date. - */ - if (!PageUptodate(page)) { - err = mapping->a_ops->readpage(NULL, page); - if (err != AOP_TRUNCATED_PAGE) - wait_on_page_locked(page); - } else { - unlock_page(page); - } - page_cache_release(page); + + err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, + page, fsdata); if (err < 0) goto fail; + if (err < len-1) + goto retry; + mark_inode_dirty(inode); return 0; -fail_map: - unlock_page(page); - page_cache_release(page); fail: return err; } diff --git a/fs/splice.c b/fs/splice.c index 2df6be4..a7568bc 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -563,7 +563,7 @@ static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct address_space *mapping = file->f_mapping; unsigned int offset, this_len; struct page *page; - pgoff_t index; + void *fsdata; int ret; /* @@ -573,49 +573,16 @@ static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, if (unlikely(ret)) return ret; - index = sd->pos >> PAGE_CACHE_SHIFT; offset = sd->pos & ~PAGE_CACHE_MASK; this_len = sd->len; if (this_len + offset > PAGE_CACHE_SIZE) this_len = PAGE_CACHE_SIZE - offset; -find_page: - page = find_lock_page(mapping, index); - if (!page) { - ret = -ENOMEM; - page = page_cache_alloc_cold(mapping); - if (unlikely(!page)) - goto out_ret; - - /* - * This will also lock the page - */ - ret = add_to_page_cache_lru(page, mapping, index, - GFP_KERNEL); - if (unlikely(ret)) - goto out_release; - } - - ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len); - if (unlikely(ret)) { - loff_t isize = i_size_read(mapping->host); - - if (ret != AOP_TRUNCATED_PAGE) - unlock_page(page); - page_cache_release(page); - if (ret == AOP_TRUNCATED_PAGE) - goto find_page; - - /* - * prepare_write() may have instantiated a few blocks - * outside i_size. Trim these off again. - */ - if (sd->pos + this_len > isize) - vmtruncate(mapping->host, isize); - - goto out_ret; - } + ret = pagecache_write_begin(file, mapping, sd->pos, this_len, + AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); + if (unlikely(ret)) + goto out; if (buf->page != page) { /* @@ -629,31 +596,9 @@ find_page: kunmap_atomic(dst, KM_USER1); buf->ops->unmap(pipe, buf, src); } - - ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len); - if (ret) { - if (ret == AOP_TRUNCATED_PAGE) { - page_cache_release(page); - goto find_page; - } - if (ret < 0) - goto out; - /* - * Partial write has happened, so 'ret' already initialized by - * number of bytes written, Where is nothing we have to do here. - */ - } else - ret = this_len; - /* - * Return the number of bytes written and mark page as - * accessed, we are now done! - */ - mark_page_accessed(page); + ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len, + page, fsdata); out: - unlock_page(page); -out_release: - page_cache_release(page); -out_ret: return ret; } diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 35cadad..a562ecf 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -203,6 +203,16 @@ void block_invalidatepage(struct page *page, unsigned long offset); int block_write_full_page(struct page *page, get_block_t *get_block, struct writeback_control *wbc); int block_read_full_page(struct page*, get_block_t*); +int block_write_begin(struct file *, struct address_space *, + loff_t, unsigned, unsigned, + struct page **, void **, get_block_t*); +int block_write_end(struct file *, struct address_space *, + loff_t, unsigned, unsigned, + struct page *, void *); +int generic_write_end(struct file *, struct address_space *, + loff_t, unsigned, unsigned, + struct page *, void *); +void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*); int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*, loff_t *); diff --git a/include/linux/fs.h b/include/linux/fs.h index 86ce27c..e9344e6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -394,6 +394,8 @@ enum positive_aop_returns { AOP_TRUNCATED_PAGE = 0x80001, }; +#define AOP_FLAG_UNINTERRUPTIBLE 0x0001 /* will not do a short write */ + /* * oh the beauties of C type declarations. */ @@ -413,7 +415,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page, size_t iov_iter_copy_from_user(struct page *page, struct iov_iter *i, unsigned long offset, size_t bytes); void iov_iter_advance(struct iov_iter *i, size_t bytes); -int iov_iter_fault_in_readable(struct iov_iter *i); +int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes); size_t iov_iter_single_seg_count(struct iov_iter *i); static inline void iov_iter_init(struct iov_iter *i, @@ -454,6 +456,14 @@ struct address_space_operations { */ 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); + /* Unfortunately this kludge is needed for FIBMAP. Don't use it */ sector_t (*bmap)(struct address_space *, sector_t); void (*invalidatepage) (struct page *, unsigned long); @@ -468,6 +478,18 @@ struct address_space_operations { int (*launder_page) (struct page *); }; +/* + * pagecache_write_begin/pagecache_write_end must be used by general code + * to write into the pagecache. + */ +int pagecache_write_begin(struct file *, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata); + +int pagecache_write_end(struct file *, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata); + struct backing_dev_info; struct address_space { struct inode *host; /* owner: inode, block_device */ @@ -1866,6 +1888,12 @@ extern int simple_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to); extern int simple_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to); +extern int simple_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata); +extern int simple_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata); extern struct dentry *simple_lookup(struct inode *, struct dentry *, struct nameidata *); extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *); diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 8f1e390..db8a410 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -96,6 +96,8 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start, unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, int tag, unsigned int nr_pages, struct page **pages); +struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index); + /* * Returns locked page at given index in given cache, creating it if needed. */ diff --git a/mm/filemap.c b/mm/filemap.c index 67a03a0..ec25ba1 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1742,11 +1742,20 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes) i->count -= bytes; } -int iov_iter_fault_in_readable(struct iov_iter *i) +/* + * Fault in the first iovec of the given iov_iter, to a maximum length + * of bytes. Returns 0 on success, or non-zero if the memory could not be + * accessed (ie. because it is an invalid address). + * + * writev-intensive code may want this to prefault several iovecs -- that + * would be possible (callers must not rely on the fact that _only_ the + * first iovec will be faulted with the current implementation). + */ +int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) { - size_t seglen = min(i->iov->iov_len - i->iov_offset, i->count); char __user *buf = i->iov->iov_base + i->iov_offset; - return fault_in_pages_readable(buf, seglen); + bytes = min(bytes, i->iov->iov_len - i->iov_offset); + return fault_in_pages_readable(buf, bytes); } /* @@ -1843,6 +1852,95 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i } EXPORT_SYMBOL(generic_write_checks); +int pagecache_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + if (aops->write_begin) { + 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) { + if (ret != AOP_TRUNCATED_PAGE) + unlock_page(page); + page_cache_release(page); + if (pos + len > inode->i_size) + vmtruncate(inode, inode->i_size); + if (ret == AOP_TRUNCATED_PAGE) + goto again; + } + return ret; + } +} +EXPORT_SYMBOL(pagecache_write_begin); + +int pagecache_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + 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); + BUG_ON(ret == AOP_TRUNCATED_PAGE); /* can't deal with */ + + 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; +} +EXPORT_SYMBOL(pagecache_write_end); + ssize_t generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, unsigned long *nr_segs, loff_t pos, loff_t *ppos, @@ -1886,8 +1984,7 @@ EXPORT_SYMBOL(generic_file_direct_write); * Find or create a page at the given pagecache position. Return the locked * page. This function is specifically for buffered writes. */ -static struct page *__grab_cache_page(struct address_space *mapping, - pgoff_t index) +struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index) { int status; struct page *page; @@ -1908,20 +2005,16 @@ repeat: } return page; } +EXPORT_SYMBOL(__grab_cache_page); -ssize_t -generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, - unsigned long nr_segs, loff_t pos, loff_t *ppos, - size_t count, ssize_t written) +static ssize_t generic_perform_write_2copy(struct file *file, + struct iov_iter *i, loff_t pos) { - struct file *file = iocb->ki_filp; 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; - struct iov_iter i; - - iov_iter_init(&i, iov, nr_segs, count, written); + struct inode *inode = mapping->host; + long status = 0; + ssize_t written = 0; do { struct page *src_page; @@ -1934,7 +2027,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, offset = (pos & (PAGE_CACHE_SIZE - 1)); index = pos >> PAGE_CACHE_SHIFT; bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, - iov_iter_count(&i)); + iov_iter_count(i)); /* * a non-NULL src_page indicates that we're doing the @@ -1952,7 +2045,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * to check that the address is actually valid, when atomic * usercopies are used, below. */ - if (unlikely(iov_iter_fault_in_readable(&i))) { + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { status = -EFAULT; break; } @@ -1983,7 +2076,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * 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, + copied = iov_iter_copy_from_user(src_page, i, offset, bytes); if (unlikely(copied == 0)) { status = -EFAULT; @@ -2008,7 +2101,6 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, page_cache_release(src_page); continue; } - } status = a_ops->prepare_write(file, page, offset, offset+bytes); @@ -2030,7 +2122,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * really matter. */ pagefault_disable(); - copied = iov_iter_copy_from_user_atomic(page, &i, + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); } else { @@ -2056,9 +2148,9 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, if (src_page) page_cache_release(src_page); - iov_iter_advance(&i, copied); - written += copied; + iov_iter_advance(i, copied); pos += copied; + written += copied; balance_dirty_pages_ratelimited(mapping); cond_resched(); @@ -2082,13 +2174,117 @@ fs_write_aop_error: continue; else break; - } while (iov_iter_count(&i)); - *ppos = pos; + } 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) +{ + struct address_space *mapping = file->f_mapping; + const struct address_space_operations *a_ops = mapping->a_ops; + long status = 0; + ssize_t written = 0; + + do { + 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 */ + void *fsdata; + + offset = (pos & (PAGE_CACHE_SIZE - 1)); + index = pos >> PAGE_CACHE_SHIFT; + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_count(i)); + +again: + + /* + * 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; + } + + status = a_ops->write_begin(file, mapping, pos, bytes, 0, + &page, &fsdata); + if (unlikely(status)) + break; + + pagefault_disable(); + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); + pagefault_enable(); + flush_dcache_page(page); + + status = a_ops->write_end(file, mapping, pos, bytes, copied, + page, fsdata); + if (unlikely(status < 0)) + break; + copied = status; + + cond_resched(); + + if (unlikely(copied == 0)) { + /* + * If we were unable to copy any data at all, we must + * fall back to a single segment length write. + * + * If we didn't fallback here, we could livelock + * because not all segments in the iov can be copied at + * once without a pagefault. + */ + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_single_seg_count(i)); + goto again; + } + iov_iter_advance(i, copied); + pos += copied; + written += copied; + + balance_dirty_pages_ratelimited(mapping); + + } while (iov_iter_count(i)); + + return written ? written : status; +} + +ssize_t +generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, + unsigned long nr_segs, loff_t pos, loff_t *ppos, + size_t count, ssize_t written) +{ + struct file *file = iocb->ki_filp; + struct address_space *mapping = file->f_mapping; + const struct address_space_operations *a_ops = mapping->a_ops; + struct inode *inode = mapping->host; + ssize_t status; + 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); - /* - * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC - */ if (likely(status >= 0)) { + written += status; + *ppos = pos + status; + + /* + * For now, when the user asks for O_SYNC, we'll actually give + * O_DSYNC + */ if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { if (!a_ops->writepage || !is_sync_kiocb(iocb)) status = generic_osync_inode(inode, mapping, |
