diff options
Diffstat (limited to 'fs/afs/write.c')
| -rw-r--r-- | fs/afs/write.c | 835 |
1 files changed, 835 insertions, 0 deletions
diff --git a/fs/afs/write.c b/fs/afs/write.c new file mode 100644 index 000000000000..83ff29262816 --- /dev/null +++ b/fs/afs/write.c @@ -0,0 +1,835 @@ +/* handling of writes to regular files and writing back to the server + * + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/pagemap.h> +#include <linux/writeback.h> +#include <linux/pagevec.h> +#include "internal.h" + +static int afs_write_back_from_locked_page(struct afs_writeback *wb, + struct page *page); + +/* + * mark a page as having been made dirty and thus needing writeback + */ +int afs_set_page_dirty(struct page *page) +{ + _enter(""); + return __set_page_dirty_nobuffers(page); +} + +/* + * unlink a writeback record because its usage has reached zero + * - must be called with the wb->vnode->writeback_lock held + */ +static void afs_unlink_writeback(struct afs_writeback *wb) +{ + struct afs_writeback *front; + struct afs_vnode *vnode = wb->vnode; + + list_del_init(&wb->link); + if (!list_empty(&vnode->writebacks)) { + /* if an fsync rises to the front of the queue then wake it + * up */ + front = list_entry(vnode->writebacks.next, + struct afs_writeback, link); + if (front->state == AFS_WBACK_SYNCING) { + _debug("wake up sync"); + front->state = AFS_WBACK_COMPLETE; + wake_up(&front->waitq); + } + } +} + +/* + * free a writeback record + */ +static void afs_free_writeback(struct afs_writeback *wb) +{ + _enter(""); + key_put(wb->key); + kfree(wb); +} + +/* + * dispose of a reference to a writeback record + */ +void afs_put_writeback(struct afs_writeback *wb) +{ + struct afs_vnode *vnode = wb->vnode; + + _enter("{%d}", wb->usage); + + spin_lock(&vnode->writeback_lock); + if (--wb->usage == 0) + afs_unlink_writeback(wb); + else + wb = NULL; + spin_unlock(&vnode->writeback_lock); + if (wb) + afs_free_writeback(wb); +} + +/* + * partly or wholly fill a page that's under preparation for writing + */ +static int afs_fill_page(struct afs_vnode *vnode, struct key *key, + unsigned start, unsigned len, struct page *page) +{ + int ret; + + _enter(",,%u,%u", start, len); + + ASSERTCMP(start + len, <=, PAGE_SIZE); + + ret = afs_vnode_fetch_data(vnode, key, start, len, page); + if (ret < 0) { + if (ret == -ENOENT) { + _debug("got NOENT from server" + " - marking file deleted and stale"); + set_bit(AFS_VNODE_DELETED, &vnode->flags); + ret = -ESTALE; + } + } + + _leave(" = %d", ret); + return ret; +} + +/* + * prepare a page for being written to + */ +static int afs_prepare_page(struct afs_vnode *vnode, struct page *page, + struct key *key, unsigned offset, unsigned to) +{ + unsigned eof, tail, start, stop, len; + loff_t i_size, pos; + void *p; + int ret; + + _enter(""); + + if (offset == 0 && to == PAGE_SIZE) + return 0; + + p = kmap(page); + + i_size = i_size_read(&vnode->vfs_inode); + pos = (loff_t) page->index << PAGE_SHIFT; + if (pos >= i_size) { + /* partial write, page beyond EOF */ + _debug("beyond"); + if (offset > 0) + memset(p, 0, offset); + if (to < PAGE_SIZE) + memset(p + to, 0, PAGE_SIZE - to); + kunmap(page); + return 0; + } + + if (i_size - pos >= PAGE_SIZE) { + /* partial write, page entirely before EOF */ + _debug("before"); + tail = eof = PAGE_SIZE; + } else { + /* partial write, page overlaps EOF */ + eof = i_size - pos; + _debug("overlap %u", eof); + tail = max(eof, to); + if (tail < PAGE_SIZE) + memset(p + tail, 0, PAGE_SIZE - tail); + if (offset > eof) + memset(p + eof, 0, PAGE_SIZE - eof); + } + + kunmap(p); + + ret = 0; + if (offset > 0 || eof > to) { + /* need to fill one or two bits that aren't going to be written + * (cover both fillers in one read if there are two) */ + start = (offset > 0) ? 0 : to; + stop = (eof > to) ? eof : offset; + len = stop - start; + _debug("wr=%u-%u av=0-%u rd=%u@%u", + offset, to, eof, start, len); + ret = afs_fill_page(vnode, key, start, len, page); + } + + _leave(" = %d", ret); + return ret; +} + +/* + * prepare to perform part of a write to a page + * - the caller holds the page locked, preventing it from being written out or + * modified by anyone else + */ +int afs_prepare_write(struct file *file, struct page *page, + unsigned offset, unsigned to) +{ + struct afs_writeback *candidate, *wb; + struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode); + struct key *key = file->private_data; + pgoff_t index; + int ret; + + _enter("{%x:%u},{%lx},%u,%u", + vnode->fid.vid, vnode->fid.vnode, page->index, offset, to); + + candidate = kzalloc(sizeof(*candidate), GFP_KERNEL); + if (!candidate) + return -ENOMEM; + candidate->vnode = vnode; + candidate->first = candidate->last = page->index; + candidate->offset_first = offset; + candidate->to_last = to; + candidate->usage = 1; + candidate->state = AFS_WBACK_PENDING; + init_waitqueue_head(&candidate->waitq); + + if (!PageUptodate(page)) { + _debug("not up to date"); + ret = afs_prepare_page(vnode, page, key, offset, to); + if (ret < 0) { + kfree(candidate); + _leave(" = %d [prep]", ret); + return ret; + } + SetPageUptodate(page); + } + +try_again: + index = page->index; + spin_lock(&vnode->writeback_lock); + + /* see if this page is already pending a writeback under a suitable key + * - if so we can just join onto that one */ + wb = (struct afs_writeback *) page_private(page); + if (wb) { + if (wb->key == key && wb->state == AFS_WBACK_PENDING) + goto subsume_in_current_wb; + goto flush_conflicting_wb; + } + + if (index > 0) { + /* see if we can find an already pending writeback that we can + * append this page to */ + list_for_each_entry(wb, &vnode->writebacks, link) { + if (wb->last == index - 1 && wb->key == key && + wb->state == AFS_WBACK_PENDING) + goto append_to_previous_wb; + } + } + + list_add_tail(&candidate->link, &vnode->writebacks); + candidate->key = key_get(key); + spin_unlock(&vnode->writeback_lock); + SetPagePrivate(page); + set_page_private(page, (unsigned long) candidate); + _leave(" = 0 [new]"); + return 0; + +subsume_in_current_wb: + _debug("subsume"); + ASSERTRANGE(wb->first, <=, index, <=, wb->last); + if (index == wb->first && offset < wb->offset_first) + wb->offset_first = offset; + if (index == wb->last && to > wb->to_last) + wb->to_last = to; + spin_unlock(&vnode->writeback_lock); + kfree(candidate); + _leave(" = 0 [sub]"); + return 0; + +append_to_previous_wb: + _debug("append into %lx-%lx", wb->first, wb->last); + wb->usage++; + wb->last++; + wb->to_last = to; + spin_unlock(&vnode->writeback_lock); + SetPagePrivate(page); + set_page_private(page, (unsigned long) wb); + kfree(candidate); + _leave(" = 0 [app]"); + return 0; + + /* the page is currently bound to another context, so if it's dirty we + * need to flush it before we can use the new context */ +flush_conflicting_wb: + _debug("flush conflict"); + if (wb->state == AFS_WBACK_PENDING) + wb->state = AFS_WBACK_CONFLICTING; + spin_unlock(&vnode->writeback_lock); + if (PageDirty(page)) { + ret = afs_write_back_from_locked_page(wb, page); + if (ret < 0) { + afs_put_writeback(candidate); + _leave(" = %d", ret); + return ret; + } + } + + /* the page holds a ref on the writeback record */ + afs_put_writeback(wb); + set_page_private(page, 0); + ClearPagePrivate(page); + goto try_again; +} + +/* + * finalise part of a write to a page + */ +int afs_commit_write(struct file *file, struct page *page, + unsigned offset, unsigned to) +{ + struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode); + loff_t i_size, maybe_i_size; + + _enter("{%x:%u},{%lx},%u,%u", + vnode->fid.vid, vnode->fid.vnode, page->index, offset, to); + + maybe_i_size = (loff_t) page->index << PAGE_SHIFT; + maybe_i_size += to; + + i_size = i_size_read(&vnode->vfs_inode); + if (maybe_i_size > i_size) { + spin_lock(&vnode->writeback_lock); + i_size = i_size_read(&vnode->vfs_inode); + if (maybe_i_size > i_size) + i_size_write(&vnode->vfs_inode, maybe_i_size); + spin_unlock(&vnode->writeback_lock); + } + + set_page_dirty(page); + + if (PageDirty(page)) + _debug("dirtied"); + + return 0; +} + +/* + * kill all the pages in the given range + */ +static void afs_kill_pages(struct afs_vnode *vnode, bool error, + pgoff_t first, pgoff_t last) +{ + struct pagevec pv; + unsigned count, loop; + + _enter("{%x:%u},%lx-%lx", + vnode->fid.vid, vnode->fid.vnode, first, last); + + pagevec_init(&pv, 0); + + do { + _debug("kill %lx-%lx", first, last); + + count = last - first + 1; + if (count > PAGEVEC_SIZE) + count = PAGEVEC_SIZE; + pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping, + first, count, pv.pages); + ASSERTCMP(pv.nr, ==, count); + + for (loop = 0; loop < count; loop++) { + ClearPageUptodate(pv.pages[loop]); + if (error) + SetPageError(pv.pages[loop]); + end_page_writeback(pv.pages[loop]); + } + + __pagevec_release(&pv); + } while (first < last); + + _leave(""); +} + +/* + * synchronously write back the locked page and any subsequent non-locked dirty + * pages also covered by the same writeback record + */ +static int afs_write_back_from_locked_page(struct afs_writeback *wb, + struct page *primary_page) +{ + struct page *pages[8], *page; + unsigned long count; + unsigned n, offset, to; + pgoff_t start, first, last; + int loop, ret; + + _enter(",%lx", primary_page->index); + + count = 1; + if (!clear_page_dirty_for_io(primary_page)) + BUG(); + if (test_set_page_writeback(primary_page)) + BUG(); + + /* find all consecutive lockable dirty pages, stopping when we find a + * page that is not immediately lockable, is not dirty or is missing, + * or we reach the end of the range */ + start = primary_page->index; + if (start >= wb->last) + goto no_more; + start++; + do { + _debug("more %lx [%lx]", start, count); + n = wb->last - start + 1; + if (n > ARRAY_SIZE(pages)) + n = ARRAY_SIZE(pages); + n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping, + start, n, pages); + _debug("fgpc %u", n); + if (n == 0) + goto no_more; + if (pages[0]->index != start) { + for (n--; n >= 0; n--) + put_page(pages[n]); + goto no_more; + } + + for (loop = 0; loop < n; loop++) { + page = pages[loop]; + if (page->index > wb->last) + break; + if (TestSetPageLocked(page)) + break; + if (!PageDirty(page) || + page_private(page) != (unsigned long) wb) { + unlock_page(page); + break; + } + if (!clear_page_dirty_for_io(page)) + BUG(); + if (test_set_page_writeback(page)) + BUG(); + unlock_page(page); + put_page(page); + } + count += loop; + if (loop < n) { + for (; loop < n; loop++) + put_page(pages[loop]); + goto no_more; + } + + start += loop; + } while (start <= wb->last && count < 65536); + +no_more: + /* we now have a contiguous set of dirty pages, each with writeback set + * and the dirty mark cleared; the first page is locked and must remain + * so, all the rest are unlocked */ + first = primary_page->index; + last = first + count - 1; + + offset = (first == wb->first) ? wb->offset_first : 0; + to = (last == wb->last) ? wb->to_last : PAGE_SIZE; + + _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to); + + ret = afs_vnode_store_data(wb, first, last, offset, to); + if (ret < 0) { + switch (ret) { + case -EDQUOT: + case -ENOSPC: + set_bit(AS_ENOSPC, + &wb->vnode->vfs_inode.i_mapping->flags); + break; + case -EROFS: + case -EIO: + case -EREMOTEIO: + case -EFBIG: + case -ENOENT: + case -ENOMEDIUM: + case -ENXIO: + afs_kill_pages(wb->vnode, true, first, last); + set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags); + break; + case -EACCES: + case -EPERM: + case -ENOKEY: + case -EKEYEXPIRED: + case -EKEYREJECTED: + case -EKEYREVOKED: + afs_kill_pages(wb->vnode, false, first, last); + break; + default: + break; + } + } else { + ret = count; + } + + _leave(" = %d", ret); + return ret; +} + +/* + * write a page back to the server + * - the caller locked the page for us + */ +int afs_writepage(struct page *page, struct writeback_control *wbc) +{ + struct backing_dev_info *bdi = page->mapping->backing_dev_info; + struct afs_writeback *wb; + int ret; + + _enter("{%lx},", page->index); + + if (wbc->sync_mode != WB_SYNC_NONE) + wait_on_page_writeback(page); + + if (PageWriteback(page) || !PageDirty(page)) { + unlock_page(page); + return 0; + } + + wb = (struct afs_writeback *) page_private(page); + ASSERT(wb != NULL); + + ret = afs_write_back_from_locked_page(wb, page); + unlock_page(page); + if (ret < 0) { + _leave(" = %d", ret); + return 0; + } + + wbc->nr_to_write -= ret; + if (wbc->nonblocking && bdi_write_congested(bdi)) + wbc->encountered_congestion = 1; + + _leave(" = 0"); + return 0; +} + +/* + * write a region of pages back to the server + */ +int afs_writepages_region(struct address_space *mapping, + struct writeback_control *wbc, + pgoff_t index, pgoff_t end, pgoff_t *_next) +{ + struct backing_dev_info *bdi = mapping->backing_dev_info; + struct afs_writeback *wb; + struct page *page; + int ret, n; + + _enter(",,%lx,%lx,", index, end); + + do { + n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY, + 1, &page); + if (!n) + break; + + _debug("wback %lx", page->index); + + if (page->index > end) { + *_next = index; + page_cache_release(page); + _leave(" = 0 [%lx]", *_next); + return 0; + } + + /* at this point we hold neither mapping->tree_lock nor lock on + * the page itself: the page may be truncated or invalidated + * (changing page->mapping to NULL), or even swizzled back from + * swapper_space to tmpfs file mapping + */ + lock_page(page); + + if (page->mapping != mapping) { + unlock_page(page); + page_cache_release(page); + continue; + } + + if (wbc->sync_mode != WB_SYNC_NONE) + wait_on_page_writeback(page); + + if (PageWriteback(page) || !PageDirty(page)) { + unlock_page(page); + continue; + } + + wb = (struct afs_writeback *) page_private(page); + ASSERT(wb != NULL); + + spin_lock(&wb->vnode->writeback_lock); + wb->state = AFS_WBACK_WRITING; + spin_unlock(&wb->vnode->writeback_lock); + + ret = afs_write_back_from_locked_page(wb, page); + unlock_page(page); + page_cache_release(page); + if (ret < 0) { + _leave(" = %d", ret); + return ret; + } + + wbc->nr_to_write -= ret; + + if (wbc->nonblocking && bdi_write_congested(bdi)) { + wbc->encountered_congestion = 1; + break; + } + + cond_resched(); + } while (index < end && wbc->nr_to_write > 0); + + *_next = index; + _leave(" = 0 [%lx]", *_next); + return 0; +} + +/* + * write some of the pending data back to the server + */ +int afs_writepages(struct address_space *mapping, + struct writeback_control *wbc) +{ + struct backing_dev_info *bdi = mapping->backing_dev_info; + pgoff_t start, end, next; + int ret; + + _enter(""); + + if (wbc->nonblocking && bdi_write_congested(bdi)) { + wbc->encountered_congestion = 1; + _leave(" = 0 [congest]"); + return 0; + } + + if (wbc->range_cyclic) { + start = mapping->writeback_index; + end = -1; + ret = afs_writepages_region(mapping, wbc, start, end, &next); + if (start > 0 && wbc->nr_to_write > 0 && ret == 0 && + !(wbc->nonblocking && wbc->encountered_congestion)) + ret = afs_writepages_region(mapping, wbc, 0, start, + &next); + mapping->writeback_index = next; + } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) { + end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT); + ret = afs_writepages_region(mapping, wbc, 0, end, &next); + if (wbc->nr_to_write > 0) + mapping->writeback_index = next; + } else { + start = wbc->range_start >> PAGE_CACHE_SHIFT; + end = wbc->range_end >> PAGE_CACHE_SHIFT; + ret = afs_writepages_region(mapping, wbc, start, end, &next); + } + + _leave(" = %d", ret); + return ret; +} + +/* + * write an inode back + */ +int afs_write_inode(struct inode *inode, int sync) +{ + struct afs_vnode *vnode = AFS_FS_I(inode); + int ret; + + _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode); + + ret = 0; + if (sync) { + ret = filemap_fdatawait(inode->i_mapping); + if (ret < 0) + __mark_inode_dirty(inode, I_DIRTY_DATASYNC); + } + + _leave(" = %d", ret); + return ret; +} + +/* + * completion of write to server + */ +void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call) +{ + struct afs_writeback *wb = call->wb; + struct pagevec pv; + unsigned count, loop; + pgoff_t first = call->first, last = call->last; + bool free_wb; + + _enter("{%x:%u},{%lx-%lx}", + vnode->fid.vid, vnode->fid.vnode, first, last); + + ASSERT(wb != NULL); + + pagevec_init(&pv, 0); + + do { + _debug("attach %lx-%lx", first, last); + + count = last - first + 1; + if (count > PAGEVEC_SIZE) + count = PAGEVEC_SIZE; + pv.nr = find_get_pages_contig(call->mapping, first, count, + pv.pages); + ASSERTCMP(pv.nr, ==, count); + + spin_lock(&vnode->writeback_lock); + for (loop = 0; loop < count; loop++) { + struct page *page = pv.pages[loop]; + end_page_writeback(page); + if (page_private(page) == (unsigned long) wb) { + set_page_private(page, 0); + ClearPagePrivate(page); + wb->usage--; + } + } + free_wb = false; + if (wb->usage == 0) { + afs_unlink_writeback(wb); + free_wb = true; + } + spin_unlock(&vnode->writeback_lock); + first += count; + if (free_wb) { + afs_free_writeback(wb); + wb = NULL; + } + + __pagevec_release(&pv); + } while (first < last); + + _leave(""); +} + +/* + * write to an AFS file + */ +ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov, + unsigned long nr_segs, loff_t pos) +{ + struct dentry *dentry = iocb->ki_filp->f_path.dentry; + struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode); + ssize_t result; + size_t count = iov_length(iov, nr_segs); + int ret; + + _enter("{%x.%u},{%zu},%lu,", + vnode->fid.vid, vnode->fid.vnode, count, nr_segs); + + if (IS_SWAPFILE(&vnode->vfs_inode)) { + printk(KERN_INFO + "AFS: Attempt to write to active swap file!\n"); + return -EBUSY; + } + + if (!count) + return 0; + + result = generic_file_aio_write(iocb, iov, nr_segs, pos); + if (IS_ERR_VALUE(result)) { + _leave(" = %zd", result); + return result; + } + + /* return error values for O_SYNC and IS_SYNC() */ + if (IS_SYNC(&vnode->vfs_inode) || iocb->ki_filp->f_flags & O_SYNC) { + ret = afs_fsync(iocb->ki_filp, dentry, 1); + if (ret < 0) + result = ret; + } + + _leave(" = %zd", result); + return result; +} + +/* + * flush the vnode to the fileserver + */ +int afs_writeback_all(struct afs_vnode *vnode) +{ + struct address_space *mapping = vnode->vfs_inode.i_mapping; + struct writeback_control wbc = { + .bdi = mapping->backing_dev_info, + .sync_mode = WB_SYNC_ALL, + .nr_to_write = LONG_MAX, + .for_writepages = 1, + .range_cyclic = 1, + }; + int ret; + + _enter(""); + + ret = mapping->a_ops->writepages(mapping, &wbc); + __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); + + _leave(" = %d", ret); + return ret; +} + +/* + * flush any dirty pages for this process, and check for write errors. + * - the return status from this call provides a reliable indication of + * whether any write errors occurred for this process. + */ +int afs_fsync(struct file *file, struct dentry *dentry, int datasync) +{ + struct afs_writeback *wb, *xwb; + struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode); + int ret; + + _enter("{%x:%u},{n=%s},%d", + vnode->fid.vid, vnode->fid.vnode, dentry->d_name.name, + datasync); + + /* use a writeback record as a marker in the queue - when this reaches + * the front of the queue, all the outstanding writes are either + * completed or rejected */ + wb = kzalloc(sizeof(*wb), GFP_KERNEL); + if (!wb) + return -ENOMEM; + wb->vnode = vnode; + wb->first = 0; + wb->last = -1; + wb->offset_first = 0; + wb->to_last = PAGE_SIZE; + wb->usage = 1; + wb->state = AFS_WBACK_SYNCING; + init_waitqueue_head(&wb->waitq); + + spin_lock(&vnode->writeback_lock); + list_for_each_entry(xwb, &vnode->writebacks, link) { + if (xwb->state == AFS_WBACK_PENDING) + xwb->state = AFS_WBACK_CONFLICTING; + } + list_add_tail(&wb->link, &vnode->writebacks); + spin_unlock(&vnode->writeback_lock); + + /* push all the outstanding writebacks to the server */ + ret = afs_writeback_all(vnode); + if (ret < 0) { + afs_put_writeback(wb); + _leave(" = %d [wb]", ret); + return ret; + } + + /* wait for the preceding writes to actually complete */ + ret = wait_event_interruptible(wb->waitq, + wb->state == AFS_WBACK_COMPLETE || + vnode->writebacks.next == &wb->link); + afs_put_writeback(wb); + _leave(" = %d", ret); + return ret; +} |