Btrfs: patch queue: page_mkwrite
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e639cc9..def33ac9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -31,6 +31,7 @@
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
+#include <linux/bit_spinlock.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
@@ -561,7 +562,7 @@
goto out;
if (!PageUptodate(page)) {
- ret = mpage_readpage(page, btrfs_get_block);
+ ret = btrfs_readpage(NULL, page);
lock_page(page);
if (!PageUptodate(page)) {
ret = -EIO;
@@ -1257,8 +1258,10 @@
path = btrfs_alloc_path();
BUG_ON(!path);
if (create & BTRFS_GET_BLOCK_CREATE) {
- WARN_ON(1);
- /* this almost but not quite works */
+ /*
+ * danger!, this only works if the page is properly up
+ * to date somehow
+ */
trans = btrfs_start_transaction(root, 1);
if (!trans) {
err = -ENOMEM;
@@ -1353,7 +1356,6 @@
ins.objectid, ins.offset,
ins.offset);
BUG_ON(ret);
- SetPageChecked(result->b_page);
btrfs_map_bh_to_logical(root, result, ins.objectid);
}
out:
@@ -1374,6 +1376,40 @@
return err;
}
+int btrfs_get_block_csum(struct inode *inode, sector_t iblock,
+ struct buffer_head *result, int create)
+{
+ int ret;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct page *page = result->b_page;
+ u64 offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(result);
+ struct btrfs_csum_item *item;
+ struct btrfs_path *path = NULL;
+
+ mutex_lock(&root->fs_info->fs_mutex);
+ ret = btrfs_get_block_lock(inode, iblock, result, create);
+ if (ret)
+ goto out;
+
+ path = btrfs_alloc_path();
+ item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, offset, 0);
+ if (IS_ERR(item)) {
+ ret = PTR_ERR(item);
+ /* a csum that isn't present is a preallocated region. */
+ if (ret == -ENOENT || ret == -EFBIG)
+ ret = 0;
+ result->b_private = 0;
+ goto out;
+ }
+ memcpy((char *)&result->b_private, &item->csum, BTRFS_CRC32_SIZE);
+printk("get_block_sum file %lu offset %llu csum %X\n", inode->i_ino, (unsigned long long)offset, *(int *)(&item->csum));
+out:
+ if (path)
+ btrfs_free_path(path);
+ mutex_unlock(&root->fs_info->fs_mutex);
+ return ret;
+}
+
static int btrfs_get_block_bmap(struct inode *inode, sector_t iblock,
struct buffer_head *result, int create)
{
@@ -1395,9 +1431,198 @@
return block_prepare_write(page, from, to, btrfs_get_block);
}
-static int btrfs_readpage(struct file *file, struct page *page)
+static void buffer_io_error(struct buffer_head *bh)
{
- return mpage_readpage(page, btrfs_get_block);
+ char b[BDEVNAME_SIZE];
+
+ printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
+ bdevname(bh->b_bdev, b),
+ (unsigned long long)bh->b_blocknr);
+}
+
+/*
+ * I/O completion handler for block_read_full_page() - pages
+ * which come unlocked at the end of I/O.
+ */
+static void btrfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
+{
+ unsigned long flags;
+ struct buffer_head *first;
+ struct buffer_head *tmp;
+ struct page *page;
+ int page_uptodate = 1;
+ struct inode *inode;
+ int ret;
+
+ BUG_ON(!buffer_async_read(bh));
+
+ page = bh->b_page;
+ inode = page->mapping->host;
+ if (uptodate) {
+ void *kaddr;
+ struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+ if (bh->b_private) {
+ char csum[BTRFS_CRC32_SIZE];
+ kaddr = kmap_atomic(page, KM_IRQ0);
+ ret = btrfs_csum_data(root, kaddr + bh_offset(bh),
+ bh->b_size, csum);
+ BUG_ON(ret);
+ if (memcmp(csum, &bh->b_private, BTRFS_CRC32_SIZE)) {
+ u64 offset;
+ offset = (page->index << PAGE_CACHE_SHIFT) +
+ bh_offset(bh);
+ printk("btrfs csum failed ino %lu off %llu\n",
+ page->mapping->host->i_ino,
+ (unsigned long long)offset);
+ memset(kaddr + bh_offset(bh), 1, bh->b_size);
+ flush_dcache_page(page);
+printk("bad verify file %lu offset %llu bh_private %lX csum %X\n", inode->i_ino, (unsigned long long)offset, (unsigned long)(bh->b_private), *(int *)csum);
+ }
+ kunmap_atomic(kaddr, KM_IRQ0);
+ }
+ set_buffer_uptodate(bh);
+ } else {
+ clear_buffer_uptodate(bh);
+ if (printk_ratelimit())
+ buffer_io_error(bh);
+ SetPageError(page);
+ }
+
+ /*
+ * Be _very_ careful from here on. Bad things can happen if
+ * two buffer heads end IO at almost the same time and both
+ * decide that the page is now completely done.
+ */
+ first = page_buffers(page);
+ local_irq_save(flags);
+ bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ clear_buffer_async_read(bh);
+ unlock_buffer(bh);
+ tmp = bh;
+ do {
+ if (!buffer_uptodate(tmp))
+ page_uptodate = 0;
+ if (buffer_async_read(tmp)) {
+ BUG_ON(!buffer_locked(tmp));
+ goto still_busy;
+ }
+ tmp = tmp->b_this_page;
+ } while (tmp != bh);
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
+
+ /*
+ * If none of the buffers had errors and they are all
+ * uptodate then we can set the page uptodate.
+ */
+ if (page_uptodate && !PageError(page))
+ SetPageUptodate(page);
+ unlock_page(page);
+ return;
+
+still_busy:
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
+ return;
+}
+
+/*
+ * 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
+ * set/clear_buffer_uptodate() functions propagate buffer state into the
+ * page struct once IO has completed.
+ */
+int btrfs_readpage(struct file *file, struct page *page)
+{
+ struct inode *inode = page->mapping->host;
+ sector_t iblock, lblock;
+ struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
+ unsigned int blocksize;
+ int nr, i;
+ int fully_mapped = 1;
+
+ BUG_ON(!PageLocked(page));
+ blocksize = 1 << inode->i_blkbits;
+ if (!page_has_buffers(page))
+ create_empty_buffers(page, blocksize, 0);
+ head = page_buffers(page);
+
+ iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+ lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
+ bh = head;
+ nr = 0;
+ i = 0;
+
+ do {
+ if (buffer_uptodate(bh))
+ continue;
+
+ if (!buffer_mapped(bh)) {
+ int err = 0;
+
+ fully_mapped = 0;
+ if (iblock < lblock) {
+ WARN_ON(bh->b_size != blocksize);
+ err = btrfs_get_block_csum(inode, iblock,
+ bh, 0);
+ if (err)
+ SetPageError(page);
+ }
+ if (!buffer_mapped(bh)) {
+ void *kaddr = kmap_atomic(page, KM_USER0);
+ memset(kaddr + i * blocksize, 0, blocksize);
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_USER0);
+ if (!err)
+ set_buffer_uptodate(bh);
+ continue;
+ }
+ /*
+ * get_block() might have updated the buffer
+ * synchronously
+ */
+ if (buffer_uptodate(bh))
+ continue;
+ }
+ arr[nr++] = bh;
+ } while (i++, iblock++, (bh = bh->b_this_page) != head);
+
+ if (fully_mapped)
+ SetPageMappedToDisk(page);
+
+ if (!nr) {
+ /*
+ * All buffers are uptodate - we can set the page uptodate
+ * as well. But not if get_block() returned an error.
+ */
+ if (!PageError(page))
+ SetPageUptodate(page);
+ unlock_page(page);
+ return 0;
+ }
+
+ /* Stage two: lock the buffers */
+ for (i = 0; i < nr; i++) {
+ bh = arr[i];
+ lock_buffer(bh);
+ bh->b_end_io = btrfs_end_buffer_async_read;
+ set_buffer_async_read(bh);
+ }
+
+ /*
+ * Stage 3: start the IO. Check for uptodateness
+ * inside the buffer lock in case another process reading
+ * the underlying blockdev brought it uptodate (the sct fix).
+ */
+ for (i = 0; i < nr; i++) {
+ bh = arr[i];
+ if (buffer_uptodate(bh))
+ btrfs_end_buffer_async_read(bh, 1);
+ else
+ submit_bh(READ, bh);
+ }
+ return 0;
}
/*
@@ -1424,6 +1649,7 @@
struct buffer_head *bh, *head;
const unsigned blocksize = 1 << inode->i_blkbits;
int nr_underway = 0;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
BUG_ON(!PageLocked(page));
@@ -1496,6 +1722,24 @@
continue;
}
if (test_clear_buffer_dirty(bh) && bh->b_blocknr != 0) {
+ struct btrfs_trans_handle *trans;
+ int ret;
+ u64 off = page->index << PAGE_CACHE_SHIFT;
+ char *kaddr;
+
+ off += bh_offset(bh);
+ mutex_lock(&root->fs_info->fs_mutex);
+ trans = btrfs_start_transaction(root, 1);
+ btrfs_set_trans_block_group(trans, inode);
+ kaddr = kmap(page);
+ ret = btrfs_csum_file_block(trans, root, inode->i_ino,
+ off, kaddr + bh_offset(bh),
+ bh->b_size);
+ kunmap(page);
+ BUG_ON(ret);
+ ret = btrfs_end_transaction(trans, root);
+ BUG_ON(ret);
+ mutex_unlock(&root->fs_info->fs_mutex);
mark_buffer_async_write(bh);
} else {
unlock_buffer(bh);
@@ -1617,6 +1861,53 @@
return __btrfs_write_full_page(inode, page, wbc);
}
+/*
+ * btrfs_page_mkwrite() is not allowed to change the file size as it gets
+ * called from a page fault handler when a page is first dirtied. Hence we must
+ * be careful to check for EOF conditions here. We set the page up correctly
+ * for a written page which means we get ENOSPC checking when writing into
+ * holes and correct delalloc and unwritten extent mapping on filesystems that
+ * support these features.
+ *
+ * We are not allowed to take the i_mutex here so we have to play games to
+ * protect against truncate races as the page could now be beyond EOF. Because
+ * vmtruncate() writes the inode size before removing pages, once we have the
+ * page lock we can determine safely if the page is beyond EOF. If it is not
+ * beyond EOF, then the page is guaranteed safe against truncation until we
+ * unlock the page.
+ */
+int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+{
+ struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+ unsigned long end;
+ loff_t size;
+ int ret = -EINVAL;
+
+ lock_page(page);
+ wait_on_page_writeback(page);
+printk("btrfs_page_mkwrite %lu %lu\n", page->mapping->host->i_ino, page->index);
+ size = i_size_read(inode);
+ if ((page->mapping != inode->i_mapping) ||
+ ((page->index << PAGE_CACHE_SHIFT) > size)) {
+ /* page got truncated out from underneath us */
+ goto out_unlock;
+ }
+
+ /* page is wholly or partially inside EOF */
+ if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
+ end = size & ~PAGE_CACHE_MASK;
+ else
+ end = PAGE_CACHE_SIZE;
+
+ ret = btrfs_prepare_write(NULL, page, 0, end);
+ if (!ret)
+ ret = btrfs_commit_write(NULL, page, 0, end);
+
+out_unlock:
+ unlock_page(page);
+ return ret;
+}
+
static void btrfs_truncate(struct inode *inode)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
