btrfs_file_write -- first pass

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 213 insertions, 9 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 151c1002d74e..7914b31f5bcd 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -9,6 +9,8 @@
 #include <linux/smp_lock.h>
 #include <linux/backing-dev.h>
 #include <linux/mpage.h>
+#include <linux/swap.h>
+#include <linux/writeback.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -755,7 +757,7 @@ printk("btrfs sync_fs\n");
         return 0;
 }
 
-static int btrfs_get_block(struct inode *inode, sector_t iblock,
+static int btrfs_get_block_lock(struct inode *inode, sector_t iblock,
                            struct buffer_head *result, int create)
 {
         int ret;
@@ -772,7 +774,6 @@ static int btrfs_get_block(struct inode *inode, sector_t iblock,
         struct btrfs_disk_key *found_key;
 
         btrfs_init_path(&path);
-        mutex_lock(&root->fs_info->fs_mutex);
         if (create)
                 trans = btrfs_start_transaction(root, 1);
 
@@ -848,6 +849,16 @@ allocate:
 out:
         if (trans)
                 btrfs_end_transaction(trans, root);
+        return err;
+}
+
+static int btrfs_get_block(struct inode *inode, sector_t iblock,
+                           struct buffer_head *result, int create)
+{
+        int err;
+        struct btrfs_root *root = btrfs_sb(inode->i_sb);
+        mutex_lock(&root->fs_info->fs_mutex);
+        err = btrfs_get_block_lock(inode, iblock, result, create);
         mutex_unlock(&root->fs_info->fs_mutex);
         return err;
 }
@@ -855,8 +866,15 @@ out:
 static int btrfs_prepare_write(struct file *file, struct page *page,
                                unsigned from, unsigned to)
 {
+        WARN_ON(1);
         return nobh_prepare_write(page, from, to, btrfs_get_block);
 }
+static int btrfs_commit_write(struct file *file, struct page *page,
+                               unsigned from, unsigned to)
+{
+        WARN_ON(1);
+        return nobh_commit_write(file, page, from, to);
+}
 
 static void btrfs_write_super(struct super_block *sb)
 {
@@ -903,6 +921,196 @@ static void btrfs_truncate(struct inode *inode)
         mark_inode_dirty(inode);
 }
 
+static int btrfs_copy_from_user(loff_t pos, int num_pages, int write_bytes,
+                                struct page **prepared_pages,
+                                const char __user * buf)
+{
+        long page_fault = 0;
+        int i;
+        int offset = pos & (PAGE_CACHE_SIZE - 1);
+
+        for (i = 0; i < num_pages && write_bytes > 0; i++, offset = 0) {
+                size_t count = min_t(size_t,
+                                     PAGE_CACHE_SIZE - offset, write_bytes);
+                struct page *page = prepared_pages[i];
+                fault_in_pages_readable(buf, count);
+
+                /* Copy data from userspace to the current page */
+                kmap(page);
+                page_fault = __copy_from_user(page_address(page) + offset,
+                                              buf, count);
+                /* Flush processor's dcache for this page */
+                flush_dcache_page(page);
+                kunmap(page);
+                buf += count;
+                write_bytes -= count;
+
+                if (page_fault)
+                        break;
+        }
+        return page_fault ? -EFAULT : 0;
+}
+
+static void btrfs_drop_pages(struct page **pages, size_t num_pages)
+{
+        size_t i;
+        for (i = 0; i < num_pages; i++) {
+                if (!pages[i])
+                        break;
+                unlock_page(pages[i]);
+                mark_page_accessed(pages[i]);
+                page_cache_release(pages[i]);
+        }
+}
+static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
+                                   struct btrfs_root *root,
+                                   struct file *file,
+                                   struct page **pages,
+                                   size_t num_pages,
+                                   loff_t pos,
+                                   size_t write_bytes)
+{
+        int i;
+        int offset;
+        int err = 0;
+        int ret;
+        int this_write;
+
+        for (i = 0; i < num_pages; i++) {
+                offset = pos & (PAGE_CACHE_SIZE -1);
+                this_write = min(PAGE_CACHE_SIZE - offset, write_bytes);
+                ret = nobh_commit_write(file, pages[i], offset,
+                                         offset + this_write);
+                pos += this_write;
+                if (ret) {
+                        err = ret;
+                        goto failed;
+                }
+                WARN_ON(this_write > write_bytes);
+                write_bytes -= this_write;
+        }
+failed:
+        return err;
+}
+
+static int prepare_pages(struct btrfs_trans_handle *trans,
+                         struct btrfs_root *root,
+                         struct file *file,
+                         struct page **pages,
+                         size_t num_pages,
+                         loff_t pos,
+                         size_t write_bytes)
+{
+        int i;
+        unsigned long index = pos >> PAGE_CACHE_SHIFT;
+        struct inode *inode = file->f_path.dentry->d_inode;
+        int offset;
+        int err = 0;
+        int ret;
+        int this_write;
+        loff_t isize = i_size_read(inode);
+
+        memset(pages, 0, num_pages * sizeof(struct page *));
+
+        for (i = 0; i < num_pages; i++) {
+                pages[i] = grab_cache_page(inode->i_mapping, index + i);
+                if (!pages[i]) {
+                        err = -ENOMEM;
+                        goto failed_release;
+                }
+                offset = pos & (PAGE_CACHE_SIZE -1);
+                this_write = min(PAGE_CACHE_SIZE - offset, write_bytes);
+                ret = nobh_prepare_write(pages[i], offset,
+                                         offset + this_write,
+                                         btrfs_get_block_lock);
+                pos += this_write;
+                if (ret) {
+                        err = ret;
+                        goto failed_truncate;
+                }
+                WARN_ON(this_write > write_bytes);
+                write_bytes -= this_write;
+        }
+        return 0;
+
+failed_release:
+        btrfs_drop_pages(pages, num_pages);
+        return err;
+
+failed_truncate:
+        btrfs_drop_pages(pages, num_pages);
+        if (pos > isize)
+                vmtruncate(inode, isize);
+        return err;
+}
+
+static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        loff_t pos;
+        size_t num_written = 0;
+        int err = 0;
+        int ret = 0;
+        struct btrfs_trans_handle *trans;
+        struct inode *inode = file->f_path.dentry->d_inode;
+        struct btrfs_root *root = btrfs_sb(inode->i_sb);
+        struct page *pages[1];
+
+        if (file->f_flags & O_DIRECT)
+                return -EINVAL;
+        pos = *ppos;
+
+        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+        current->backing_dev_info = inode->i_mapping->backing_dev_info;
+        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
+        if (err)
+                goto out;
+        if (count == 0)
+                goto out;
+        err = remove_suid(file->f_path.dentry);
+        if (err)
+                goto out;
+        file_update_time(file);
+        mutex_lock(&inode->i_mutex);
+        while(count > 0) {
+                size_t offset = pos & (PAGE_CACHE_SIZE - 1);
+                size_t write_bytes = min(count, PAGE_CACHE_SIZE - offset);
+                size_t num_pages = (write_bytes + PAGE_CACHE_SIZE - 1) >>
+                                        PAGE_CACHE_SHIFT;
+                mutex_lock(&root->fs_info->fs_mutex);
+                trans = btrfs_start_transaction(root, 1);
+
+                ret = prepare_pages(trans, root, file, pages, num_pages,
+                                    pos, write_bytes);
+                BUG_ON(ret);
+                ret = btrfs_copy_from_user(pos, num_pages,
+                                           write_bytes, pages, buf);
+                BUG_ON(ret);
+
+                mutex_unlock(&root->fs_info->fs_mutex);
+
+                ret = dirty_and_release_pages(trans, root, file, pages,
+                                              num_pages, pos, write_bytes);
+                BUG_ON(ret);
+                btrfs_drop_pages(pages, num_pages);
+
+                ret = btrfs_end_transaction(trans, root);
+
+                buf += write_bytes;
+                count -= write_bytes;
+                pos += write_bytes;
+                num_written += write_bytes;
+
+                balance_dirty_pages_ratelimited(inode->i_mapping);
+                cond_resched();
+        }
+        mutex_unlock(&inode->i_mutex);
+out:
+        *ppos = pos;
+        current->backing_dev_info = NULL;
+        return num_written ? num_written : err;
+}
+
 static int btrfs_get_sb(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
@@ -948,7 +1156,7 @@ static struct address_space_operations btrfs_aops = {
         .writepage      = btrfs_writepage,
         .sync_page      = block_sync_page,
         .prepare_write  = btrfs_prepare_write,
-        .commit_write   = nobh_commit_write,
+        .commit_write   = btrfs_commit_write,
 };
 
 static struct inode_operations btrfs_file_inode_operations = {
@@ -958,14 +1166,10 @@ static struct inode_operations btrfs_file_inode_operations = {
 static struct file_operations btrfs_file_operations = {
         .llseek         = generic_file_llseek,
         .read           = do_sync_read,
-        .write          = do_sync_write,
-        .aio_read       = generic_file_aio_read,
-        .aio_write      = generic_file_aio_write,
+        .aio_read       = generic_file_aio_read,
+        .write          = btrfs_file_write,
         .mmap           = generic_file_mmap,
         .open           = generic_file_open,
-        .sendfile       = generic_file_sendfile,
-        .splice_read    = generic_file_splice_read,
-        .splice_write   = generic_file_splice_write,
 };
 
 static int __init init_btrfs_fs(void)