fallocate should be a file operation

Currently all filesystems except XFS implement fallocate asynchronously,
while XFS forced a commit.  Both of these are suboptimal - in case of O_SYNC
I/O we really want our allocation on disk, especially for the !KEEP_SIZE
case where we actually grow the file with user-visible zeroes.  On the
other hand always commiting the transaction is a bad idea for fast-path
uses of fallocate like for example in recent Samba versions.   Given
that block allocation is a data plane operation anyway change it from
an inode operation to a file operation so that we have the file structure
available that lets us check for O_SYNC.

This also includes moving the code around for a few of the filesystems,
and remove the already unnedded S_ISDIR checks given that we only wire
up fallocate for regular files.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/Locking

@@ -60,7 +60,6 @@ ata *);
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
 	int (*removexattr) (struct dentry *, const char *);
 	void (*truncate_range)(struct inode *, loff_t, loff_t);
-	long (*fallocate)(struct inode *inode, int mode, loff_t offset, loff_t len);
 	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
 
 locking rules:
@@ -88,7 +87,6 @@ getxattr:	no
 listxattr:	no
 removexattr:	yes
 truncate_range:	yes
-fallocate:	no
 fiemap:		no
 	Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
 victim.
@@ -437,6 +435,7 @@ prototypes:
 	ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
 			size_t, unsigned int);
 	int (*setlease)(struct file *, long, struct file_lock **);
+	long (*fallocate)(struct file *, int, loff_t, loff_t);
 };
 
 locking rules:

fs/btrfs/file.c

@@ -24,6 +24,7 @@
 #include <linux/string.h>
 #include <linux/backing-dev.h>
 #include <linux/mpage.h>
+#include <linux/falloc.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
 #include <linux/statfs.h>
@@ -1237,6 +1238,117 @@ static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
 	return 0;
 }
 
+static long btrfs_fallocate(struct file *file, int mode,
+			    loff_t offset, loff_t len)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct extent_state *cached_state = NULL;
+	u64 cur_offset;
+	u64 last_byte;
+	u64 alloc_start;
+	u64 alloc_end;
+	u64 alloc_hint = 0;
+	u64 locked_end;
+	u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
+	struct extent_map *em;
+	int ret;
+
+	alloc_start = offset & ~mask;
+	alloc_end =  (offset + len + mask) & ~mask;
+
+	/* We only support the FALLOC_FL_KEEP_SIZE mode */
+	if (mode & ~FALLOC_FL_KEEP_SIZE)
+		return -EOPNOTSUPP;
+
+	/*
+	 * wait for ordered IO before we have any locks.  We'll loop again
+	 * below with the locks held.
+	 */
+	btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
+
+	mutex_lock(&inode->i_mutex);
+	ret = inode_newsize_ok(inode, alloc_end);
+	if (ret)
+		goto out;
+
+	if (alloc_start > inode->i_size) {
+		ret = btrfs_cont_expand(inode, alloc_start);
+		if (ret)
+			goto out;
+	}
+
+	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
+	if (ret)
+		goto out;
+
+	locked_end = alloc_end - 1;
+	while (1) {
+		struct btrfs_ordered_extent *ordered;
+
+		/* the extent lock is ordered inside the running
+		 * transaction
+		 */
+		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
+				 locked_end, 0, &cached_state, GFP_NOFS);
+		ordered = btrfs_lookup_first_ordered_extent(inode,
+							    alloc_end - 1);
+		if (ordered &&
+		    ordered->file_offset + ordered->len > alloc_start &&
+		    ordered->file_offset < alloc_end) {
+			btrfs_put_ordered_extent(ordered);
+			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+					     alloc_start, locked_end,
+					     &cached_state, GFP_NOFS);
+			/*
+			 * we can't wait on the range with the transaction
+			 * running or with the extent lock held
+			 */
+			btrfs_wait_ordered_range(inode, alloc_start,
+						 alloc_end - alloc_start);
+		} else {
+			if (ordered)
+				btrfs_put_ordered_extent(ordered);
+			break;
+		}
+	}
+
+	cur_offset = alloc_start;
+	while (1) {
+		em = btrfs_get_extent(inode, NULL, 0, cur_offset,
+				      alloc_end - cur_offset, 0);
+		BUG_ON(IS_ERR(em) || !em);
+		last_byte = min(extent_map_end(em), alloc_end);
+		last_byte = (last_byte + mask) & ~mask;
+		if (em->block_start == EXTENT_MAP_HOLE ||
+		    (cur_offset >= inode->i_size &&
+		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
+			ret = btrfs_prealloc_file_range(inode, mode, cur_offset,
+							last_byte - cur_offset,
+							1 << inode->i_blkbits,
+							offset + len,
+							&alloc_hint);
+			if (ret < 0) {
+				free_extent_map(em);
+				break;
+			}
+		}
+		free_extent_map(em);
+
+		cur_offset = last_byte;
+		if (cur_offset >= alloc_end) {
+			ret = 0;
+			break;
+		}
+	}
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
+			     &cached_state, GFP_NOFS);
+
+	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
+out:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
 const struct file_operations btrfs_file_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= do_sync_read,
@@ -1248,6 +1360,7 @@ const struct file_operations btrfs_file_operations = {
 	.open		= generic_file_open,
 	.release	= btrfs_release_file,
 	.fsync		= btrfs_sync_file,
+	.fallocate	= btrfs_fallocate,
 	.unlocked_ioctl	= btrfs_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= btrfs_ioctl,

fs/btrfs/inode.c

@@ -7098,116 +7098,6 @@ int btrfs_prealloc_file_range_trans(struct inode *inode,
 					   min_size, actual_len, alloc_hint, trans);
 }
 
-static long btrfs_fallocate(struct inode *inode, int mode,
-			    loff_t offset, loff_t len)
-{
-	struct extent_state *cached_state = NULL;
-	u64 cur_offset;
-	u64 last_byte;
-	u64 alloc_start;
-	u64 alloc_end;
-	u64 alloc_hint = 0;
-	u64 locked_end;
-	u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
-	struct extent_map *em;
-	int ret;
-
-	alloc_start = offset & ~mask;
-	alloc_end =  (offset + len + mask) & ~mask;
-
-	/* We only support the FALLOC_FL_KEEP_SIZE mode */
-	if (mode & ~FALLOC_FL_KEEP_SIZE)
-		return -EOPNOTSUPP;
-
-	/*
-	 * wait for ordered IO before we have any locks.  We'll loop again
-	 * below with the locks held.
-	 */
-	btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
-
-	mutex_lock(&inode->i_mutex);
-	ret = inode_newsize_ok(inode, alloc_end);
-	if (ret)
-		goto out;
-
-	if (alloc_start > inode->i_size) {
-		ret = btrfs_cont_expand(inode, alloc_start);
-		if (ret)
-			goto out;
-	}
-
-	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
-	if (ret)
-		goto out;
-
-	locked_end = alloc_end - 1;
-	while (1) {
-		struct btrfs_ordered_extent *ordered;
-
-		/* the extent lock is ordered inside the running
-		 * transaction
-		 */
-		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
-				 locked_end, 0, &cached_state, GFP_NOFS);
-		ordered = btrfs_lookup_first_ordered_extent(inode,
-							    alloc_end - 1);
-		if (ordered &&
-		    ordered->file_offset + ordered->len > alloc_start &&
-		    ordered->file_offset < alloc_end) {
-			btrfs_put_ordered_extent(ordered);
-			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
-					     alloc_start, locked_end,
-					     &cached_state, GFP_NOFS);
-			/*
-			 * we can't wait on the range with the transaction
-			 * running or with the extent lock held
-			 */
-			btrfs_wait_ordered_range(inode, alloc_start,
-						 alloc_end - alloc_start);
-		} else {
-			if (ordered)
-				btrfs_put_ordered_extent(ordered);
-			break;
-		}
-	}
-
-	cur_offset = alloc_start;
-	while (1) {
-		em = btrfs_get_extent(inode, NULL, 0, cur_offset,
-				      alloc_end - cur_offset, 0);
-		BUG_ON(IS_ERR(em) || !em);
-		last_byte = min(extent_map_end(em), alloc_end);
-		last_byte = (last_byte + mask) & ~mask;
-		if (em->block_start == EXTENT_MAP_HOLE ||
-		    (cur_offset >= inode->i_size &&
-		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
-			ret = btrfs_prealloc_file_range(inode, mode, cur_offset,
-							last_byte - cur_offset,
-							1 << inode->i_blkbits,
-							offset + len,
-							&alloc_hint);
-			if (ret < 0) {
-				free_extent_map(em);
-				break;
-			}
-		}
-		free_extent_map(em);
-
-		cur_offset = last_byte;
-		if (cur_offset >= alloc_end) {
-			ret = 0;
-			break;
-		}
-	}
-	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
-			     &cached_state, GFP_NOFS);
-
-	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
-out:
-	mutex_unlock(&inode->i_mutex);
-	return ret;
-}
-
 static int btrfs_set_page_dirty(struct page *page)
 {
 	return __set_page_dirty_nobuffers(page);
@@ -7310,7 +7200,6 @@ static const struct inode_operations btrfs_file_inode_operations = {
 	.listxattr      = btrfs_listxattr,
 	.removexattr	= btrfs_removexattr,
 	.permission	= btrfs_permission,
-	.fallocate	= btrfs_fallocate,
 	.fiemap		= btrfs_fiemap,
 };
 static const struct inode_operations btrfs_special_inode_operations = {

fs/ext4/ext4.h

@@ -2065,7 +2065,7 @@ extern int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 extern void ext4_ext_truncate(struct inode *);
 extern void ext4_ext_init(struct super_block *);
 extern void ext4_ext_release(struct super_block *);
-extern long ext4_fallocate(struct inode *inode, int mode, loff_t offset,
+extern long ext4_fallocate(struct file *file, int mode, loff_t offset,
 			  loff_t len);
 extern int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
 			  ssize_t len);

fs/ext4/extents.c

@@ -3627,14 +3627,15 @@ static void ext4_falloc_update_inode(struct inode *inode,
 }
 
 /*
- * preallocate space for a file. This implements ext4's fallocate inode
+ * preallocate space for a file. This implements ext4's fallocate file
  * operation, which gets called from sys_fallocate system call.
  * For block-mapped files, posix_fallocate should fall back to the method
  * of writing zeroes to the required new blocks (the same behavior which is
  * expected for file systems which do not support fallocate() system call).
  */
-long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
+long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 {
+	struct inode *inode = file->f_path.dentry->d_inode;
 	handle_t *handle;
 	loff_t new_size;
 	unsigned int max_blocks;
@@ -3655,10 +3656,6 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
 	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
 		return -EOPNOTSUPP;
 
-	/* preallocation to directories is currently not supported */
-	if (S_ISDIR(inode->i_mode))
-		return -ENODEV;
-
 	map.m_lblk = offset >> blkbits;
 	/*
 	 * We can't just convert len to max_blocks because

fs/ext4/file.c

@@ -210,6 +210,7 @@ const struct file_operations ext4_file_operations = {
 	.fsync		= ext4_sync_file,
 	.splice_read	= generic_file_splice_read,
 	.splice_write	= generic_file_splice_write,
+	.fallocate	= ext4_fallocate,
 };
 
 const struct inode_operations ext4_file_inode_operations = {
@@ -223,7 +224,6 @@ const struct inode_operations ext4_file_inode_operations = {
 	.removexattr	= generic_removexattr,
 #endif
 	.check_acl	= ext4_check_acl,
-	.fallocate	= ext4_fallocate,
 	.fiemap		= ext4_fiemap,
 };