Re: [rfc][patch 4/4] fs: tmpfs, ext2 use new truncate

From: Nick Piggin
Date: Wed Jul 08 2009 - 08:39:24 EST

On Wed, Jul 08, 2009 at 08:32:44AM -0400, Christoph Hellwig wrote:
> On Wed, Jul 08, 2009 at 02:22:50PM +0200, Nick Piggin wrote:
> > OK fair enough. But I don't know if all those checks are
> > realy appropriate. For example an IS_APPEND inode should
> > be able to have its blocks trimmed off if a write fails.
>
> It should. But I think that's a separate issue of what we're trying to
> fix right now. So let's just do the method reshuffle now and then sort
> out the checks later.

Here is patch 4/4 after your parts folded in and other changes
I said in last mail. (yes I do agree to split it up, but I'll
just wait until we all agree on basics and then resend a new
patchset).

--
Convert ext2 and tmpfs to use the new truncate convention.

Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
fs/ext2/ext2.h | 1
fs/ext2/file.c | 2
fs/ext2/inode.c | 137 +++++++++++++++++++++++++++++++++++++++++++++-----------
mm/shmem.c | 35 +++++++-------
4 files changed, 131 insertions(+), 44 deletions(-)

Index: linux-2.6/fs/ext2/inode.c
===================================================================
--- linux-2.6.orig/fs/ext2/inode.c
+++ linux-2.6/fs/ext2/inode.c
@@ -53,6 +53,8 @@ static inline int ext2_inode_is_fast_sym
inode->i_blocks - ea_blocks == 0);
}

+static void ext2_truncate_blocks(struct inode *inode, loff_t offset);
+
/*
* Called at the last iput() if i_nlink is zero.
*/
@@ -68,7 +70,7 @@ void ext2_delete_inode (struct inode * i

inode->i_size = 0;
if (inode->i_blocks)
- ext2_truncate (inode);
+ ext2_truncate_blocks(inode, 0);
ext2_free_inode (inode);

return;
@@ -761,8 +763,33 @@ ext2_write_begin(struct file *file, stru
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
+ int ret;
+
*pagep = NULL;
- return __ext2_write_begin(file, mapping, pos, len, flags, pagep,fsdata);
+ ret = __ext2_write_begin(file, mapping, pos, len, flags, pagep,fsdata);
+ if (ret < 0) {
+ struct inode *inode = mapping->host;
+ loff_t isize = inode->i_size;
+ if (pos + len > isize)
+ ext2_truncate_blocks(inode, isize);
+ }
+ return ret;
+}
+
+static int ext2_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ int ret;
+
+ ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
+ if (ret < len) {
+ struct inode *inode = mapping->host;
+ loff_t isize = inode->i_size;
+ if (pos + len > isize)
+ ext2_truncate_blocks(inode, isize);
+ }
+ return ret;
}

static int
@@ -770,13 +797,22 @@ ext2_nobh_write_begin(struct file *file,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
+ int ret;
+
/*
* Dir-in-pagecache still uses ext2_write_begin. Would have to rework
* directory handling code to pass around offsets rather than struct
* pages in order to make this work easily.
*/
- return nobh_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
+ ret = nobh_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
ext2_get_block);
+ if (ret < 0) {
+ struct inode *inode = mapping->host;
+ loff_t isize = inode->i_size;
+ if (pos + len > isize)
+ ext2_truncate_blocks(inode, isize);
+ }
+ return ret;
}

static int ext2_nobh_writepage(struct page *page,
@@ -796,9 +832,15 @@ ext2_direct_IO(int rw, struct kiocb *ioc
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
+ ssize_t ret;

- return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
+ ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
offset, nr_segs, ext2_get_block, NULL);
+ if (ret < 0 && (rw & WRITE)) {
+ loff_t isize = inode->i_size;
+ ext2_truncate_blocks(inode, isize);
+ }
+ return ret;
}

static int
@@ -813,7 +855,7 @@ const struct address_space_operations ex
.writepage = ext2_writepage,
.sync_page = block_sync_page,
.write_begin = ext2_write_begin,
- .write_end = generic_write_end,
+ .write_end = ext2_write_end,
.bmap = ext2_bmap,
.direct_IO = ext2_direct_IO,
.writepages = ext2_writepages,
@@ -1020,7 +1062,7 @@ static void ext2_free_branches(struct in
ext2_free_data(inode, p, q);
}

-void ext2_truncate(struct inode *inode)
+static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
{
__le32 *i_data = EXT2_I(inode)->i_data;
struct ext2_inode_info *ei = EXT2_I(inode);
@@ -1032,27 +1074,8 @@ void ext2_truncate(struct inode *inode)
int n;
long iblock;
unsigned blocksize;
-
- if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
- S_ISLNK(inode->i_mode)))
- return;
- if (ext2_inode_is_fast_symlink(inode))
- return;
- if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
- return;
-
blocksize = inode->i_sb->s_blocksize;
- iblock = (inode->i_size + blocksize-1)
- >> EXT2_BLOCK_SIZE_BITS(inode->i_sb);
-
- if (mapping_is_xip(inode->i_mapping))
- xip_truncate_page(inode->i_mapping, inode->i_size);
- else if (test_opt(inode->i_sb, NOBH))
- nobh_truncate_page(inode->i_mapping,
- inode->i_size, ext2_get_block);
- else
- block_truncate_page(inode->i_mapping,
- inode->i_size, ext2_get_block);
+ iblock = (offset + blocksize-1) >> EXT2_BLOCK_SIZE_BITS(inode->i_sb);

n = ext2_block_to_path(inode, iblock, offsets, NULL);
if (n == 0)
@@ -1120,6 +1143,59 @@ do_indirects:
ext2_discard_reservation(inode);

mutex_unlock(&ei->truncate_mutex);
+}
+
+static void ext2_truncate_blocks(struct inode *inode, loff_t offset)
+{
+ /*
+ * XXX: it seems like a bug here that we don't allow
+ * IS_APPEND inode to have blocks-past-i_size trimmed off.
+ * review and fix this.
+ */
+ if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+ S_ISLNK(inode->i_mode)))
+ return -EINVAL;
+ if (ext2_inode_is_fast_symlink(inode))
+ return -EINVAL;
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+ return -EPERM;
+ __ext2_truncate_blocks(inode, offset);
+}
+
+int ext2_setsize(struct inode *inode, loff_t newsize)
+{
+ loff_t oldsize;
+ int error;
+
+ error = inode_newsize_ok(inode, newsize);
+ if (error)
+ return error;
+
+ if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+ S_ISLNK(inode->i_mode)))
+ return -EINVAL;
+ if (ext2_inode_is_fast_symlink(inode))
+ return -EINVAL;
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+ return -EPERM;
+
+ if (mapping_is_xip(inode->i_mapping))
+ error = xip_truncate_page(inode->i_mapping, newsize);
+ else if (test_opt(inode->i_sb, NOBH))
+ error = nobh_truncate_page(inode->i_mapping,
+ newsize, ext2_get_block);
+ else
+ error = block_truncate_page(inode->i_mapping,
+ newsize, ext2_get_block);
+ if (error)
+ return error;
+
+ oldsize = inode->i_size;
+ i_size_write(inode, newsize);
+ truncate_pagecache(inode, oldsize, newsize);
+
+ __ext2_truncate_blocks(inode, newsize);
+
inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
if (inode_needs_sync(inode)) {
sync_mapping_buffers(inode->i_mapping);
@@ -1127,6 +1203,8 @@ do_indirects:
} else {
mark_inode_dirty(inode);
}
+
+ return 0;
}

static struct ext2_inode *ext2_get_inode(struct super_block *sb, ino_t ino,
@@ -1459,6 +1537,13 @@ int ext2_setattr(struct dentry *dentry,
if (error)
return error;
}
+ if (iattr->ia_valid & ATTR_SIZE) {
+ error = ext2_setsize(inode, iattr->ia_size);
+ if (error)
+ return error;
+ iattr->ia_valid &= ~ATTR_SIZE;
+ /* strip ATTR_SIZE for inode_setattr */
+ }
error = inode_setattr(inode, iattr);
if (!error && (iattr->ia_valid & ATTR_MODE))
error = ext2_acl_chmod(inode);
Index: linux-2.6/mm/shmem.c
===================================================================
--- linux-2.6.orig/mm/shmem.c
+++ linux-2.6/mm/shmem.c
@@ -730,10 +730,11 @@ done2:
if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
/*
* Call truncate_inode_pages again: racing shmem_unuse_inode
- * may have swizzled a page in from swap since vmtruncate or
- * generic_delete_inode did it, before we lowered next_index.
- * Also, though shmem_getpage checks i_size before adding to
- * cache, no recheck after: so fix the narrow window there too.
+ * may have swizzled a page in from swap since
+ * truncate_pagecache or generic_delete_inode did it, before we
+ * lowered next_index. Also, though shmem_getpage checks
+ * i_size before adding to cache, no recheck after: so fix the
+ * narrow window there too.
*
* Recalling truncate_inode_pages_range and unmap_mapping_range
* every time for punch_hole (which never got a chance to clear
@@ -763,11 +764,6 @@ done2:
}
}

-static void shmem_truncate(struct inode *inode)
-{
- shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
-}
-
static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
@@ -775,6 +771,8 @@ static int shmem_notify_change(struct de
int error;

if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
+ loff_t newsize = attr->ia_size;
+
if (attr->ia_size < inode->i_size) {
/*
* If truncating down to a partial page, then
@@ -783,9 +781,9 @@ static int shmem_notify_change(struct de
* truncate_partial_page cannnot miss it were
* it assigned to swap.
*/
- if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
+ if (newsize & (PAGE_CACHE_SIZE-1)) {
(void) shmem_getpage(inode,
- attr->ia_size>>PAGE_CACHE_SHIFT,
+ newsize >> PAGE_CACHE_SHIFT,
&page, SGP_READ, NULL);
if (page)
unlock_page(page);
@@ -797,13 +795,19 @@ static int shmem_notify_change(struct de
* if it's being fully truncated to zero-length: the
* nrpages check is efficient enough in that case.
*/
- if (attr->ia_size) {
+ if (newsize) {
struct shmem_inode_info *info = SHMEM_I(inode);
spin_lock(&info->lock);
info->flags &= ~SHMEM_PAGEIN;
spin_unlock(&info->lock);
}
}
+
+ error = simple_setsize(inode, newsize);
+ if (error)
+ return error;
+ shmem_truncate_range(inode, newsize, (loff_t)-1);
+ attr->ia_valid &= ~ATTR_SIZE;
}

error = inode_change_ok(inode, attr);
@@ -822,11 +826,11 @@ static void shmem_delete_inode(struct in
{
struct shmem_inode_info *info = SHMEM_I(inode);

- if (inode->i_op->truncate == shmem_truncate) {
+ if (inode->i_mapping->a_ops == &shmem_aops) {
truncate_inode_pages(inode->i_mapping, 0);
shmem_unacct_size(info->flags, inode->i_size);
inode->i_size = 0;
- shmem_truncate(inode);
+ shmem_truncate_range(inode, 0, (loff_t)-1);
if (!list_empty(&info->swaplist)) {
mutex_lock(&shmem_swaplist_mutex);
list_del_init(&info->swaplist);
@@ -2018,7 +2022,6 @@ static const struct inode_operations shm
};

static const struct inode_operations shmem_symlink_inode_operations = {
- .truncate = shmem_truncate,
.readlink = generic_readlink,
.follow_link = shmem_follow_link,
.put_link = shmem_put_link,
@@ -2438,7 +2441,7 @@ static const struct file_operations shme
};

static const struct inode_operations shmem_inode_operations = {
- .truncate = shmem_truncate,
+ .new_truncate = 1,
.setattr = shmem_notify_change,
.truncate_range = shmem_truncate_range,
#ifdef CONFIG_TMPFS_POSIX_ACL
Index: linux-2.6/fs/ext2/ext2.h
===================================================================
--- linux-2.6.orig/fs/ext2/ext2.h
+++ linux-2.6/fs/ext2/ext2.h
@@ -122,7 +122,6 @@ extern int ext2_write_inode (struct inod
extern void ext2_delete_inode (struct inode *);
extern int ext2_sync_inode (struct inode *);
extern int ext2_get_block(struct inode *, sector_t, struct buffer_head *, int);
-extern void ext2_truncate (struct inode *);
extern int ext2_setattr (struct dentry *, struct iattr *);
extern void ext2_set_inode_flags(struct inode *inode);
extern void ext2_get_inode_flags(struct ext2_inode_info *);
Index: linux-2.6/fs/ext2/file.c
===================================================================
--- linux-2.6.orig/fs/ext2/file.c
+++ linux-2.6/fs/ext2/file.c
@@ -77,13 +77,13 @@ const struct file_operations ext2_xip_fi
#endif

const struct inode_operations ext2_file_inode_operations = {
- .truncate = ext2_truncate,
#ifdef CONFIG_EXT2_FS_XATTR
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,
.listxattr = ext2_listxattr,
.removexattr = generic_removexattr,
#endif
+ .new_truncate = 1,
.setattr = ext2_setattr,
.permission = ext2_permission,
.fiemap = ext2_fiemap,

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