[PATCH 09/11] xfs: remove the i_new_size field in struct xfs_inode

Christoph Hellwig
2011-12-08T15:59:21Z

[-- Attachment #1: xfs-kill-i_new_size --]
[-- Type: text/plain, Size: 13732 bytes --]

Now that we use the VFS i_size field throughout XFS there is no need for the
i_new_size field any more given that the VFS i_size field gets updated
in ->write_end before unlocking the page, and thus is a) always uptodate when
writeback could see a page. Removing i_new_size also has the advantage that
we will never have to trim back di_size during a failed buffered write,
given that it never gets updated past i_size.

Note that currently the generic direct I/O code only updates i_size after
calling our end_io handler, which requires a small workaround to make
sure di_size actually makes it to disk. I hope to fix this properly in
the generic code.

A downside is that we lose the support for parallel non-overlapping O_DIRECT
appending writes that recently was added. I don't think keeping the complex
and fragile i_new_size infrastructure for this is a good tradeoff - if we
really care about parallel appending writers we should investigate turning
the iolock into a range lock, which would also allow for parallel
non-overlapping buffered writers.

Signed-off-by: Christoph Hellwig <hch@lst.de>

---
fs/xfs/xfs_aops.c | 28 +++++++++++---------
fs/xfs/xfs_file.c | 72 +++++++----------------------------------------------
fs/xfs/xfs_iget.c | 1
fs/xfs/xfs_inode.h | 2 -
fs/xfs/xfs_trace.h | 18 ++-----------
5 files changed, 29 insertions(+), 92 deletions(-)

Index: xfs/fs/xfs/xfs_file.c
===================================================================
--- xfs.orig/fs/xfs/xfs_file.c 2011-11-30 12:59:11.669698558 +0100
+++ xfs/fs/xfs/xfs_file.c 2011-11-30 12:59:13.533021797 +0100
@@ -413,27 +413,6 @@ xfs_file_splice_read(
}

/*
- * If this was a direct or synchronous I/O that failed (such as ENOSPC) then
- * part of the I/O may have been written to disk before the error occurred. In
- * this case the on-disk file size may have been adjusted beyond the in-memory
- * file size and now needs to be truncated back.
- */
-STATIC void
-xfs_aio_write_newsize_update(
- struct xfs_inode *ip,
- xfs_fsize_t new_size)
-{
- if (new_size == ip->i_new_size) {
- xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
- if (new_size == ip->i_new_size)
- ip->i_new_size = 0;
- if (ip->i_d.di_size > i_size_read(VFS_I(ip)))
- ip->i_d.di_size = i_size_read(VFS_I(ip));
- xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
- }
-}
-
-/*
* xfs_file_splice_write() does not use xfs_rw_ilock() because
* generic_file_splice_write() takes the i_mutex itself. This, in theory,
* couuld cause lock inversions between the aio_write path and the splice path
@@ -451,7 +430,6 @@ xfs_file_splice_write(
{
struct inode *inode = outfilp->f_mapping->host;
struct xfs_inode *ip = XFS_I(inode);
- xfs_fsize_t new_size;
int ioflags = 0;
ssize_t ret;

@@ -465,20 +443,12 @@ xfs_file_splice_write(

xfs_ilock(ip, XFS_IOLOCK_EXCL);

- new_size = *ppos + count;
-
- xfs_ilock(ip, XFS_ILOCK_EXCL);
- if (new_size > i_size_read(inode))
- ip->i_new_size = new_size;
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
-
trace_xfs_file_splice_write(ip, count, *ppos, ioflags);

ret = generic_file_splice_write(pipe, outfilp, ppos, count, flags);
if (ret > 0)
XFS_STATS_ADD(xs_write_bytes, ret);

- xfs_aio_write_newsize_update(ip, new_size);
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
return ret;
}
@@ -673,16 +643,13 @@ xfs_file_aio_write_checks(
struct file *file,
loff_t *pos,
size_t *count,
- xfs_fsize_t *new_sizep,
int *iolock)
{
struct inode *inode = file->f_mapping->host;
struct xfs_inode *ip = XFS_I(inode);
- xfs_fsize_t new_size;
int error = 0;

xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
- *new_sizep = 0;
restart:
error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
if (error) {
@@ -697,15 +664,13 @@ restart:
/*
* If the offset is beyond the size of the file, we need to zero any
* blocks that fall between the existing EOF and the start of this
- * write. There is no need to issue zeroing if another in-flght IO ends
- * at or before this one If zeronig is needed and we are currently
- * holding the iolock shared, we need to update it to exclusive which
- * involves dropping all locks and relocking to maintain correct locking
- * order. If we do this, restart the function to ensure all checks and
- * values are still valid.
+ * write. If zeroing is needed and we are currently holding the
+ * iolock shared, we need to update it to exclusive which involves
+ * dropping all locks and relocking to maintain correct locking order.
+ * If we do this, restart the function to ensure all checks and values
+ * are still valid.
*/
- if ((ip->i_new_size && *pos > ip->i_new_size) ||
- (!ip->i_new_size && *pos > i_size_read(inode))) {
+ if (*pos > i_size_read(inode)) {
if (*iolock == XFS_IOLOCK_SHARED) {
xfs_rw_iunlock(ip, XFS_ILOCK_EXCL | *iolock);
*iolock = XFS_IOLOCK_EXCL;
@@ -714,19 +679,6 @@ restart:
}
error = -xfs_zero_eof(ip, *pos, i_size_read(inode));
}
-
- /*
- * If this IO extends beyond EOF, we may need to update ip->i_new_size.
- * We have already zeroed space beyond EOF (if necessary). Only update
- * ip->i_new_size if this IO ends beyond any other in-flight writes.
- */
- new_size = *pos + *count;
- if (new_size > i_size_read(inode)) {
- if (new_size > ip->i_new_size)
- ip->i_new_size = new_size;
- *new_sizep = new_size;
- }
-
xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
if (error)
return error;
@@ -772,7 +724,6 @@ xfs_file_dio_aio_write(
unsigned long nr_segs,
loff_t pos,
size_t ocount,
- xfs_fsize_t *new_size,
int *iolock)
{
struct file *file = iocb->ki_filp;
@@ -817,7 +768,7 @@ xfs_file_dio_aio_write(
xfs_rw_ilock(ip, *iolock);
}

- ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
+ ret = xfs_file_aio_write_checks(file, &pos, &count, iolock);
if (ret)
return ret;

@@ -855,7 +806,6 @@ xfs_file_buffered_aio_write(
unsigned long nr_segs,
loff_t pos,
size_t ocount,
- xfs_fsize_t *new_size,
int *iolock)
{
struct file *file = iocb->ki_filp;
@@ -869,7 +819,7 @@ xfs_file_buffered_aio_write(
*iolock = XFS_IOLOCK_EXCL;
xfs_rw_ilock(ip, *iolock);

- ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
+ ret = xfs_file_aio_write_checks(file, &pos, &count, iolock);
if (ret)
return ret;

@@ -909,7 +859,6 @@ xfs_file_aio_write(
ssize_t ret;
int iolock;
size_t ocount = 0;
- xfs_fsize_t new_size = 0;

XFS_STATS_INC(xs_write_calls);

@@ -929,10 +878,10 @@ xfs_file_aio_write(

if (unlikely(file->f_flags & O_DIRECT))
ret = xfs_file_dio_aio_write(iocb, iovp, nr_segs, pos,
- ocount, &new_size, &iolock);
+ ocount, &iolock);
else
ret = xfs_file_buffered_aio_write(iocb, iovp, nr_segs, pos,
- ocount, &new_size, &iolock);
+ ocount, &iolock);

if (ret <= 0)
goto out_unlock;
@@ -953,7 +902,6 @@ xfs_file_aio_write(
}

out_unlock:
- xfs_aio_write_newsize_update(ip, new_size);
xfs_rw_iunlock(ip, iolock);
return ret;
}
Index: xfs/fs/xfs/xfs_aops.c
===================================================================
--- xfs.orig/fs/xfs/xfs_aops.c 2011-11-30 12:59:11.669698558 +0100
+++ xfs/fs/xfs/xfs_aops.c 2011-12-01 08:12:10.946664057 +0100
@@ -111,8 +111,7 @@ xfs_ioend_new_eof(
xfs_fsize_t bsize;

bsize = ioend->io_offset + ioend->io_size;
- isize = MAX(i_size_read(VFS_I(ip)), ip->i_new_size);
- isize = MIN(isize, bsize);
+ isize = MIN(i_size_read(VFS_I(ip)), bsize);
return isize > ip->i_d.di_size ? isize : 0;
}

@@ -126,11 +125,7 @@ static inline bool xfs_ioend_is_append(s
}

/*
- * Update on-disk file size now that data has been written to disk. The
- * current in-memory file size is i_size. If a write is beyond eof i_new_size
- * will be the intended file size until i_size is updated. If this write does
- * not extend all the way to the valid file size then restrict this update to
- * the end of the write.
+ * Update on-disk file size now that data has been written to disk.
*
* This function does not block as blocking on the inode lock in IO completion
* can lead to IO completion order dependency deadlocks.. If it can't get the
@@ -1279,6 +1274,15 @@ xfs_end_io_direct_write(
struct xfs_ioend *ioend = iocb->private;

/*
+ * While the generic direct I/O code updates the inode size, it does
+ * so only after the end_io handler is called, which means our
+ * end_io handler thinks the on-disk size is outside the in-core
+ * size. To prevent this just update it a little bit earlier here.
+ */
+ if (offset + size > i_size_read(ioend->io_inode))
+ i_size_write(ioend->io_inode, offset + size);
+
+ /*
* blockdev_direct_IO can return an error even after the I/O
* completion handler was called. Thus we need to protect
* against double-freeing.
@@ -1340,12 +1344,10 @@ xfs_vm_write_failed(

if (to > inode->i_size) {
/*
- * punch out the delalloc blocks we have already allocated. We
- * don't call xfs_setattr() to do this as we may be in the
- * middle of a multi-iovec write and so the vfs inode->i_size
- * will not match the xfs ip->i_size and so it will zero too
- * much. Hence we jus truncate the page cache to zero what is
- * necessary and punch the delalloc blocks directly.
+ * Punch out the delalloc blocks we have already allocated.
+ *
+ * Don't bother with xfs_setattr given that nothing can have
+ * it do disk yet as the page is still locked at this point.
*/
struct xfs_inode *ip = XFS_I(inode);
xfs_fileoff_t start_fsb;
Index: xfs/fs/xfs/xfs_iget.c
===================================================================
--- xfs.orig/fs/xfs/xfs_iget.c 2011-11-30 12:59:11.676365190 +0100
+++ xfs/fs/xfs/xfs_iget.c 2011-11-30 12:59:13.533021797 +0100
@@ -94,7 +94,6 @@ xfs_inode_alloc(
ip->i_update_core = 0;
ip->i_delayed_blks = 0;
memset(&ip->i_d, 0, sizeof(xfs_icdinode_t));
- ip->i_new_size = 0;

return ip;
}
Index: xfs/fs/xfs/xfs_trace.h
===================================================================
--- xfs.orig/fs/xfs/xfs_trace.h 2011-11-30 12:59:11.673031874 +0100
+++ xfs/fs/xfs/xfs_trace.h 2011-11-30 12:59:13.536355113 +0100
@@ -891,7 +891,6 @@ DECLARE_EVENT_CLASS(xfs_file_class,
__field(dev_t, dev)
__field(xfs_ino_t, ino)
__field(xfs_fsize_t, size)
- __field(xfs_fsize_t, new_size)
__field(loff_t, offset)
__field(size_t, count)
__field(int, flags)
@@ -900,17 +899,15 @@ DECLARE_EVENT_CLASS(xfs_file_class,
__entry->dev = VFS_I(ip)->i_sb->s_dev;
__entry->ino = ip->i_ino;
__entry->size = ip->i_d.di_size;
- __entry->new_size = ip->i_new_size;
__entry->offset = offset;
__entry->count = count;
__entry->flags = flags;
),
- TP_printk("dev %d:%d ino 0x%llx size 0x%llx new_size 0x%llx "
+ TP_printk("dev %d:%d ino 0x%llx size 0x%llx "
"offset 0x%llx count 0x%zx ioflags %s",
MAJOR(__entry->dev), MINOR(__entry->dev),
__entry->ino,
__entry->size,
- __entry->new_size,
__entry->offset,
__entry->count,
__print_flags(__entry->flags, "|", XFS_IO_FLAGS))
@@ -978,7 +975,6 @@ DECLARE_EVENT_CLASS(xfs_imap_class,
__field(dev_t, dev)
__field(xfs_ino_t, ino)
__field(loff_t, size)
- __field(loff_t, new_size)
__field(loff_t, offset)
__field(size_t, count)
__field(int, type)
@@ -990,7 +986,6 @@ DECLARE_EVENT_CLASS(xfs_imap_class,
__entry->dev = VFS_I(ip)->i_sb->s_dev;
__entry->ino = ip->i_ino;
__entry->size = ip->i_d.di_size;
- __entry->new_size = ip->i_new_size;
__entry->offset = offset;
__entry->count = count;
__entry->type = type;
@@ -998,13 +993,11 @@ DECLARE_EVENT_CLASS(xfs_imap_class,
__entry->startblock = irec ? irec->br_startblock : 0;
__entry->blockcount = irec ? irec->br_blockcount : 0;
),
- TP_printk("dev %d:%d ino 0x%llx size 0x%llx new_size 0x%llx "
- "offset 0x%llx count %zd type %s "
- "startoff 0x%llx startblock %lld blockcount 0x%llx",
+ TP_printk("dev %d:%d ino 0x%llx size 0x%llx offset 0x%llx count %zd "
+ "type %s startoff 0x%llx startblock %lld blockcount 0x%llx",
MAJOR(__entry->dev), MINOR(__entry->dev),
__entry->ino,
__entry->size,
- __entry->new_size,
__entry->offset,
__entry->count,
__print_symbolic(__entry->type, XFS_IO_TYPES),
@@ -1031,7 +1024,6 @@ DECLARE_EVENT_CLASS(xfs_simple_io_class,
__field(xfs_ino_t, ino)
__field(loff_t, isize)
__field(loff_t, disize)
- __field(loff_t, new_size)
__field(loff_t, offset)
__field(size_t, count)
),
@@ -1040,17 +1032,15 @@ DECLARE_EVENT_CLASS(xfs_simple_io_class,
__entry->ino = ip->i_ino;
__entry->isize = VFS_I(ip)->i_size;
__entry->disize = ip->i_d.di_size;
- __entry->new_size = ip->i_new_size;
__entry->offset = offset;
__entry->count = count;
),
- TP_printk("dev %d:%d ino 0x%llx isize 0x%llx disize 0x%llx new_size 0x%llx "
+ TP_printk("dev %d:%d ino 0x%llx isize 0x%llx disize 0x%llx "
"offset 0x%llx count %zd",
MAJOR(__entry->dev), MINOR(__entry->dev),
__entry->ino,
__entry->isize,
__entry->disize,
- __entry->new_size,
__entry->offset,
__entry->count)
);
Index: xfs/fs/xfs/xfs_inode.h
===================================================================
--- xfs.orig/fs/xfs/xfs_inode.h 2011-11-30 12:59:11.679698505 +0100
+++ xfs/fs/xfs/xfs_inode.h 2011-12-01 08:12:10.839997391 +0100
@@ -246,8 +246,6 @@ typedef struct xfs_inode {

xfs_icdinode_t i_d; /* most of ondisk inode */

- xfs_fsize_t i_new_size; /* size when write completes */
-
/* VFS inode */
struct inode i_vnode; /* embedded VFS inode */
} xfs_inode_t;