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xfs: remove the i_new_size field in struct xfs_inode

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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 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>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This commit is contained in:
Christoph Hellwig
2011-12-18 20:00:12 +00:00
committed by Ben Myers
parent ce7ae151dd
commit 2813d682e8
5 changed files with 30 additions and 92 deletions
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72
fs/xfs/xfs_file.c
View File

@@ -412,27 +412,6 @@ xfs_file_splice_read(
return ret;
}
/*
* 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,
@@ -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;
}