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[GFS2] Alter direct I/O path
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As per comments received, alter the GFS2 direct I/O path so that
it uses the standard read functions "out of the box". Needs a
small change to one of the VFS functions. This reduces the size
of the code quite a lot and also removes the need for one new export.

Some more work remains to be done, but this is the bones of the
thing.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
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Steven Whitehouse committed Jul 25, 2006
1 parent 52f341c commit a9e5f4d
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Showing 3 changed files with 21 additions and 207 deletions.
54 changes: 16 additions & 38 deletions fs/gfs2/ops_address.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -589,24 +589,30 @@ static void gfs2_invalidatepage(struct page *page, unsigned long offset)
return;
}

static ssize_t gfs2_direct_IO_write(struct kiocb *iocb, const struct iovec *iov,
loff_t offset, unsigned long nr_segs)
static ssize_t gfs2_direct_IO(int rw, struct kiocb *iocb,
const struct iovec *iov, loff_t offset,
unsigned long nr_segs)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_holder gh;
int rv;

if (rw == READ)
mutex_lock(&inode->i_mutex);
/*
* Shared lock, even though its write, since we do no allocation
* Shared lock, even if its a write, since we do no allocation
* on this path. All we need change is atime.
*/
gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME, &gh);
rv = gfs2_glock_nq_m_atime(1, &gh);
if (rv)
goto out;

if (offset > i_size_read(inode))
goto out;

/*
* Should we return an error here? I can't see that O_DIRECT for
* a journaled file makes any sense. For now we'll silently fall
Expand All @@ -619,47 +625,19 @@ static ssize_t gfs2_direct_IO_write(struct kiocb *iocb, const struct iovec *iov,
if (gfs2_is_stuffed(ip))
goto out;

rv = __blockdev_direct_IO(WRITE, iocb, inode, inode->i_sb->s_bdev,
iov, offset, nr_segs, gfs2_get_block,
NULL, DIO_OWN_LOCKING);
rv = blockdev_direct_IO_own_locking(rw, iocb, inode,
inode->i_sb->s_bdev,
iov, offset, nr_segs,
gfs2_get_block, NULL);
out:
gfs2_glock_dq_m(1, &gh);
gfs2_holder_uninit(&gh);
if (rw == READ)
mutex_unlock(&inode->i_mutex);

return rv;
}

/**
* gfs2_direct_IO
*
* This is called with a shared lock already held for the read path.
* Currently, no locks are held when the write path is called.
*/
static ssize_t gfs2_direct_IO(int rw, struct kiocb *iocb,
const struct iovec *iov, loff_t offset,
unsigned long nr_segs)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);
int ret;

if (rw == WRITE)
return gfs2_direct_IO_write(iocb, iov, offset, nr_segs);

if (gfs2_assert_warn(sdp, gfs2_glock_is_locked_by_me(ip->i_gl)) ||
gfs2_assert_warn(sdp, !gfs2_is_stuffed(ip)))
return -EINVAL;

mutex_lock(&inode->i_mutex);
ret = __blockdev_direct_IO(READ, iocb, inode, inode->i_sb->s_bdev, iov,
offset, nr_segs, gfs2_get_block, NULL,
DIO_OWN_LOCKING);
mutex_unlock(&inode->i_mutex);
return ret;
}

/**
* stuck_releasepage - We're stuck in gfs2_releasepage(). Print stuff out.
* @bh: the buffer we're stuck on
Expand Down Expand Up @@ -765,7 +743,7 @@ int gfs2_releasepage(struct page *page, gfp_t gfp_mask)
}
while (bh != head);

out:
out:
return try_to_free_buffers(page);
}

Expand Down
170 changes: 3 additions & 167 deletions fs/gfs2/ops_file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -148,170 +148,6 @@ static loff_t gfs2_llseek(struct file *file, loff_t offset, int origin)
return error;
}


static ssize_t gfs2_direct_IO_read(struct kiocb *iocb, const struct iovec *iov,
loff_t offset, unsigned long nr_segs)
{
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
ssize_t retval;

retval = filemap_write_and_wait(mapping);
if (retval == 0) {
retval = mapping->a_ops->direct_IO(READ, iocb, iov, offset,
nr_segs);
}
return retval;
}

/**
* __gfs2_file_aio_read - The main GFS2 read function
*
* N.B. This is almost, but not quite the same as __generic_file_aio_read()
* the important subtle different being that inode->i_size isn't valid
* unless we are holding a lock, and we do this _only_ on the O_DIRECT
* path since otherwise locking is done entirely at the page cache
* layer.
*/
static ssize_t __gfs2_file_aio_read(struct kiocb *iocb,
const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos)
{
struct file *filp = iocb->ki_filp;
struct gfs2_inode *ip = GFS2_I(filp->f_mapping->host);
struct gfs2_holder gh;
ssize_t retval;
unsigned long seg;
size_t count;

count = 0;
for (seg = 0; seg < nr_segs; seg++) {
const struct iovec *iv = &iov[seg];

/*
* If any segment has a negative length, or the cumulative
* length ever wraps negative then return -EINVAL.
*/
count += iv->iov_len;
if (unlikely((ssize_t)(count|iv->iov_len) < 0))
return -EINVAL;
if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
continue;
if (seg == 0)
return -EFAULT;
nr_segs = seg;
count -= iv->iov_len; /* This segment is no good */
break;
}

/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
if (filp->f_flags & O_DIRECT) {
loff_t pos = *ppos, size;
struct address_space *mapping;
struct inode *inode;

mapping = filp->f_mapping;
inode = mapping->host;
retval = 0;
if (!count)
goto out; /* skip atime */

gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME, &gh);
retval = gfs2_glock_nq_m_atime(1, &gh);
if (retval)
goto out;
if (gfs2_is_stuffed(ip)) {
gfs2_glock_dq_m(1, &gh);
gfs2_holder_uninit(&gh);
goto fallback_to_normal;
}
size = i_size_read(inode);
if (pos < size) {
retval = gfs2_direct_IO_read(iocb, iov, pos, nr_segs);
if (retval > 0 && !is_sync_kiocb(iocb))
retval = -EIOCBQUEUED;
if (retval > 0)
*ppos = pos + retval;
}
file_accessed(filp);
gfs2_glock_dq_m(1, &gh);
gfs2_holder_uninit(&gh);
goto out;
}

fallback_to_normal:
retval = 0;
if (count) {
for (seg = 0; seg < nr_segs; seg++) {
read_descriptor_t desc;

desc.written = 0;
desc.arg.buf = iov[seg].iov_base;
desc.count = iov[seg].iov_len;
if (desc.count == 0)
continue;
desc.error = 0;
do_generic_file_read(filp,ppos,&desc,file_read_actor);
retval += desc.written;
if (desc.error) {
retval = retval ?: desc.error;
break;
}
}
}
out:
return retval;
}

/**
* gfs2_read - Read bytes from a file
* @file: The file to read from
* @buf: The buffer to copy into
* @size: The amount of data requested
* @offset: The current file offset
*
* Outputs: Offset - updated according to number of bytes read
*
* Returns: The number of bytes read, errno on failure
*/

static ssize_t gfs2_read(struct file *filp, char __user *buf, size_t size,
loff_t *offset)
{
struct iovec local_iov = { .iov_base = buf, .iov_len = size };
struct kiocb kiocb;
ssize_t ret;

init_sync_kiocb(&kiocb, filp);
ret = __gfs2_file_aio_read(&kiocb, &local_iov, 1, offset);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&kiocb);
return ret;
}

static ssize_t gfs2_file_readv(struct file *filp, const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos)
{
struct kiocb kiocb;
ssize_t ret;

init_sync_kiocb(&kiocb, filp);
ret = __gfs2_file_aio_read(&kiocb, iov, nr_segs, ppos);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&kiocb);
return ret;
}

static ssize_t gfs2_file_aio_read(struct kiocb *iocb, char __user *buf,
size_t count, loff_t pos)
{
struct iovec local_iov = { .iov_base = buf, .iov_len = count };

BUG_ON(iocb->ki_pos != pos);
return __gfs2_file_aio_read(iocb, &local_iov, 1, &iocb->ki_pos);
}


/**
* filldir_reg_func - Report a directory entry to the caller of gfs2_dir_read()
* @opaque: opaque data used by the function
Expand Down Expand Up @@ -949,9 +785,9 @@ static int gfs2_flock(struct file *file, int cmd, struct file_lock *fl)

const struct file_operations gfs2_file_fops = {
.llseek = gfs2_llseek,
.read = gfs2_read,
.readv = gfs2_file_readv,
.aio_read = gfs2_file_aio_read,
.read = generic_file_read,
.readv = generic_file_readv,
.aio_read = generic_file_aio_read,
.write = generic_file_write,
.writev = generic_file_writev,
.aio_write = generic_file_aio_write,
Expand Down
4 changes: 2 additions & 2 deletions mm/filemap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1122,7 +1122,6 @@ int file_read_actor(read_descriptor_t *desc, struct page *page,
desc->arg.buf += size;
return size;
}
EXPORT_SYMBOL_GPL(file_read_actor);

/**
* __generic_file_aio_read - generic filesystem read routine
Expand Down Expand Up @@ -1184,7 +1183,8 @@ __generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
*ppos = pos + retval;
}
file_accessed(filp);
goto out;
if (retval != 0)
goto out;
}

retval = 0;
Expand Down

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