[PATCH 6/7] xfs: Factor xfs_seek_hole_data into helper

Eric Sandeen
2016-01-22T18:25:42Z

Factor xfs_seek_hole_data into an unlocked helper which takes
an xfs inode rather than a file for internal use.

Also allow specification of "end" - the vfs lseek interface is
defined such that any offset past eof/i_size shall return -ENXIO,
but we will use this for quota code which does not maintain i_size,
and we want to be able to SEEK_DATA past i_size as well. So the
lseek path can send in i_size, and the quota code can determine
its own ending offset.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---
fs/xfs/xfs_file.c | 82 ++++++++++++++++++++++++++++++++++++----------------
fs/xfs/xfs_inode.h | 2 +
2 files changed, 59 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index ebe9b82..5dc7113 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1337,31 +1337,31 @@ out:
return found;
}

-STATIC loff_t
-xfs_seek_hole_data(
- struct file *file,
+/*
+ * caller must lock inode with xfs_ilock_data_map_shared,
+ * can we craft an appropriate ASSERT?
+ *
+ * end is because the VFS-level lseek interface is defined such that any
+ * offset past i_size shall return -ENXIO, but we use this for quota code
+ * which does not maintain i_size, and we want to SEEK_DATA past i_size.
+ */
+loff_t
+__xfs_seek_hole_data(
+ struct inode *inode,
loff_t start,
+ loff_t end,
int whence)
{
- struct inode *inode = file->f_mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
loff_t uninitialized_var(offset);
- xfs_fsize_t isize;
xfs_fileoff_t fsbno;
- xfs_filblks_t end;
- uint lock;
+ xfs_filblks_t lastbno;
int error;

- if (XFS_FORCED_SHUTDOWN(mp))
- return -EIO;
-
- lock = xfs_ilock_data_map_shared(ip);
-
- isize = i_size_read(inode);
- if (start >= isize) {
+ if (start >= end) {
error = -ENXIO;
- goto out_unlock;
+ goto out_error;
}

/*
@@ -1369,22 +1369,22 @@ xfs_seek_hole_data(
* by fsbno to the end block of the file.
*/
fsbno = XFS_B_TO_FSBT(mp, start);
- end = XFS_B_TO_FSB(mp, isize);
+ lastbno = XFS_B_TO_FSB(mp, end);

for (;;) {
struct xfs_bmbt_irec map[2];
int nmap = 2;
unsigned int i;

- error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
+ error = xfs_bmapi_read(ip, fsbno, lastbno - fsbno, map, &nmap,
XFS_BMAPI_ENTIRE);
if (error)
- goto out_unlock;
+ goto out_error;

/* No extents at given offset, must be beyond EOF */
if (nmap == 0) {
error = -ENXIO;
- goto out_unlock;
+ goto out_error;
}

for (i = 0; i < nmap; i++) {
@@ -1426,7 +1426,7 @@ xfs_seek_hole_data(
* hole at the end of any file).
*/
if (whence == SEEK_HOLE) {
- offset = isize;
+ offset = end;
break;
}
/*
@@ -1434,7 +1434,7 @@ xfs_seek_hole_data(
*/
ASSERT(whence == SEEK_DATA);
error = -ENXIO;
- goto out_unlock;
+ goto out_error;
}

ASSERT(i > 1);
@@ -1445,14 +1445,14 @@ xfs_seek_hole_data(
*/
fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
start = XFS_FSB_TO_B(mp, fsbno);
- if (start >= isize) {
+ if (start >= end) {
if (whence == SEEK_HOLE) {
- offset = isize;
+ offset = end;
break;
}
ASSERT(whence == SEEK_DATA);
error = -ENXIO;
- goto out_unlock;
+ goto out_error;
}
}

@@ -1464,7 +1464,39 @@ out:
* situation in particular.
*/
if (whence == SEEK_HOLE)
- offset = min_t(loff_t, offset, isize);
+ offset = min_t(loff_t, offset, end);
+
+ return offset;
+
+out_error:
+ return error;
+}
+
+STATIC loff_t
+xfs_seek_hole_data(
+ struct file *file,
+ loff_t start,
+ int whence)
+{
+ struct inode *inode = file->f_mapping->host;
+ struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_mount *mp = ip->i_mount;
+ uint lock;
+ loff_t offset, end;
+ int error = 0;
+
+ if (XFS_FORCED_SHUTDOWN(mp))
+ return -EIO;
+
+ lock = xfs_ilock_data_map_shared(ip);
+
+ end = i_size_read(inode);
+ offset = __xfs_seek_hole_data(inode, start, end, whence);
+ if (offset < 0) {
+ error = offset;
+ goto out_unlock;
+ }
+
offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);

out_unlock:
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index ca9e119..ed7e933 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -437,6 +437,8 @@ int xfs_update_prealloc_flags(struct xfs_inode *ip,
int xfs_zero_eof(struct xfs_inode *ip, xfs_off_t offset,
xfs_fsize_t isize, bool *did_zeroing);
int xfs_iozero(struct xfs_inode *ip, loff_t pos, size_t count);
+loff_t __xfs_seek_hole_data(struct inode *inode, loff_t start,
+ loff_t eof, int whence);

/* from xfs_iops.c */
--
1.7.1