Linux Kernel: fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek

Posted on by Tony In Linux, Linux Kernel, Programming

This change “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek” (commit 06222e4) in Linux kernel is authored by Josef Bacik <josef [at] redhat.com> on Mon Jul 18 13:21:38 2011 -0400.

Description of “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek”

The change “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek” introduces changes as follows.

fs: handle SEEK_HOLE/SEEK_DATA properly in all fs's that define their own llseek

This converts everybody to handle SEEK_HOLE/SEEK_DATA properly.  In some cases
we just return -EINVAL, in others we do the normal generic thing, and in others
we're simply making sure that the properly due-dilligence is done.  For example
in NFS/CIFS we need to make sure the file size is update properly for the
SEEK_HOLE and SEEK_DATA case, but since it calls the generic llseek stuff itself
that is all we have to do.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Linux kernel code changes from “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek”

There are 78 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 fs/block_dev.c   | 11 ++++++++---
 fs/ceph/dir.c    |  8 +++++++-
 fs/ceph/file.c   | 20 ++++++++++++++++++--
 fs/cifs/cifsfs.c |  7 +++++--
 fs/fuse/file.c   | 21 +++++++++++++++++++--
 fs/hpfs/dir.c    |  4 ++++
 fs/nfs/file.c    |  7 +++++--
 7 files changed, 66 insertions(+), 12 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 610e8e0b04b8..966617a422d9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -355,20 +355,25 @@ static loff_t block_llseek(struct file *file, loff_t offset, int origin)
    mutex_lock(&bd_inode->i_mutex);
    size = i_size_read(bd_inode);

+   retval = -EINVAL;
    switch (origin) {
-       case 2:
+       case SEEK_END:
            offset += size;
            break;
-       case 1:
+       case SEEK_CUR:
            offset += file->f_pos;
+       case SEEK_SET:
+           break;
+       default:
+           goto out;
    }
-   retval = -EINVAL;
    if (offset >= 0 && offset <= size) {
        if (offset != file->f_pos) {
            file->f_pos = offset;
        }
        retval = offset;
    }
+out:
    mutex_unlock(&bd_inode->i_mutex);
    return retval;
 }
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index e8477dc51b45..0972b457a03f 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -446,14 +446,19 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int origin)
    loff_t retval;

    mutex_lock(&inode->i_mutex);
+   retval = -EINVAL;
    switch (origin) {
    case SEEK_END:
        offset += inode->i_size + 2;   /* FIXME */
        break;
    case SEEK_CUR:
        offset += file->f_pos;
+   case SEEK_SET:
+       break;
+   default:
+       goto out;
    }
-   retval = -EINVAL;
+
    if (offset >= 0 && offset <= inode->i_sb->s_maxbytes) {
        if (offset != file->f_pos) {
            file->f_pos = offset;
@@ -477,6 +482,7 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int origin)
        if (offset > old_offset)
            fi->dir_release_count--;
    }
+out:
    mutex_unlock(&inode->i_mutex);
    return retval;
 }
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 0a292459c895..0d0eae05598f 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -768,13 +768,16 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int origin)

    mutex_lock(&inode->i_mutex);
    __ceph_do_pending_vmtruncate(inode);
-   switch (origin) {
-   case SEEK_END:
+   if (origin != SEEK_CUR || origin != SEEK_SET) {
        ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
        if (ret < 0) {
            offset = ret;
            goto out;
        }
+   }
+
+   switch (origin) {
+   case SEEK_END:
        offset += inode->i_size;
        break;
    case SEEK_CUR:
@@ -790,6 +793,19 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int origin)
        }
        offset += file->f_pos;
        break;
+   case SEEK_DATA:
+       if (offset >= inode->i_size) {
+           ret = -ENXIO;
+           goto out;
+       }
+       break;
+   case SEEK_HOLE:
+       if (offset >= inode->i_size) {
+           ret = -ENXIO;
+           goto out;
+       }
+       offset = inode->i_size;
+       break;
    }

    if (offset < 0 || offset > inode->i_sb->s_maxbytes) {
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index cbbb55e781d3..865517470967 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -704,8 +704,11 @@ static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,

 static loff_t cifs_llseek(struct file *file, loff_t offset, int origin)
 {
-   /* origin == SEEK_END => we must revalidate the cached file length */
-   if (origin == SEEK_END) {
+   /*
+    * origin == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
+    * the cached file length
+    */
+   if (origin != SEEK_SET || origin != SEEK_CUR) {
        int rc;
        struct inode *inode = file->f_path.dentry->d_inode;

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 82a66466a24c..73b89df20851 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1600,15 +1600,32 @@ static loff_t fuse_file_llseek(struct file *file, loff_t offset, int origin)
    struct inode *inode = file->f_path.dentry->d_inode;

    mutex_lock(&inode->i_mutex);
-   switch (origin) {
-   case SEEK_END:
+   if (origin != SEEK_CUR || origin != SEEK_SET) {
        retval = fuse_update_attributes(inode, NULL, file, NULL);
        if (retval)
            goto exit;
+   }
+
+   switch (origin) {
+   case SEEK_END:
        offset += i_size_read(inode);
        break;
    case SEEK_CUR:
        offset += file->f_pos;
+       break;
+   case SEEK_DATA:
+       if (offset >= i_size_read(inode)) {
+           retval = -ENXIO;
+           goto exit;
+       }
+       break;
+   case SEEK_HOLE:
+       if (offset >= i_size_read(inode)) {
+           retval = -ENXIO;
+           goto exit;
+       }
+       offset = i_size_read(inode);
+       break;
    }
    retval = -EINVAL;
    if (offset >= 0 && offset <= inode->i_sb->s_maxbytes) {
diff --git a/fs/hpfs/dir.c b/fs/hpfs/dir.c
index f46ae025bfb5..96a8ed91cedd 100644
--- a/fs/hpfs/dir.c
+++ b/fs/hpfs/dir.c
@@ -29,6 +29,10 @@ static loff_t hpfs_dir_lseek(struct file *filp, loff_t off, int whence)
    struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
    struct super_block *s = i->i_sb;

+   /* Somebody else will have to figure out what to do here */
+   if (whence == SEEK_DATA || whence == SEEK_HOLE)
+       return -EINVAL;
+
    hpfs_lock(s);

    /*printk("dir lseek\n");*/
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 2f093ed16980..2c1705b6acd7 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -187,8 +187,11 @@ static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
            filp->f_path.dentry->d_name.name,
            offset, origin);

-   /* origin == SEEK_END => we must revalidate the cached file length */
-   if (origin == SEEK_END) {
+   /*
+    * origin == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
+    * the cached file length
+    */
+   if (origin != SEEK_SET || origin != SEEK_CUR) {
        struct inode *inode = filp->f_mapping->host;

        int retval = nfs_revalidate_file_size(inode, filp);

The commit for this change in Linux stable tree is 06222e4 (patch).

Read more:

Tony

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