diff options
| author | Valentine Sinitsyn <valesini@yandex-team.ru> | 2023-09-25 11:40:12 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-10-05 13:42:11 +0200 |
| commit | 0fedefd4c4e33dd24f726b13b5d7c143e2b483be (patch) | |
| tree | cf84459a4ef3e035265bd133847b1ea202d963ff /fs/sysfs | |
| parent | 7360a48bd0f5e62b2d00c387d5d3f2821eb290ce (diff) | |
kernfs: sysfs: support custom llseek method for sysfs entries
As of now, seeking in sysfs files is handled by generic_file_llseek().
There are situations where one may want to customize seeking logic:
- Many sysfs entries are fixed files while generic_file_llseek() accepts
past-the-end positions. Not only being useless by itself, this
also means a bug in userspace code will trigger not at lseek(), but at
some later point making debugging harder.
- generic_file_llseek() relies on f_mapping->host to get the file size
which might not be correct for all sysfs entries.
See commit 636b21b50152 ("PCI: Revoke mappings like devmem") as an example.
Implement llseek method to override this behavior at sysfs attribute
level. The method is optional, and if it is absent,
generic_file_llseek() is called to preserve backwards compatibility.
Signed-off-by: Valentine Sinitsyn <valesini@yandex-team.ru>
Link: https://lore.kernel.org/r/20230925084013.309399-1-valesini@yandex-team.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/sysfs')
| -rw-r--r-- | fs/sysfs/file.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index a12ac0356c69..6b7652fb8050 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -167,6 +167,18 @@ static int sysfs_kf_bin_mmap(struct kernfs_open_file *of, return battr->mmap(of->file, kobj, battr, vma); } +static loff_t sysfs_kf_bin_llseek(struct kernfs_open_file *of, loff_t offset, + int whence) +{ + struct bin_attribute *battr = of->kn->priv; + struct kobject *kobj = of->kn->parent->priv; + + if (battr->llseek) + return battr->llseek(of->file, kobj, battr, offset, whence); + else + return generic_file_llseek(of->file, offset, whence); +} + static int sysfs_kf_bin_open(struct kernfs_open_file *of) { struct bin_attribute *battr = of->kn->priv; @@ -249,6 +261,7 @@ static const struct kernfs_ops sysfs_bin_kfops_mmap = { .write = sysfs_kf_bin_write, .mmap = sysfs_kf_bin_mmap, .open = sysfs_kf_bin_open, + .llseek = sysfs_kf_bin_llseek, }; int sysfs_add_file_mode_ns(struct kernfs_node *parent, |