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| author | Tejun Heo <tj@kernel.org> | 2013-11-01 18:16:53 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-11-01 20:13:37 +0100 |
| commit | 044e3bc33391b1f2769d5ab2c04f246c3d8e04c3 (patch) | |
| tree | 6f4d8ec0abfb0f47682e2d57e8ed2ae127474a07 /fs/sysfs | |
| parent | sysfs: return correct error code on unimplemented mmap() (diff) | |
| download | linux-044e3bc33391b1f2769d5ab2c04f246c3d8e04c3.tar.xz linux-044e3bc33391b1f2769d5ab2c04f246c3d8e04c3.zip | |
sysfs: use generic_file_llseek() for sysfs_file_operations
13c589d5b0ac6 ("sysfs: use seq_file when reading regular files")
converted regular sysfs files to use seq_file. The commit substituted
generic_file_llseek() with seq_lseek() for llseek implementation.
Before the change, all regular sysfs files were allowed to seek to any
position in [0, PAGE_SIZE] as the file size is always PAGE_SIZE and
generic_file_llseek() allows any seeking inside the range under file
size; however, seq_lseek()'s behavior is different. It traverses the
output by repeatedly invoking ->show() until it reaches the target
offset or traversal indicates EOF. As seq_files are fully dynamic and
may not end at all, it doesn't support seeking from the end
(SEEK_END).
Apparently, there are userland tools which uses SEEK_END to discover
the buffer size to use and the switch to seq_lseek() disturbs them as
SEEK_END fails with -EINVAL.
The only benefits of using seq_lseek() instead of
generic_file_llseek() are
* Early failure. If traversing to certain file position should fail,
seq_lseek() will report such failures on lseek(2) instead of the
following read/write operations.
* EOF detection. While SEEK_END is not supported, SEEK_SET/CUR +
large offset can be used to detect eof - eof at the time of the seek
anyway as the file size may change dynamically.
Both aren't necessary for sysfs or prospect kernfs users. Revert to
genefic_file_llseek() and preserve the original behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Link: https://lkml.kernel.org/r/20131031114358.GA5551@osiris
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/sysfs')
| -rw-r--r-- | fs/sysfs/file.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 382db3c045f3..79b5da2acbe1 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -800,7 +800,7 @@ EXPORT_SYMBOL_GPL(sysfs_notify); const struct file_operations sysfs_file_operations = { .read = seq_read, .write = sysfs_write_file, - .llseek = seq_lseek, + .llseek = generic_file_llseek, .open = sysfs_open_file, .release = sysfs_release, .poll = sysfs_poll, |