Tejun Heo 044e3bc333 sysfs: use generic_file_llseek() for sysfs_file_operations ... 13c589d5b0 ("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>		2013-11-01 12:13:37 -07:00
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dir.c	sysfs: separate out dup filename warning into a separate function	2013-10-29 15:12:07 -07:00
file.c	sysfs: use generic_file_llseek() for sysfs_file_operations	2013-11-01 12:13:37 -07:00
group.c	sysfs: introduce [__]sysfs_remove()	2013-10-03 16:38:52 -07:00
inode.c	sysfs: move sysfs_hash_and_remove() to fs/sysfs/dir.c	2013-10-29 15:12:07 -07:00
Kconfig	kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT	2011-01-20 17:02:05 -08:00
Makefile	sysfs: merge regular and bin file handling	2013-10-05 17:27:40 -07:00
mount.c	sysfs: drop kobj_ns_type handling	2013-09-26 15:30:22 -07:00
symlink.c	sysfs: remove sysfs_addrm_cxt->parent_sd	2013-10-03 16:16:43 -07:00
sysfs.h	sysfs: separate out dup filename warning into a separate function	2013-10-29 15:12:07 -07:00