Commit 9c225f2655 ("vfs: atomic f_pos accesses as per POSIX") may have
gone a little too far: We've had a report of a deadlock of an
application accessing a /proc file through the same file descriptor
from multiple threads. While /proc files are regular ones, them (and
similarly others which are) often not being seekable really already
makes them deviate from how regular files would behave.
Since for non-seekable files the file position is kind of a strange
thing anyway, also don't enforce atomic position updates for them.
(I do recognize that the application isn't really standard conforming,
as it should use multiple file descriptors from all I understand. But
it worked fine before that change, and so they claim the kernel to be
at fault.)
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
---
fs/open.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- 4.6-rc2/fs/open.c
+++ 4.6-rc2-nonseekable-no-atomic-pos/fs/open.c
@@ -1142,7 +1142,8 @@ EXPORT_SYMBOL(generic_file_open);
*/
int nonseekable_open(struct inode *inode, struct file *filp)
{
- filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+ filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE |
+ FMODE_ATOMIC_POS);
return 0;
}
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