From 7d95c8f27d9be65bf160f1edaf653d33dfceb58c Mon Sep 17 00:00:00 2001 From: dean gaudet Date: Fri, 3 Feb 2006 03:04:30 -0800 Subject: [PATCH] [PATCH] fcntl F_SETFL and read-only IS_APPEND files There is code in setfl() which attempts to preserve the O_APPEND flag on IS_APPEND files... however IS_APPEND files could also be opened O_RDONLY and in that case setfl() should not require O_APPEND... coreutils 5.93 tail -f attempts to set O_NONBLOCK even on regular files... unfortunately if you try this on an append-only log file the result is this: fcntl64(3, F_GETFL) = 0x8000 (flags O_RDONLY|O_LARGEFILE) fcntl64(3, F_SETFL, O_RDONLY|O_NONBLOCK|O_LARGEFILE) = -1 EPERM (Operation not permitted) I offer up the patch below as one way of fixing the problem... i've tested it fixes the problem with tail -f but haven't really tested beyond that. (I also reported the coreutils bug upstream... it shouldn't fail imho... ) Signed-off-by: dean gaudet Cc: Al Viro Acked-by: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fcntl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/fcntl.c b/fs/fcntl.c index 5f96786d1c73..dc4a7007f4e7 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -208,8 +208,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg) struct inode * inode = filp->f_dentry->d_inode; int error = 0; - /* O_APPEND cannot be cleared if the file is marked as append-only */ - if (!(arg & O_APPEND) && IS_APPEND(inode)) + /* + * O_APPEND cannot be cleared if the file is marked as append-only + * and the file is open for write. + */ + if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode)) return -EPERM; /* O_NOATIME can only be set by the owner or superuser */