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lookup_open(): lock the parent shared unless O_CREAT is given

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-04-28 19:35:16 -04:00
parent 6fbd07146d
commit 9cf843e3f4
2 changed files with 12 additions and 3 deletions
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3
Documentation/filesystems/porting
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@ -575,3 +575,6 @@ in your dentry operations instead.
Old method is only used if the new one is absent; eventually it will
be removed. Switch while you still can; the old one won't stay.
--
[mandatory]
->atomic_open() calls without O_CREAT may happen in parallel.

12
fs/namei.c
View File

@ -3084,7 +3084,7 @@ static int do_last(struct nameidata *nd,
}
retry_lookup:
if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
error = mnt_want_write(nd->path.mnt);
if (!error)
got_write = true;
@ -3094,9 +3094,15 @@ static int do_last(struct nameidata *nd,
* dropping this one anyway.
*/
}
inode_lock(dir->d_inode);
if (open_flag & O_CREAT)
inode_lock(dir->d_inode);
else
inode_lock_shared(dir->d_inode);
error = lookup_open(nd, &path, file, op, got_write, opened);
inode_unlock(dir->d_inode);
if (open_flag & O_CREAT)
inode_unlock(dir->d_inode);
else
inode_unlock_shared(dir->d_inode);
if (error <= 0) {
if (error)