diff options
| author | Amir Goldstein | 2019-06-07 17:24:38 +0300 |
|---|---|---|
| committer | Jeff Layton | 2019-06-19 08:49:38 -0400 |
| commit | 387e3746d01c34457d6a73688acd90428725070b (patch) | |
| tree | 575796428aac6a85321113d53a75abe9cfdccbcf /include | |
| parent | d51f527f44f96276a94c191bc160de051f64aeea (diff) | |
locks: eliminate false positive conflicts for write lease
check_conflicting_open() is checking for existing fd's open for read or
for write before allowing to take a write lease. The check that was
implemented using i_count and d_count is an approximation that has
several false positives. For example, overlayfs since v4.19, takes an
extra reference on the dentry; An open with O_PATH takes a reference on
the dentry although the file cannot be read nor written.
Change the implementation to use i_readcount and i_writecount to
eliminate the false positive conflicts and allow a write lease to be
taken on an overlayfs file.
The change of behavior with existing fd's open with O_PATH is symmetric
w.r.t. current behavior of lease breakers - an open with O_PATH currently
does not break a write lease.
This increases the size of struct inode by 4 bytes on 32bit archs when
CONFIG_FILE_LOCKING is defined and CONFIG_IMA was not already
defined.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/fs.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index f7fdfe93e25d..419e327022de 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -694,7 +694,7 @@ struct inode { atomic_t i_count; atomic_t i_dio_count; atomic_t i_writecount; -#ifdef CONFIG_IMA +#if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING) atomic_t i_readcount; /* struct files open RO */ #endif union { @@ -2890,7 +2890,7 @@ static inline bool inode_is_open_for_write(const struct inode *inode) return atomic_read(&inode->i_writecount) > 0; } -#ifdef CONFIG_IMA +#if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING) static inline void i_readcount_dec(struct inode *inode) { BUG_ON(!atomic_read(&inode->i_readcount)); |