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/openbmc/linux/fs/notify/
H A Dfsnotify.hdiff fc1b1e135c3f72382f792e6c319fc088d5523ad5 Sun May 12 06:30:07 CDT 2024 Amir Goldstein <amir73il@gmail.com> fsnotify: clear PARENT_WATCHED flags lazily

[ Upstream commit 172e422ffea20a89bfdc672741c1aad6fbb5044e ]

In some setups directories can have many (usually negative) dentries.
Hence __fsnotify_update_child_dentry_flags() function can take a
significant amount of time. Since the bulk of this function happens
under inode->i_lock this causes a significant contention on the lock
when we remove the watch from the directory as the
__fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask()
races with __fsnotify_update_child_dentry_flags() calls from
__fsnotify_parent() happening on children. This can lead upto softlockup
reports reported by users.

Fix the problem by calling fsnotify_update_children_dentry_flags() to
set PARENT_WATCHED flags only when parent starts watching children.

When parent stops watching children, clear false positive PARENT_WATCHED
flags lazily in __fsnotify_parent() for each accessed child.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
H A Dmark.cdiff fc1b1e135c3f72382f792e6c319fc088d5523ad5 Sun May 12 06:30:07 CDT 2024 Amir Goldstein <amir73il@gmail.com> fsnotify: clear PARENT_WATCHED flags lazily

[ Upstream commit 172e422ffea20a89bfdc672741c1aad6fbb5044e ]

In some setups directories can have many (usually negative) dentries.
Hence __fsnotify_update_child_dentry_flags() function can take a
significant amount of time. Since the bulk of this function happens
under inode->i_lock this causes a significant contention on the lock
when we remove the watch from the directory as the
__fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask()
races with __fsnotify_update_child_dentry_flags() calls from
__fsnotify_parent() happening on children. This can lead upto softlockup
reports reported by users.

Fix the problem by calling fsnotify_update_children_dentry_flags() to
set PARENT_WATCHED flags only when parent starts watching children.

When parent stops watching children, clear false positive PARENT_WATCHED
flags lazily in __fsnotify_parent() for each accessed child.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
H A Dfsnotify.cdiff fc1b1e135c3f72382f792e6c319fc088d5523ad5 Sun May 12 06:30:07 CDT 2024 Amir Goldstein <amir73il@gmail.com> fsnotify: clear PARENT_WATCHED flags lazily

[ Upstream commit 172e422ffea20a89bfdc672741c1aad6fbb5044e ]

In some setups directories can have many (usually negative) dentries.
Hence __fsnotify_update_child_dentry_flags() function can take a
significant amount of time. Since the bulk of this function happens
under inode->i_lock this causes a significant contention on the lock
when we remove the watch from the directory as the
__fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask()
races with __fsnotify_update_child_dentry_flags() calls from
__fsnotify_parent() happening on children. This can lead upto softlockup
reports reported by users.

Fix the problem by calling fsnotify_update_children_dentry_flags() to
set PARENT_WATCHED flags only when parent starts watching children.

When parent stops watching children, clear false positive PARENT_WATCHED
flags lazily in __fsnotify_parent() for each accessed child.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
/openbmc/linux/include/linux/
H A Dfsnotify_backend.hdiff fc1b1e135c3f72382f792e6c319fc088d5523ad5 Sun May 12 06:30:07 CDT 2024 Amir Goldstein <amir73il@gmail.com> fsnotify: clear PARENT_WATCHED flags lazily

[ Upstream commit 172e422ffea20a89bfdc672741c1aad6fbb5044e ]

In some setups directories can have many (usually negative) dentries.
Hence __fsnotify_update_child_dentry_flags() function can take a
significant amount of time. Since the bulk of this function happens
under inode->i_lock this causes a significant contention on the lock
when we remove the watch from the directory as the
__fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask()
races with __fsnotify_update_child_dentry_flags() calls from
__fsnotify_parent() happening on children. This can lead upto softlockup
reports reported by users.

Fix the problem by calling fsnotify_update_children_dentry_flags() to
set PARENT_WATCHED flags only when parent starts watching children.

When parent stops watching children, clear false positive PARENT_WATCHED
flags lazily in __fsnotify_parent() for each accessed child.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>