[PATCH 2/2] Cygwin: lockf: Make lockf() return ENOLCK when too many locks
Takashi Yano
takashi.yano@nifty.ne.jp
Sun Oct 20 09:26:37 GMT 2024
Previously, lockf() printed a warning message when the number of locks
per file exceeds the limit (MAX_LOCKF_CNT). This patch makes lockf()
return ENOLCK in that case rather than printing the warning message.
Addresses: https://cygwin.com/pipermail/cygwin/2024-October/256528.html
Fixes: 31390e4ca643 ("(inode_t::get_all_locks_list): Use pre-allocated buffer in i_all_lf instead of allocating every lock. Return pointer to start of linked list of locks.")
Reported-by: Christian Franke <Christian.Franke@t-online.de>
Reviewed-by:
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
winsup/cygwin/flock.cc | 46 ++++++++++++++++++++++++++++++++++--------
1 file changed, 38 insertions(+), 8 deletions(-)
diff --git a/winsup/cygwin/flock.cc b/winsup/cygwin/flock.cc
index 5550b3a5b..3b8475c18 100644
--- a/winsup/cygwin/flock.cc
+++ b/winsup/cygwin/flock.cc
@@ -297,6 +297,7 @@ class inode_t
HANDLE i_dir;
HANDLE i_mtx;
uint32_t i_cnt; /* # of threads referencing this instance. */
+ uint32_t i_lock_cnt; /* # of locks for this file */
public:
inode_t (dev_t dev, ino_t ino);
@@ -321,6 +322,8 @@ class inode_t
void unlock_and_remove_if_unused ();
lockf_t *get_all_locks_list ();
+ uint32_t get_lock_count () /* needs get_all_locks_list() */
+ { return i_lock_cnt; }
bool del_my_locks (long long id, HANDLE fhdl);
};
@@ -503,7 +506,8 @@ inode_t::get (dev_t dev, ino_t ino, bool create_if_missing, bool lock)
}
inode_t::inode_t (dev_t dev, ino_t ino)
-: i_lockf (NULL), i_all_lf (NULL), i_dev (dev), i_ino (ino), i_cnt (0L)
+: i_lockf (NULL), i_all_lf (NULL), i_dev (dev), i_ino (ino), i_cnt (0L),
+ i_lock_cnt (0)
{
HANDLE parent_dir;
WCHAR name[48];
@@ -610,17 +614,15 @@ inode_t::get_all_locks_list ()
dbi->ObjectName.Buffer[LOCK_OBJ_NAME_LEN] = L'\0';
if (!newlock.from_obj_name (this, &i_all_lf, dbi->ObjectName.Buffer))
continue;
- if (lock - i_all_lf >= MAX_LOCKF_CNT)
- {
- system_printf ("Warning, can't handle more than %d locks per file.",
- MAX_LOCKF_CNT);
- break;
- }
+ if (lock - i_all_lf > MAX_LOCKF_CNT)
+ api_fatal ("Can't handle more than %d locks per file.",
+ MAX_LOCKF_CNT);
if (lock > i_all_lf)
lock[-1].lf_next = lock;
new (lock++) lockf_t (newlock);
}
}
+ i_lock_cnt = lock - i_all_lf;
/* If no lock has been found, return NULL. */
if (lock == i_all_lf)
return NULL;
@@ -1346,6 +1348,8 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
*
* Handle any locks that overlap.
*/
+ node->get_all_locks_list (); /* Update lock count */
+ const uint32_t lock_cnt = node->get_lock_count ();
prev = head;
block = *head;
needtolink = 1;
@@ -1368,6 +1372,8 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
case 0: /* no overlap */
if (needtolink)
{
+ if (lock_cnt + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
*prev = lock;
lock->lf_next = overlap;
lock->create_lock_obj ();
@@ -1399,12 +1405,20 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
}
if (overlap->lf_start == lock->lf_start)
{
+ if (lock_cnt + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
*prev = lock;
lock->lf_next = overlap;
overlap->lf_start = lock->lf_end + 1;
}
else
- lf_split (overlap, lock, clean);
+ {
+ if ((overlap->lf_end > lock->lf_end
+ && lock_cnt + 2 > MAX_LOCKF_CNT)
+ || lock_cnt + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
+ lf_split (overlap, lock, clean);
+ }
lf_wakelock (overlap, fhdl);
overlap->create_lock_obj ();
lock->create_lock_obj ();
@@ -1440,6 +1454,8 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
/*
* Add lock after overlap on the list.
*/
+ if (lock_cnt + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
lock->lf_next = overlap->lf_next;
overlap->lf_next = lock;
overlap->lf_end = lock->lf_start - 1;
@@ -1456,6 +1472,8 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
*/
if (needtolink)
{
+ if (lock_cnt + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
*prev = lock;
lock->lf_next = overlap;
lock->create_lock_obj ();
@@ -1483,12 +1501,24 @@ lf_clearlock (lockf_t *unlock, lockf_t **clean, HANDLE fhdl)
lockf_t *lf = *head;
lockf_t *overlap, **prev;
int ovcase;
+ inode_t *node = lf->lf_inode;
if (lf == NOLOCKF)
return 0;
prev = head;
while ((ovcase = lf_findoverlap (lf, unlock, SELF, &prev, &overlap)))
{
+ /* Check if # of locks will be increased. */
+ if (ovcase == 2 /* overlap contains lock */
+ && overlap->lf_start < unlock->lf_start
+ && overlap->lf_end > unlock->lf_end)
+ {
+ tmp_pathbuf tp;
+ node->i_all_lf = (lockf_t *) tp.w_get ();
+ node->get_all_locks_list (); /* Update lock count */
+ if (node->get_lock_count () + 1 > MAX_LOCKF_CNT)
+ return ENOLCK;
+ }
/*
* Wakeup the list of locks to be retried.
*/
--
2.45.1
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