From: Abhijith Das <adas@redhat.com> Subject: [RHEL5.1 PATCH][GFS2] bz 272021: GFS2 - flocks from same process trip kernel BUG at fs/gfs2/glock.c:1118! Date: Fri, 14 Sep 2007 08:36:17 -0500 Bugzilla: 272021 Message-Id: <46EA8E51.9000309@redhat.com> Changelog: [gfs2] allow process to handle multiple flocks on a file This patch adds a new flag to the gfs2_holder structure GL_FLOCK. It is set on holders of glocks representing flocks. This flag is checked in add_to_queue() and a process is permitted to queue more than one holder onto a glock if it is set. This solves the issue of a process not being able to do multiple flocks on the same file. Through a single descriptor, a process can now promote and demote flocks. Through multiple descriptors a process can now queue multiple flocks on the same file. There's still the problem of a process deadlocking itself (because gfs2 blocking locks are not interruptible) by queueing incompatible flocks. Signed-off-by: Abhijith Das <adas@redhat.com> Index: linux-2.6.18.noarch/fs/gfs2/glock.c =================================================================== --- linux-2.6.18.noarch.orig/fs/gfs2/glock.c 2007-09-14 08:25:30.000000000 -0500 +++ linux-2.6.18.noarch/fs/gfs2/glock.c 2007-09-14 08:27:55.000000000 -0500 @@ -1105,24 +1105,31 @@ if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags)) BUG(); - existing = find_holder_by_owner(&gl->gl_holders, gh->gh_owner_pid); - if (existing) { - print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip); - printk(KERN_INFO "pid : %d\n", existing->gh_owner_pid); - printk(KERN_INFO "lock type : %d lock state : %d\n", - existing->gh_gl->gl_name.ln_type, existing->gh_gl->gl_state); - print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip); - printk(KERN_INFO "pid : %d\n", gh->gh_owner_pid); - printk(KERN_INFO "lock type : %d lock state : %d\n", - gl->gl_name.ln_type, gl->gl_state); - BUG(); - } - - existing = find_holder_by_owner(&gl->gl_waiters3, gh->gh_owner_pid); - if (existing) { - print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip); - print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip); - BUG(); + if (!(gh->gh_flags & GL_FLOCK)) { + existing = find_holder_by_owner(&gl->gl_holders, + gh->gh_owner_pid); + if (existing) { + print_symbol(KERN_WARNING "original: %s\n", + existing->gh_ip); + printk(KERN_INFO "pid : %d\n", existing->gh_owner_pid); + printk(KERN_INFO "lock type : %d lock state : %d\n", + existing->gh_gl->gl_name.ln_type, + existing->gh_gl->gl_state); + print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip); + printk(KERN_INFO "pid : %d\n", gh->gh_owner_pid); + printk(KERN_INFO "lock type : %d lock state : %d\n", + gl->gl_name.ln_type, gl->gl_state); + BUG(); + } + + existing = find_holder_by_owner(&gl->gl_waiters3, + gh->gh_owner_pid); + if (existing) { + print_symbol(KERN_WARNING "original: %s\n", + existing->gh_ip); + print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip); + BUG(); + } } if (gh->gh_flags & LM_FLAG_PRIORITY) Index: linux-2.6.18.noarch/fs/gfs2/glock.h =================================================================== --- linux-2.6.18.noarch.orig/fs/gfs2/glock.h 2007-09-14 08:25:30.000000000 -0500 +++ linux-2.6.18.noarch/fs/gfs2/glock.h 2007-09-14 08:26:24.000000000 -0500 @@ -25,6 +25,7 @@ #define GL_SKIP 0x00000100 #define GL_ATIME 0x00000200 #define GL_NOCACHE 0x00000400 +#define GL_FLOCK 0x00000800 #define GL_NOCANCEL 0x00001000 #define GLR_TRYFAILED 13 Index: linux-2.6.18.noarch/fs/gfs2/ops_file.c =================================================================== --- linux-2.6.18.noarch.orig/fs/gfs2/ops_file.c 2007-09-14 08:25:30.000000000 -0500 +++ linux-2.6.18.noarch/fs/gfs2/ops_file.c 2007-09-14 08:26:51.000000000 -0500 @@ -550,7 +550,8 @@ int error = 0; state = (fl->fl_type == F_WRLCK) ? LM_ST_EXCLUSIVE : LM_ST_SHARED; - flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY) | GL_EXACT | GL_NOCACHE; + flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY) | GL_EXACT | GL_NOCACHE + | GL_FLOCK; mutex_lock(&fp->f_fl_mutex); @@ -558,21 +559,19 @@ if (gl) { if (fl_gh->gh_state == state) goto out; - gfs2_glock_hold(gl); flock_lock_file_wait(file, &(struct file_lock){.fl_type = F_UNLCK}); - gfs2_glock_dq_uninit(fl_gh); + gfs2_glock_dq_wait(fl_gh); + gfs2_holder_reinit(state, flags, fl_gh); } else { error = gfs2_glock_get(GFS2_SB(&ip->i_inode), ip->i_no_addr, &gfs2_flock_glops, CREATE, &gl); if (error) goto out; + gfs2_holder_init(gl, state, flags, fl_gh); + gfs2_glock_put(gl); } - - gfs2_holder_init(gl, state, flags, fl_gh); - gfs2_glock_put(gl); - error = gfs2_glock_nq(fl_gh); if (error) { gfs2_holder_uninit(fl_gh);