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Subject[PATCH 5.10 113/157] gfs2: move freeze glock outside the make_fs_rw and _ro functions
Date
From: Bob Peterson <rpeterso@redhat.com>

[ Upstream commit 96b1454f2e8ede4c619fde405a1bb4e9ba8d218e ]

Before this patch, sister functions gfs2_make_fs_rw and gfs2_make_fs_ro locked
(held) the freeze glock by calling gfs2_freeze_lock and gfs2_freeze_unlock.
The problem is, not all the callers of gfs2_make_fs_ro should be doing this.
The three callers of gfs2_make_fs_ro are: remount (gfs2_reconfigure),
signal_our_withdraw, and unmount (gfs2_put_super). But when unmounting the
file system we can get into the following circular lock dependency:

deactivate_super
down_write(&s->s_umount); <-------------------------------------- s_umount
deactivate_locked_super
gfs2_kill_sb
kill_block_super
generic_shutdown_super
gfs2_put_super
gfs2_make_fs_ro
gfs2_glock_nq_init sd_freeze_gl
freeze_go_sync
if (freeze glock in SH)
freeze_super (vfs)
down_write(&sb->s_umount); <------- s_umount

This patch moves the hold of the freeze glock outside the two sister rw/ro
functions to their callers, but it doesn't request the glock from
gfs2_put_super, thus eliminating the circular dependency.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/gfs2/ops_fstype.c | 31 +++++++++++++++++--------------
fs/gfs2/super.c | 23 -----------------------
fs/gfs2/util.c | 18 ++++++++++++++++--
3 files changed, 33 insertions(+), 39 deletions(-)

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 4ee56f5e93cb..f2c6bbe5cdb8 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1084,6 +1084,7 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
int silent = fc->sb_flags & SB_SILENT;
struct gfs2_sbd *sdp;
struct gfs2_holder mount_gh;
+ struct gfs2_holder freeze_gh;
int error;

sdp = init_sbd(sb);
@@ -1195,23 +1196,18 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
goto fail_per_node;
}

- if (sb_rdonly(sb)) {
- struct gfs2_holder freeze_gh;
+ error = gfs2_freeze_lock(sdp, &freeze_gh, 0);
+ if (error)
+ goto fail_per_node;

- error = gfs2_freeze_lock(sdp, &freeze_gh, 0);
- if (error) {
- fs_err(sdp, "can't make FS RO: %d\n", error);
- goto fail_per_node;
- }
- gfs2_freeze_unlock(&freeze_gh);
- } else {
+ if (!sb_rdonly(sb))
error = gfs2_make_fs_rw(sdp);
- if (error) {
- fs_err(sdp, "can't make FS RW: %d\n", error);
- goto fail_per_node;
- }
- }

+ gfs2_freeze_unlock(&freeze_gh);
+ if (error) {
+ fs_err(sdp, "can't make FS RW: %d\n", error);
+ goto fail_per_node;
+ }
gfs2_glock_dq_uninit(&mount_gh);
gfs2_online_uevent(sdp);
return 0;
@@ -1512,6 +1508,12 @@ static int gfs2_reconfigure(struct fs_context *fc)
fc->sb_flags |= SB_RDONLY;

if ((sb->s_flags ^ fc->sb_flags) & SB_RDONLY) {
+ struct gfs2_holder freeze_gh;
+
+ error = gfs2_freeze_lock(sdp, &freeze_gh, 0);
+ if (error)
+ return -EINVAL;
+
if (fc->sb_flags & SB_RDONLY) {
error = gfs2_make_fs_ro(sdp);
if (error)
@@ -1521,6 +1523,7 @@ static int gfs2_reconfigure(struct fs_context *fc)
if (error)
errorfc(fc, "unable to remount read-write");
}
+ gfs2_freeze_unlock(&freeze_gh);
}
sdp->sd_args = *newargs;

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 6b0e8c0bb110..ddd40c96f7a2 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -165,7 +165,6 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
{
struct gfs2_inode *ip = GFS2_I(sdp->sd_jdesc->jd_inode);
struct gfs2_glock *j_gl = ip->i_gl;
- struct gfs2_holder freeze_gh;
struct gfs2_log_header_host head;
int error;

@@ -173,10 +172,6 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
if (error)
return error;

- error = gfs2_freeze_lock(sdp, &freeze_gh, 0);
- if (error)
- goto fail_threads;
-
j_gl->gl_ops->go_inval(j_gl, DIO_METADATA);
if (gfs2_withdrawn(sdp)) {
error = -EIO;
@@ -203,13 +198,9 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)

set_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

- gfs2_freeze_unlock(&freeze_gh);
-
return 0;

fail:
- gfs2_freeze_unlock(&freeze_gh);
-fail_threads:
if (sdp->sd_quotad_process)
kthread_stop(sdp->sd_quotad_process);
sdp->sd_quotad_process = NULL;
@@ -609,21 +600,9 @@ static void gfs2_dirty_inode(struct inode *inode, int flags)

int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
{
- struct gfs2_holder freeze_gh;
int error = 0;
int log_write_allowed = test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

- gfs2_holder_mark_uninitialized(&freeze_gh);
- if (sdp->sd_freeze_gl &&
- !gfs2_glock_is_locked_by_me(sdp->sd_freeze_gl)) {
- error = gfs2_freeze_lock(sdp, &freeze_gh,
- log_write_allowed ? 0 : LM_FLAG_TRY);
- if (error == GLR_TRYFAILED)
- error = 0;
- if (error && !gfs2_withdrawn(sdp))
- return error;
- }
-
gfs2_flush_delete_work(sdp);
if (!log_write_allowed && current == sdp->sd_quotad_process)
fs_warn(sdp, "The quotad daemon is withdrawing.\n");
@@ -652,8 +631,6 @@ int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
atomic_read(&sdp->sd_reserving_log) == 0,
HZ * 5);
}
- gfs2_freeze_unlock(&freeze_gh);
-
gfs2_quota_cleanup(sdp);

if (!log_write_allowed)
diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
index c8d55055e495..a1ecb2b48250 100644
--- a/fs/gfs2/util.c
+++ b/fs/gfs2/util.c
@@ -123,6 +123,7 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_glock *i_gl = ip->i_gl;
u64 no_formal_ino = ip->i_no_formal_ino;
+ int log_write_allowed = test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
int ret = 0;
int tries;

@@ -143,8 +144,21 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
* therefore we need to clear SDF_JOURNAL_LIVE manually.
*/
clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
- if (!sb_rdonly(sdp->sd_vfs))
- ret = gfs2_make_fs_ro(sdp);
+ if (!sb_rdonly(sdp->sd_vfs)) {
+ struct gfs2_holder freeze_gh;
+
+ gfs2_holder_mark_uninitialized(&freeze_gh);
+ if (sdp->sd_freeze_gl &&
+ !gfs2_glock_is_locked_by_me(sdp->sd_freeze_gl)) {
+ ret = gfs2_freeze_lock(sdp, &freeze_gh,
+ log_write_allowed ? 0 : LM_FLAG_TRY);
+ if (ret == GLR_TRYFAILED)
+ ret = 0;
+ }
+ if (!ret)
+ ret = gfs2_make_fs_ro(sdp);
+ gfs2_freeze_unlock(&freeze_gh);
+ }

if (sdp->sd_lockstruct.ls_ops->lm_lock == NULL) { /* lock_nolock */
if (!ret)
--
2.30.1


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