On Mon, Jun 15, 2015 at 10:24:28AM +0200, Felix Fietkau wrote: > On 2015-06-15 10:20, Miklos Szeredi wrote: > > On Thu, Jun 11, 2015 at 2:01 PM, Miklos Szeredi <mszeredi@xxxxxxx> wrote: > >> On 7 May 2015 at 15:49, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: > >>> On 2015-05-07 08:01, Wojciech Dubowik wrote: > >>>> Try to boot with kernel locking enabled. I have seen jffs2 deadlocks on > >>>> readdir. As far as I remember > >>>> with this patch it went through but I don't know anymore whether I have > >>>> changed sth in config. > >>>> > >>>> Have a look at (search engine...) [PATCH] fs: jffs2: Add setup code for > >>>> spi nor flash. > >>>> > >>>> Even with this patch I got some possible dead lock warnings so it might > >>>> be just a partial cure. BTW it's > >>>> a bit scary for future use. Looks like jffs2 doesn't get enough care... > >>> I believe the locking issues are an overlayfs regression, maybe even > >>> the same one as this one (which I fixed years ago): > >>> http://linux-fsdevel.vger.kernel.narkive.com/XRtXLDlf/patch-1-2-overlayfs-fix-a-deadlock-in-ovl-dir-read-merged > >>> > >>> I believe this is the cause of the regression: > >>> > >>> commit 49c21e1cacd74a8c83407c70ad860c994e606e25 > >>> Author: Miklos Szeredi <mszeredi@xxxxxxx> > >>> Date: Sat Dec 13 00:59:42 2014 +0100 > >>> > >> > >> I'm working on 4.0 support for ar71xx and found that > >> /etc/rc.d/S00sysfixtime is not able to finish it's job after second > >> boot after flashing (t.i. after overlayfs is switched to jffs). I've > >> run strace and found that find hangs on the very last getdents64 call > >> (before calling it succesfully many times on previous > >> files/directories). > >> I've reverted every change up to > >> 49c21e1cacd74a8c83407c70ad860c994e606e25 to overlayfs and it started > >> working. Applying 49c21e1cacd74a8c83407c70ad860c994e606e25 back breaks > >> it. So this commit is indeed the cause of regression. > >> > >> Miklos, any ideas how to fix it in current tree? I'm using 4.0.5 now > >> but AFAIK there were no more changes to overlayfs. > > > > What's the full mount setup? (cat /proc/mounts) > /dev/root /rom squashfs ro,relatime 0 0 > proc /proc proc rw,noatime 0 0 > sysfs /sys sysfs rw,noatime 0 0 > tmpfs /tmp tmpfs rw,nosuid,nodev,noatime 0 0 > /dev/mtdblock8 /overlay jffs2 rw,noatime 0 0 > overlayfs:/overlay / overlay rw,noatime,lowerdir=/,upperdir=/overlay/upper,workdir=/overlay/work 0 0 > tmpfs /dev tmpfs rw,relatime,size=512k,mode=755 0 0 > devpts /dev/pts devpts rw,relatime,mode=600 0 0 > debugfs /sys/kernel/debug debugfs rw,noatime 0 0 > > - Felix Following patch should fix the locking issue. Please test. Thanks, Miklos --- fs/overlayfs/readdir.c | 77 +++++++++++++++++++++++++++++++------------------ 1 file changed, 49 insertions(+), 28 deletions(-) --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -23,6 +23,7 @@ struct ovl_cache_entry { u64 ino; struct list_head l_node; struct rb_node node; + struct ovl_cache_entry *next_maybe_whiteout; bool is_whiteout; char name[]; }; @@ -39,7 +40,7 @@ struct ovl_readdir_data { struct rb_root root; struct list_head *list; struct list_head middle; - struct dentry *dir; + struct ovl_cache_entry *first_maybe_whiteout; int count; int err; }; @@ -79,7 +80,7 @@ static struct ovl_cache_entry *ovl_cache return NULL; } -static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir, +static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd, const char *name, int len, u64 ino, unsigned int d_type) { @@ -98,29 +99,8 @@ static struct ovl_cache_entry *ovl_cache p->is_whiteout = false; if (d_type == DT_CHR) { - struct dentry *dentry; - const struct cred *old_cred; - struct cred *override_cred; - - override_cred = prepare_creds(); - if (!override_cred) { - kfree(p); - return NULL; - } - - /* - * CAP_DAC_OVERRIDE for lookup - */ - cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); - old_cred = override_creds(override_cred); - - dentry = lookup_one_len(name, dir, len); - if (!IS_ERR(dentry)) { - p->is_whiteout = ovl_is_whiteout(dentry); - dput(dentry); - } - revert_creds(old_cred); - put_cred(override_cred); + p->next_maybe_whiteout = rdd->first_maybe_whiteout; + rdd->first_maybe_whiteout = p; } return p; } @@ -148,7 +128,7 @@ static int ovl_cache_entry_add_rb(struct return 0; } - p = ovl_cache_entry_new(rdd->dir, name, len, ino, d_type); + p = ovl_cache_entry_new(rdd, name, len, ino, d_type); if (p == NULL) return -ENOMEM; @@ -169,7 +149,7 @@ static int ovl_fill_lower(struct ovl_rea if (p) { list_move_tail(&p->l_node, &rdd->middle); } else { - p = ovl_cache_entry_new(rdd->dir, name, namelen, ino, d_type); + p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type); if (p == NULL) rdd->err = -ENOMEM; else @@ -219,6 +199,43 @@ static int ovl_fill_merge(struct dir_con return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type); } +static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd) +{ + int err = 0; + + mutex_lock(&dir->d_inode->i_mutex); + while (rdd->first_maybe_whiteout) { + struct dentry *dentry; + const struct cred *old_cred; + struct cred *override_cred; + struct ovl_cache_entry *p = rdd->first_maybe_whiteout; + + rdd->first_maybe_whiteout = p->next_maybe_whiteout; + + override_cred = prepare_creds(); + if (!override_cred) { + err = -ENOMEM; + break; + } + /* + * CAP_DAC_OVERRIDE for lookup + */ + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + old_cred = override_creds(override_cred); + + dentry = lookup_one_len(p->name, dir, p->len); + if (!IS_ERR(dentry)) { + p->is_whiteout = ovl_is_whiteout(dentry); + dput(dentry); + } + revert_creds(old_cred); + put_cred(override_cred); + } + mutex_unlock(&dir->d_inode->i_mutex); + + return err; +} + static inline int ovl_dir_read(struct path *realpath, struct ovl_readdir_data *rdd) { @@ -229,7 +246,7 @@ static inline int ovl_dir_read(struct pa if (IS_ERR(realfile)) return PTR_ERR(realfile); - rdd->dir = realpath->dentry; + rdd->first_maybe_whiteout = NULL; rdd->ctx.pos = 0; do { rdd->count = 0; @@ -238,6 +255,10 @@ static inline int ovl_dir_read(struct pa if (err >= 0) err = rdd->err; } while (!err && rdd->count); + + if (!err && rdd->first_maybe_whiteout) + err = ovl_check_whiteouts(realpath->dentry, rdd); + fput(realfile); return err; -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
