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-rw-r--r--fs/ubifs/gc.c6
-rw-r--r--fs/ubifs/misc.h17
-rw-r--r--fs/ubifs/tnc.c109
-rw-r--r--fs/ubifs/ubifs.h6
4 files changed, 87 insertions, 51 deletions
diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
index d0f3dac2908..13f1019c859 100644
--- a/fs/ubifs/gc.c
+++ b/fs/ubifs/gc.c
@@ -344,6 +344,12 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
if (err)
goto out;
+ /* Allow for races with TNC */
+ c->gced_lnum = lnum;
+ smp_wmb();
+ c->gc_seq += 1;
+ smp_wmb();
+
if (c->gc_lnum == -1) {
c->gc_lnum = lnum;
err = LEB_RETAINED;
diff --git a/fs/ubifs/misc.h b/fs/ubifs/misc.h
index 87dabf9fe74..87ced4c74a6 100644
--- a/fs/ubifs/misc.h
+++ b/fs/ubifs/misc.h
@@ -325,4 +325,21 @@ static inline struct timespec ubifs_current_time(struct inode *inode)
current_fs_time(inode->i_sb) : CURRENT_TIME_SEC;
}
+/**
+ * ubifs_tnc_lookup - look up a file-system node.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ *
+ * This function look up and reads node with key @key. The caller has to make
+ * sure the @node buffer is large enough to fit the node. Returns zero in case
+ * of success, %-ENOENT if the node was not found, and a negative error code in
+ * case of failure.
+ */
+static inline int ubifs_tnc_lookup(struct ubifs_info *c,
+ const union ubifs_key *key, void *node)
+{
+ return ubifs_tnc_locate(c, key, node, NULL, NULL);
+}
+
#endif /* __UBIFS_MISC_H__ */
diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 4fbc5921688..7da209ab937 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -506,7 +506,7 @@ static int fallible_read_node(struct ubifs_info *c, const union ubifs_key *key,
if (keys_cmp(c, key, &node_key) != 0)
ret = 0;
}
- if (ret == 0)
+ if (ret == 0 && c->replaying)
dbg_mnt("dangling branch LEB %d:%d len %d, key %s",
zbr->lnum, zbr->offs, zbr->len, DBGKEY(key));
return ret;
@@ -1382,50 +1382,39 @@ static int lookup_level0_dirty(struct ubifs_info *c, const union ubifs_key *key,
}
/**
- * ubifs_tnc_lookup - look up a file-system node.
+ * maybe_leb_gced - determine if a LEB may have been garbage collected.
* @c: UBIFS file-system description object
- * @key: node key to lookup
- * @node: the node is returned here
+ * @lnum: LEB number
+ * @gc_seq1: garbage collection sequence number
*
- * This function look up and reads node with key @key. The caller has to make
- * sure the @node buffer is large enough to fit the node. Returns zero in case
- * of success, %-ENOENT if the node was not found, and a negative error code in
- * case of failure.
+ * This function determines if @lnum may have been garbage collected since
+ * sequence number @gc_seq1. If it may have been then %1 is returned, otherwise
+ * %0 is returned.
*/
-int ubifs_tnc_lookup(struct ubifs_info *c, const union ubifs_key *key,
- void *node)
+static int maybe_leb_gced(struct ubifs_info *c, int lnum, int gc_seq1)
{
- int found, n, err;
- struct ubifs_znode *znode;
- struct ubifs_zbranch zbr, *zt;
-
- mutex_lock(&c->tnc_mutex);
- found = ubifs_lookup_level0(c, key, &znode, &n);
- if (!found) {
- err = -ENOENT;
- goto out;
- } else if (found < 0) {
- err = found;
- goto out;
- }
- zt = &znode->zbranch[n];
- if (is_hash_key(c, key)) {
- /*
- * In this case the leaf node cache gets used, so we pass the
- * address of the zbranch and keep the mutex locked
- */
- err = tnc_read_node_nm(c, zt, node);
- goto out;
- }
- zbr = znode->zbranch[n];
- mutex_unlock(&c->tnc_mutex);
-
- err = ubifs_tnc_read_node(c, &zbr, node);
- return err;
+ int gc_seq2, gced_lnum;
-out:
- mutex_unlock(&c->tnc_mutex);
- return err;
+ gced_lnum = c->gced_lnum;
+ smp_rmb();
+ gc_seq2 = c->gc_seq;
+ /* Same seq means no GC */
+ if (gc_seq1 == gc_seq2)
+ return 0;
+ /* Different by more than 1 means we don't know */
+ if (gc_seq1 + 1 != gc_seq2)
+ return 1;
+ /*
+ * We have seen the sequence number has increased by 1. Now we need to
+ * be sure we read the right LEB number, so read it again.
+ */
+ smp_rmb();
+ if (gced_lnum != c->gced_lnum)
+ return 1;
+ /* Finally we can check lnum */
+ if (gced_lnum == lnum)
+ return 1;
+ return 0;
}
/**
@@ -1436,16 +1425,19 @@ out:
* @lnum: LEB number is returned here
* @offs: offset is returned here
*
- * This function is the same as 'ubifs_tnc_lookup()' but it returns the node
- * location also. See 'ubifs_tnc_lookup()'.
+ * This function look up and reads node with key @key. The caller has to make
+ * sure the @node buffer is large enough to fit the node. Returns zero in case
+ * of success, %-ENOENT if the node was not found, and a negative error code in
+ * case of failure. The node location can be returned in @lnum and @offs.
*/
int ubifs_tnc_locate(struct ubifs_info *c, const union ubifs_key *key,
void *node, int *lnum, int *offs)
{
- int found, n, err;
+ int found, n, err, safely = 0, gc_seq1;
struct ubifs_znode *znode;
struct ubifs_zbranch zbr, *zt;
+again:
mutex_lock(&c->tnc_mutex);
found = ubifs_lookup_level0(c, key, &znode, &n);
if (!found) {
@@ -1456,24 +1448,43 @@ int ubifs_tnc_locate(struct ubifs_info *c, const union ubifs_key *key,
goto out;
}
zt = &znode->zbranch[n];
+ if (lnum) {
+ *lnum = zt->lnum;
+ *offs = zt->offs;
+ }
if (is_hash_key(c, key)) {
/*
* In this case the leaf node cache gets used, so we pass the
* address of the zbranch and keep the mutex locked
*/
- *lnum = zt->lnum;
- *offs = zt->offs;
err = tnc_read_node_nm(c, zt, node);
goto out;
}
+ if (safely) {
+ err = ubifs_tnc_read_node(c, zt, node);
+ goto out;
+ }
+ /* Drop the TNC mutex prematurely and race with garbage collection */
zbr = znode->zbranch[n];
+ gc_seq1 = c->gc_seq;
mutex_unlock(&c->tnc_mutex);
- *lnum = zbr.lnum;
- *offs = zbr.offs;
+ if (ubifs_get_wbuf(c, zbr.lnum)) {
+ /* We do not GC journal heads */
+ err = ubifs_tnc_read_node(c, &zbr, node);
+ return err;
+ }
- err = ubifs_tnc_read_node(c, &zbr, node);
- return err;
+ err = fallible_read_node(c, key, &zbr, node);
+ if (maybe_leb_gced(c, zbr.lnum, gc_seq1)) {
+ /*
+ * The node may have been GC'ed out from under us so try again
+ * while keeping the TNC mutex locked.
+ */
+ safely = 1;
+ goto again;
+ }
+ return 0;
out:
mutex_unlock(&c->tnc_mutex);
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index d7f706f7a30..7828d69ca4f 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1028,6 +1028,8 @@ struct ubifs_mount_opts {
* @sbuf: a buffer of LEB size used by GC and replay for scanning
* @idx_gc: list of index LEBs that have been garbage collected
* @idx_gc_cnt: number of elements on the idx_gc list
+ * @gc_seq: incremented for every non-index LEB garbage collected
+ * @gced_lnum: last non-index LEB that was garbage collected
*
* @infos_list: links all 'ubifs_info' objects
* @umount_mutex: serializes shrinker and un-mount
@@ -1257,6 +1259,8 @@ struct ubifs_info {
void *sbuf;
struct list_head idx_gc;
int idx_gc_cnt;
+ volatile int gc_seq;
+ volatile int gced_lnum;
struct list_head infos_list;
struct mutex umount_mutex;
@@ -1451,8 +1455,6 @@ int ubifs_save_dirty_idx_lnums(struct ubifs_info *c);
/* tnc.c */
int ubifs_lookup_level0(struct ubifs_info *c, const union ubifs_key *key,
struct ubifs_znode **zn, int *n);
-int ubifs_tnc_lookup(struct ubifs_info *c, const union ubifs_key *key,
- void *node);
int ubifs_tnc_lookup_nm(struct ubifs_info *c, const union ubifs_key *key,
void *node, const struct qstr *nm);
int ubifs_tnc_locate(struct ubifs_info *c, const union ubifs_key *key,
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-12 16:47:12 +0000