ocfs2: protect extent tree in ocfs2_prepare_inode_for_write()

When the extent tree is modified, it should be protected by inode
cluster lock and ip_alloc_sem.

The extent tree is accessed and modified in the
ocfs2_prepare_inode_for_write, but isn't protected by ip_alloc_sem.

The following is a case.  The function ocfs2_fiemap is accessing the
extent tree, which is modified at the same time.

  kernel BUG at fs/ocfs2/extent_map.c:475!
  invalid opcode: 0000 [#1] SMP
  Modules linked in: tun ocfs2 ocfs2_nodemanager configfs ocfs2_stackglue [...]
  CPU: 16 PID: 14047 Comm: o2info Not tainted 4.1.12-124.23.1.el6uek.x86_64 #2
  Hardware name: Oracle Corporation ORACLE SERVER X7-2L/ASM, MB MECH, X7-2L, BIOS 42040600 10/19/2018
  task: ffff88019487e200 ti: ffff88003daa4000 task.ti: ffff88003daa4000
  RIP: ocfs2_get_clusters_nocache.isra.11+0x390/0x550 [ocfs2]
  Call Trace:
    ocfs2_fiemap+0x1e3/0x430 [ocfs2]
    do_vfs_ioctl+0x155/0x510
    SyS_ioctl+0x81/0xa0
    system_call_fastpath+0x18/0xd8
  Code: 18 48 c7 c6 60 7f 65 a0 31 c0 bb e2 ff ff ff 48 8b 4a 40 48 8b 7a 28 48 c7 c2 78 2d 66 a0 e8 38 4f 05 00 e9 28 fe ff ff 0f 1f 00 <0f> 0b 66 0f 1f 44 00 00 bb 86 ff ff ff e9 13 fe ff ff 66 0f 1f
  RIP  ocfs2_get_clusters_nocache.isra.11+0x390/0x550 [ocfs2]
  ---[ end trace c8aa0c8180e869dc ]---
  Kernel panic - not syncing: Fatal exception
  Kernel Offset: disabled

This issue can be reproduced every week in a production environment.

This issue is related to the usage mode.  If others use ocfs2 in this
mode, the kernel will panic frequently.

[akpm@linux-foundation.org: coding style fixes]
[Fix new warning due to unused function by removing said function - Linus ]
Link: http://lkml.kernel.org/r/1568772175-2906-2-git-send-email-sunny.s.zhang@oracle.com
Signed-off-by: Shuning Zhang <sunny.s.zhang@oracle.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Gang He <ghe@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 90 insertions, 44 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 53939bf9d7d2..9876db52913a 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2098,53 +2098,89 @@ static int ocfs2_is_io_unaligned(struct inode *inode, size_t count, loff_t pos)
         return 0;
 }
 
-static int ocfs2_prepare_inode_for_refcount(struct inode *inode,
-                                            struct file *file,
-                                            loff_t pos, size_t count,
-                                            int *meta_level)
+static int ocfs2_inode_lock_for_extent_tree(struct inode *inode,
+                                            struct buffer_head **di_bh,
+                                            int meta_level,
+                                            int overwrite_io,
+                                            int write_sem,
+                                            int wait)
 {
-        int ret;
-        struct buffer_head *di_bh = NULL;
-        u32 cpos = pos >> OCFS2_SB(inode->i_sb)->s_clustersize_bits;
-        u32 clusters =
-                ocfs2_clusters_for_bytes(inode->i_sb, pos + count) - cpos;
+        int ret = 0;
 
-        ret = ocfs2_inode_lock(inode, &di_bh, 1);
-        if (ret) {
-                mlog_errno(ret);
+        if (wait)
+                ret = ocfs2_inode_lock(inode, NULL, meta_level);
+        else
+                ret = ocfs2_try_inode_lock(inode,
+                        overwrite_io ? NULL : di_bh, meta_level);
+        if (ret < 0)
                 goto out;
+
+        if (wait) {
+                if (write_sem)
+                        down_write(&OCFS2_I(inode)->ip_alloc_sem);
+                else
+                        down_read(&OCFS2_I(inode)->ip_alloc_sem);
+        } else {
+                if (write_sem)
+                        ret = down_write_trylock(&OCFS2_I(inode)->ip_alloc_sem);
+                else
+                        ret = down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem);
+
+                if (!ret) {
+                        ret = -EAGAIN;
+                        goto out_unlock;
+                }
         }
 
-        *meta_level = 1;
+        return ret;
 
-        ret = ocfs2_refcount_cow(inode, di_bh, cpos, clusters, UINT_MAX);
-        if (ret)
-                mlog_errno(ret);
+out_unlock:
+        brelse(*di_bh);
+        ocfs2_inode_unlock(inode, meta_level);
 out:
-        brelse(di_bh);
         return ret;
 }
 
+static void ocfs2_inode_unlock_for_extent_tree(struct inode *inode,
+                                               struct buffer_head **di_bh,
+                                               int meta_level,
+                                               int write_sem)
+{
+        if (write_sem)
+                up_write(&OCFS2_I(inode)->ip_alloc_sem);
+        else
+                up_read(&OCFS2_I(inode)->ip_alloc_sem);
+
+        brelse(*di_bh);
+        *di_bh = NULL;
+
+        if (meta_level >= 0)
+                ocfs2_inode_unlock(inode, meta_level);
+}
+
 static int ocfs2_prepare_inode_for_write(struct file *file,
                                          loff_t pos, size_t count, int wait)
 {
         int ret = 0, meta_level = 0, overwrite_io = 0;
+        int write_sem = 0;
         struct dentry *dentry = file->f_path.dentry;
         struct inode *inode = d_inode(dentry);
         struct buffer_head *di_bh = NULL;
+        u32 cpos;
+        u32 clusters;
 
         /*
          * We start with a read level meta lock and only jump to an ex
          * if we need to make modifications here.
          */
         for(;;) {
-                if (wait)
-                        ret = ocfs2_inode_lock(inode, NULL, meta_level);
-                else
-                        ret = ocfs2_try_inode_lock(inode,
-                                overwrite_io ? NULL : &di_bh, meta_level);
+                ret = ocfs2_inode_lock_for_extent_tree(inode,
+                                                       &di_bh,
+                                                       meta_level,
+                                                       overwrite_io,
+                                                       write_sem,
+                                                       wait);
                 if (ret < 0) {
-                        meta_level = -1;
                         if (ret != -EAGAIN)
                                 mlog_errno(ret);
                         goto out;
@@ -2156,15 +2192,8 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
                  */
                 if (!wait && !overwrite_io) {
                         overwrite_io = 1;
-                        if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) {
-                                ret = -EAGAIN;
-                                goto out_unlock;
-                        }
 
                         ret = ocfs2_overwrite_io(inode, di_bh, pos, count);
-                        brelse(di_bh);
-                        di_bh = NULL;
-                        up_read(&OCFS2_I(inode)->ip_alloc_sem);
                         if (ret < 0) {
                                 if (ret != -EAGAIN)
                                         mlog_errno(ret);
@@ -2183,7 +2212,10 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
                  * set inode->i_size at the end of a write. */
                 if (should_remove_suid(dentry)) {
                         if (meta_level == 0) {
-                                ocfs2_inode_unlock(inode, meta_level);
+                                ocfs2_inode_unlock_for_extent_tree(inode,
+                                                                   &di_bh,
+                                                                   meta_level,
+                                                                   write_sem);
                                 meta_level = 1;
                                 continue;
                         }
@@ -2197,18 +2229,32 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
 
                 ret = ocfs2_check_range_for_refcount(inode, pos, count);
                 if (ret == 1) {
-                        ocfs2_inode_unlock(inode, meta_level);
-                        meta_level = -1;
-
-                        ret = ocfs2_prepare_inode_for_refcount(inode,
-                                                               file,
-                                                               pos,
-                                                               count,
-                                                               &meta_level);
+                        ocfs2_inode_unlock_for_extent_tree(inode,
+                                                           &di_bh,
+                                                           meta_level,
+                                                           write_sem);
+                        ret = ocfs2_inode_lock_for_extent_tree(inode,
+                                                               &di_bh,
+                                                               meta_level,
+                                                               overwrite_io,
+                                                               1,
+                                                               wait);
+                        write_sem = 1;
+                        if (ret < 0) {
+                                if (ret != -EAGAIN)
+                                        mlog_errno(ret);
+                                goto out;
+                        }
+
+                        cpos = pos >> OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+                        clusters =
+                                ocfs2_clusters_for_bytes(inode->i_sb, pos + count) - cpos;
+                        ret = ocfs2_refcount_cow(inode, di_bh, cpos, clusters, UINT_MAX);
                 }
 
                 if (ret < 0) {
-                        mlog_errno(ret);
+                        if (ret != -EAGAIN)
+                                mlog_errno(ret);
                         goto out_unlock;
                 }
 
@@ -2219,10 +2265,10 @@ out_unlock:
         trace_ocfs2_prepare_inode_for_write(OCFS2_I(inode)->ip_blkno,
                                             pos, count, wait);
 
-        brelse(di_bh);
-
-        if (meta_level >= 0)
-                ocfs2_inode_unlock(inode, meta_level);
+        ocfs2_inode_unlock_for_extent_tree(inode,
+                                           &di_bh,
+                                           meta_level,
+                                           write_sem);
 
 out:
         return ret;