fat (exportfs): rebuild inode if ilookup() fails

If the cache lookups fail,use the i_pos value to find the directory entry
of the inode and rebuild the inode.Since this involves accessing the FAT
media, do this only if the nostale_ro nfs mount option is specified.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ravishankar N <ravi.n1@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 52 insertions, 5 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index c517fc066cf7..413eaaf30ed5 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -75,6 +75,7 @@ struct msdos_sb_info {
         unsigned long root_cluster;   /* first cluster of the root directory */
         unsigned long fsinfo_sector;  /* sector number of FAT32 fsinfo */
         struct mutex fat_lock;
+        struct mutex nfs_build_inode_lock;
         struct mutex s_lock;
         unsigned int prev_free;      /* previously allocated cluster number */
         unsigned int free_clusters;  /* -1 if undefined */
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 27f49f4fa0d3..971ba7d549da 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -443,12 +443,25 @@ static int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
         return 0;
 }
 
+static inline void fat_lock_build_inode(struct msdos_sb_info *sbi)
+{
+        if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+                mutex_lock(&sbi->nfs_build_inode_lock);
+}
+
+static inline void fat_unlock_build_inode(struct msdos_sb_info *sbi)
+{
+        if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+                mutex_unlock(&sbi->nfs_build_inode_lock);
+}
+
 struct inode *fat_build_inode(struct super_block *sb,
                         struct msdos_dir_entry *de, loff_t i_pos)
 {
         struct inode *inode;
         int err;
 
+        fat_lock_build_inode(MSDOS_SB(sb));
         inode = fat_iget(sb, i_pos);
         if (inode)
                 goto out;
@@ -468,6 +481,7 @@ struct inode *fat_build_inode(struct super_block *sb,
         fat_attach(inode, i_pos);
         insert_inode_hash(inode);
 out:
+        fat_unlock_build_inode(MSDOS_SB(sb));
         return inode;
 }
 
@@ -1247,6 +1261,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
         sb->s_magic = MSDOS_SUPER_MAGIC;
         sb->s_op = &fat_sops;
         sb->s_export_op = &fat_export_ops;
+        mutex_init(&sbi->nfs_build_inode_lock);
         ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,
                              DEFAULT_RATELIMIT_BURST);
 
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
index d59c02543a10..0748196889b2 100644
--- a/fs/fat/nfs.c
+++ b/fs/fat/nfs.c
@@ -50,19 +50,50 @@ static struct inode *fat_dget(struct super_block *sb, int i_logstart)
         return inode;
 }
 
+static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
+{
+        if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
+                return fat_iget(sb, i_pos);
+
+        else {
+                if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
+                        return NULL;
+                return ilookup(sb, ino);
+        }
+}
+
 static struct inode *__fat_nfs_get_inode(struct super_block *sb,
                                        u64 ino, u32 generation, loff_t i_pos)
 {
-        struct inode *inode;
-
-        if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
-                return NULL;
+        struct inode *inode = fat_ilookup(sb, ino, i_pos);
 
-        inode = ilookup(sb, ino);
         if (inode && generation && (inode->i_generation != generation)) {
                 iput(inode);
                 inode = NULL;
         }
+        if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
+                struct buffer_head *bh = NULL;
+                struct msdos_dir_entry *de ;
+                sector_t blocknr;
+                int offset;
+                fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
+                bh = sb_bread(sb, blocknr);
+                if (!bh) {
+                        fat_msg(sb, KERN_ERR,
+                                "unable to read block(%llu) for building NFS inode",
+                                (llu)blocknr);
+                        return inode;
+                }
+                de = (struct msdos_dir_entry *)bh->b_data;
+                /* If a file is deleted on server and client is not updated
+                 * yet, we must not build the inode upon a lookup call.
+                 */
+                if (IS_FREE(de[offset].name))
+                        inode = NULL;
+                else
+                        inode = fat_build_inode(sb, &de[offset], i_pos);
+                brelse(bh);
+        }
 
         return inode;
 }