From: Aneesh Kumar K.V Date: Tue, 17 Feb 2009 15:58:34 +0000 (-0500) Subject: ext4: Fix the race between read_inode_bitmap() and ext4_new_inode() X-Git-Tag: v2.6.27.19~11 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=783a21ed8a1cc3c64484438c20bbed0f1cca2682;p=pandora-kernel.git ext4: Fix the race between read_inode_bitmap() and ext4_new_inode() (cherry picked from commit 393418676a7602e1d7d3f6e560159c65c8cbd50e) We need to make sure we update the inode bitmap and clear EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held, since ext4_read_inode_bitmap() looks at EXT4_BG_INODE_UNINIT to decide whether to initialize the inode bitmap each time it is called. (introduced by commit c806e68f.) ext4_read_inode_bitmap does: spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group)); if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { ext4_init_inode_bitmap(sb, bh, block_group, desc); and ext4_new_inode does if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group), ino, inode_bitmap_bh->b_data)) ...... ... spin_lock(sb_bgl_lock(sbi, group)); gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT); i.e., on allocation we update the bitmap then we take the sb_bgl_lock and clear the EXT4_BG_INODE_UNINIT flag. What can happen is a parallel ext4_read_inode_bitmap can zero out the bitmap in between the above ext4_set_bit_atomic and spin_lock(sb_bg_lock..) The race results in below user visible errors EXT4-fs error (device sdb1): ext4_free_inode: bit already cleared for inode 168449 EXT4-fs warning (device sdb1): ext4_unlink: Deleting nonexistent file ... EXT4-fs warning (device sdb1): ext4_rmdir: empty directory has too many links ... ls: /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71: Stale NFS file handle Signed-off-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" Signed-off-by: Greg Kroah-Hartman --- Reading git-diff-tree failed