Recently merged shared-sb capability causes kernel to crash when we try to do mounts and umounts simultaneously on the same machine. The patch fixes umount codepath by doing kill_anon_super at first (it calls generic_shutdown_super that tries to take sb_lock and removes a superblock from fs_supers list) and then processing cifs_umount (that frees cifs related fields).
In this case when we call sget and it calls cifs_match_super under sb_lock for every entry from fs_supers list, we can be sure that all cifs related fields are not freed by simultaneous umount. Signed-off-by: Pavel Shilovsky <[email protected]> --- fs/cifs/cifsfs.c | 19 ++++++++++++++++--- 1 files changed, 16 insertions(+), 3 deletions(-) diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 989442d..3537e7d 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -180,16 +180,30 @@ out_mount_failed: static void cifs_put_super(struct super_block *sb) { + struct cifs_sb_info *cifs_sb = CIFS_SB(sb); + if (cifs_sb == NULL) { + cFYI(1, "Empty cifs superblock info passed to put_super"); + return; + } + + bdi_destroy(&cifs_sb->bdi); +} + +static void +cifs_kill_super(struct super_block *sb) +{ int rc = 0; struct cifs_sb_info *cifs_sb; cFYI(1, "In cifs_put_super"); cifs_sb = CIFS_SB(sb); if (cifs_sb == NULL) { - cFYI(1, "Empty cifs superblock info passed to unmount"); + cFYI(1, "Empty cifs superblock info passed to kill_super"); return; } + kill_anon_super(sb); + rc = cifs_umount(sb, cifs_sb); if (rc) cERROR(1, "cifs_umount failed with return code %d", rc); @@ -199,7 +213,6 @@ cifs_put_super(struct super_block *sb) } unload_nls(cifs_sb->local_nls); - bdi_destroy(&cifs_sb->bdi); kfree(cifs_sb); } @@ -807,7 +820,7 @@ struct file_system_type cifs_fs_type = { .owner = THIS_MODULE, .name = "cifs", .mount = cifs_do_mount, - .kill_sb = kill_anon_super, + .kill_sb = cifs_kill_super, /* .fs_flags */ }; const struct inode_operations cifs_dir_inode_ops = { -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
