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e22834f024
ext4lazyinit is a global thread. This thread performs itable
initalization under li_list_mtx mutex.
It basically does the following:
ext4_lazyinit_thread
->mutex_lock(&eli->li_list_mtx);
->ext4_run_li_request(elr)
->ext4_init_inode_table-> Do a lot of IO if the list is large
And when new mount/umount arrive they have to block on ->li_list_mtx
because lazy_thread holds it during full walk procedure.
ext4_fill_super
->ext4_register_li_request
->mutex_lock(&ext4_li_info->li_list_mtx);
->list_add(&elr->lr_request, &ext4_li_info >li_request_list);
In my case mount takes 40minutes on server with 36 * 4Tb HDD.
Common user may face this in case of very slow dev ( /dev/mmcblkXXX)
Even more. If one of filesystems was frozen lazyinit_thread will simply
block on sb_start_write() so other mount/umount will be stuck forever.
This patch changes logic like follows:
- grab ->s_umount read sem before processing new li_request.
After that it is safe to drop li_list_mtx because all callers of
li_remove_request are holding ->s_umount for write.
- li_thread skips frozen SB's
Locking order:
Mh KOrder is asserted by umount path like follows: s_umount ->li_list_mtx so
the only way to to grab ->s_mount inside li_thread is via down_read_trylock
xfstests:ext4/023
#PSBM-49658
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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| .. | ||
| acl.c | ||
| acl.h | ||
| balloc.c | ||
| bitmap.c | ||
| block_validity.c | ||
| dir.c | ||
| ext4_extents.h | ||
| ext4_jbd2.c | ||
| ext4_jbd2.h | ||
| ext4.h | ||
| extents_status.c | ||
| extents_status.h | ||
| extents.c | ||
| file.c | ||
| fsync.c | ||
| hash.c | ||
| ialloc.c | ||
| indirect.c | ||
| inline.c | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| Makefile | ||
| mballoc.c | ||
| mballoc.h | ||
| migrate.c | ||
| mmp.c | ||
| move_extent.c | ||
| namei.c | ||
| page-io.c | ||
| readpage.c | ||
| resize.c | ||
| super.c | ||
| symlink.c | ||
| sysfs.c | ||
| truncate.h | ||
| xattr_security.c | ||
| xattr_trusted.c | ||
| xattr_user.c | ||
| xattr.c | ||
| xattr.h | ||