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46e294efc3
Xattr code using inodes with large xattr data can end up dropping last
inode reference (and thus deleting the inode) from places like
ext4_xattr_set_entry(). That function is called with transaction started
and so ext4_evict_inode() can deadlock against fs freezing like:
CPU1 CPU2
removexattr() freeze_super()
vfs_removexattr()
ext4_xattr_set()
handle = ext4_journal_start()
...
ext4_xattr_set_entry()
iput(old_ea_inode)
ext4_evict_inode(old_ea_inode)
sb->s_writers.frozen = SB_FREEZE_FS;
sb_wait_write(sb, SB_FREEZE_FS);
ext4_freeze()
jbd2_journal_lock_updates()
-> blocks waiting for all
handles to stop
sb_start_intwrite()
-> blocks as sb is already in SB_FREEZE_FS state
Generally it is advisable to delete inodes from a separate transaction
as it can consume quite some credits however in this case it would be
quite clumsy and furthermore the credits for inode deletion are quite
limited and already accounted for. So just tweak ext4_evict_inode() to
avoid freeze protection if we have transaction already started and thus
it is not really needed anyway.
Cc: stable@vger.kernel.org
Fixes: dec214d00e ("ext4: xattr inode deduplication")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127110649.24730-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.