linux-toradex.git/fs/ext4/ext4_jbd2.h, branch v4.10

ext4: do not perform data journaling when data is encrypted

2016-12-10T22:54:58+00:00

Currently data journalling is incompatible with encryption: enabling both
at the same time has never been supported by design, and would result in
unpredictable behavior. However, users are not precluded from turning on
both features simultaneously. This change programmatically replaces data
journaling for encrypted regular files with ordered data journaling mode.

Background:
Journaling encrypted data has not been supported because it operates on
buffer heads of the page in the page cache. Namely, when the commit
happens, which could be up to five seconds after caching, the commit
thread uses the buffer heads attached to the page to copy the contents of
the page to the journal. With encryption, it would have been required to
keep the bounce buffer with ciphertext for up to the aforementioned five
seconds, since the page cache can only hold plaintext and could not be
used for journaling. Alternatively, it would be required to setup the
journal to initiate a callback at the commit time to perform deferred
encryption - in this case, not only would the data have to be written
twice, but it would also have to be encrypted twice. This level of
complexity was not justified for a mode that in practice is very rarely
used because of the overhead from the data journalling.

Solution:
If data=journaled has been set as a mount option for a filesystem, or if
journaling is enabled on a regular file, do not perform journaling if the
file is also encrypted, instead fall back to the data=ordered mode for the
file.

Rationale:
The intent is to allow seamless and proper filesystem operation when
journaling and encryption have both been enabled, and have these two
conflicting features gracefully resolved by the filesystem.

Fixes: 4461471107b7
Signed-off-by: Sergey Karamov 
Signed-off-by: Theodore Ts'o 
Cc: stable@vger.kernel.org

ext4: optimize ext4_should_retry_alloc() to improve ENOSPC performance

2016-06-26T22:24:01+00:00

If there are no pending blocks to be released after a commit, forcing
a journal commit has no hope of helping.  It's possible that a commit
had just completed, so if there are now free blocks available for
allocation, it's worth retrying the commit.

Reported-by: Chao Yu 
Signed-off-by: Theodore Ts'o

ext4: do not ask jbd2 to write data for delalloc buffers

2016-04-24T04:56:08+00:00

Currently we ask jbd2 to write all dirty allocated buffers before
committing a transaction when doing writeback of delay allocated blocks.
However this is unnecessary since we move all pages to writeback state
before dropping a transaction handle and then submit all the necessary
IO. We still need the transaction commit to wait for all the outstanding
writeback before flushing disk caches during transaction commit to avoid
data exposure issues though. Use the new jbd2 capability and ask it to
only wait for outstanding writeback during transaction commit when
writing back data in ext4_writepages().

Tested-by: "HUANG Weller (CM/ESW12-CN)" 
Signed-off-by: Jan Kara 
Signed-off-by: Theodore Ts'o

jbd2: add support for avoiding data writes during transaction commits

2016-04-24T04:56:07+00:00

Currently when filesystem needs to make sure data is on permanent
storage before committing a transaction it adds inode to transaction's
inode list. During transaction commit, jbd2 writes back all dirty
buffers that have allocated underlying blocks and waits for the IO to
finish. However when doing writeback for delayed allocated data, we
allocate blocks and immediately submit the data. Thus asking jbd2 to
write dirty pages just unnecessarily adds more work to jbd2 possibly
writing back other redirtied blocks.

Add support to jbd2 to allow filesystem to ask jbd2 to only wait for
outstanding data writes before committing a transaction and thus avoid
unnecessary writes.

Signed-off-by: Jan Kara 
Signed-off-by: Theodore Ts'o

ext4: clean up feature test macros with predicate functions

2015-10-17T20:18:43+00:00

Create separate predicate functions to test/set/clear feature flags,
thereby replacing the wordy old macros.  Furthermore, clean out the
places where we open-coded feature tests.

Signed-off-by: Darrick J. Wong

ext4: don't use MAXQUOTAS value

2014-09-11T15:15:15+00:00

MAXQUOTAS value defines maximum number of quota types VFS supports.
This isn't necessarily the number of types ext4 supports. Although
ext4 will support project quotas, use ext4 private definition for
consistency with other filesystems.

Signed-off-by: Jan Kara 
Signed-off-by: Theodore Ts'o

ext4: make local functions static

2014-05-12T14:50:23+00:00

I have been running make namespacecheck to look for unneeded globals, and
found these in ext4.

Signed-off-by: Stephen Hemminger 
Signed-off-by: "Theodore Ts'o"

ext4: Fix misspellings using 'codespell' tool

2013-08-28T18:40:12+00:00

Signed-off-by: Anatol Pomozov 
Signed-off-by: "Theodore Ts'o"

ext4: use transaction reservation for extent conversion in ext4_end_io

2013-06-04T17:21:11+00:00

Later we would like to clear PageWriteback bit only after extent
conversion from unwritten to written extents is performed.  However it
is not possible to start a transaction after PageWriteback is set
because that violates lock ordering (and is easy to deadlock).  So we
have to reserve a transaction before locking pages and sending them
for IO and later we use the transaction for extent conversion from
ext4_end_io().

Reviewed-by: Zheng Liu 
Signed-off-by: Jan Kara 
Signed-off-by: "Theodore Ts'o"

ext4: provide wrappers for transaction reservation calls

2013-06-04T16:37:50+00:00

Reviewed-by: Zheng Liu 
Signed-off-by: Jan Kara 
Signed-off-by: "Theodore Ts'o"