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author | npiggin@suse.de <npiggin@suse.de> | 2010-05-27 01:05:33 +1000 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2010-05-27 22:15:33 -0400 |
commit | 7bb46a6734a7e1ad4beaecc11cae7ed3ff81d30f (patch) | |
tree | e575d9c55e2a6ccc645dcb3ae2564de458b428f2 /mm | |
parent | 7000d3c424e5bb350e502a477fb0e1ed42f8b10e (diff) | |
download | kernel_samsung_smdk4412-7bb46a6734a7e1ad4beaecc11cae7ed3ff81d30f.tar.gz kernel_samsung_smdk4412-7bb46a6734a7e1ad4beaecc11cae7ed3ff81d30f.tar.bz2 kernel_samsung_smdk4412-7bb46a6734a7e1ad4beaecc11cae7ed3ff81d30f.zip |
fs: introduce new truncate sequence
Introduce a new truncate calling sequence into fs/mm subsystems. Rather than
setattr > vmtruncate > truncate, have filesystems call their truncate sequence
from ->setattr if filesystem specific operations are required. vmtruncate is
deprecated, and truncate_pagecache and inode_newsize_ok helpers introduced
previously should be used.
simple_setattr is introduced for simple in-ram filesystems to implement
the new truncate sequence. Eventually all filesystems should be converted
to implement a setattr, and the default code in notify_change should go
away.
simple_setsize is also introduced to perform just the ATTR_SIZE portion
of simple_setattr (ie. changing i_size and trimming pagecache).
To implement the new truncate sequence:
- filesystem specific manipulations (eg freeing blocks) must be done in
the setattr method rather than ->truncate.
- vmtruncate can not be used by core code to trim blocks past i_size in
the event of write failure after allocation, so this must be performed
in the fs code.
- convert usage of helpers block_write_begin, nobh_write_begin,
cont_write_begin, and *blockdev_direct_IO* to use _newtrunc postfixed
variants. These avoid calling vmtruncate to trim blocks (see previous).
- inode_setattr should not be used. generic_setattr is a new function
to be used to copy simple attributes into the generic inode.
- make use of the better opportunity to handle errors with the new sequence.
Big problem with the previous calling sequence: the filesystem is not called
until i_size has already changed. This means it is not allowed to fail the
call, and also it does not know what the previous i_size was. Also, generic
code calling vmtruncate to truncate allocated blocks in case of error had
no good way to return a meaningful error (or, for example, atomically handle
block deallocation).
Cc: Christoph Hellwig <hch@lst.de>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/truncate.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/mm/truncate.c b/mm/truncate.c index f42675a3615..937571b8b23 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -548,18 +548,18 @@ EXPORT_SYMBOL(truncate_pagecache); * NOTE! We have to be ready to update the memory sharing * between the file and the memory map for a potential last * incomplete page. Ugly, but necessary. + * + * This function is deprecated and simple_setsize or truncate_pagecache + * should be used instead. */ int vmtruncate(struct inode *inode, loff_t offset) { - loff_t oldsize; int error; - error = inode_newsize_ok(inode, offset); + error = simple_setsize(inode, offset); if (error) return error; - oldsize = inode->i_size; - i_size_write(inode, offset); - truncate_pagecache(inode, oldsize, offset); + if (inode->i_op->truncate) inode->i_op->truncate(inode); |