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In f2fs_lookup_extent_tree, et->cached_en was read and updated with only
read lock held,
it could cause __lookup_extent_tree within return entirely wrong
extent_node, if other
thread update et->cached_en just before __lookup_extent_tree return.
However, there are two things about this patch that need to be noticed:
1. It does no good to arrange the order of concurrent read/write, the result
would still
be random in such case.
2. It's built on this assumption: the mix up of reads and writes on a single
pointer would
not make the pointer partially wrong at any time. Please let me know if I'm
wrong, thx.
Signed-off-by: Fan li <fanofcode.li@samsung.com>
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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Add a lookup and a insertion interface for extent tree.
The new lookup return the insert position and the prev/next
extents closest to the offset we lookup when find no match.
The new insertion uses above parameters to improve performance.
There are three possible insertions after the lookup in
f2fs_update_extent_tree, two of them insert parts of removed extent
back to tree, since no merge happens during this process, new insertion
skips the merge check in this scanario; the another insertion inserts a
new extent to tree, new insertion uses prev/next extent and insert
position to insert this extent directly, and save the time of searching
down the tree.
As long as tree remains unchanged between lookup and insertion, this
would work fine. And the new lookup would be useful when add
multi-blocks extent support for insertion interface.
Signed-off-by: Fan li <fanofcode.li@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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Variables for recording extent cache ratio info were updated without
protection, this patch tries to alter them to atomic_t type for more
accurate stat.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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This patch moves extent cache related code from data.c into extent_cache.c
since extent cache is independent feature, and its codes are not relate to
others in data.c, it's better for us to maintain them in separated place.
There is no functionality change, but several small coding style fixes
including:
* rename __drop_largest_extent to f2fs_drop_largest_extent for exporting;
* rename misspelled word 'untill' to 'until';
* remove unneeded 'return' in the end of f2fs_destroy_extent_tree().
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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