vfs: Add no_nrwrite_index_update writeback control flag
If no_nrwrite_index_update is set we don't update nr_to_write and address space writeback_index in write_cache_pages. This change enables a file system to skip these updates in write_cache_pages and do them in the writepages() callback. This patch will be followed by an ext4 patch that make use of these new flags. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> CC: linux-fsdevel@vger.kernel.org
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@ -63,6 +63,15 @@ struct writeback_control {
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unsigned for_writepages:1; /* This is a writepages() call */
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unsigned range_cyclic:1; /* range_start is cyclic */
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unsigned more_io:1; /* more io to be dispatched */
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/*
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* write_cache_pages() won't update wbc->nr_to_write and
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* mapping->writeback_index if no_nrwrite_index_update
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* is set. write_cache_pages() may write more than we
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* requested and we want to make sure nr_to_write and
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* writeback_index are updated in a consistent manner
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* so we use a single control to update them
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*/
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unsigned no_nrwrite_index_update:1;
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};
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/*
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@ -876,6 +876,7 @@ int write_cache_pages(struct address_space *mapping,
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pgoff_t end; /* Inclusive */
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int scanned = 0;
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int range_whole = 0;
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long nr_to_write = wbc->nr_to_write;
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if (wbc->nonblocking && bdi_write_congested(bdi)) {
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wbc->encountered_congestion = 1;
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@ -939,7 +940,7 @@ retry:
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unlock_page(page);
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ret = 0;
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}
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if (ret || (--(wbc->nr_to_write) <= 0))
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if (ret || (--nr_to_write <= 0))
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done = 1;
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if (wbc->nonblocking && bdi_write_congested(bdi)) {
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wbc->encountered_congestion = 1;
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@ -958,8 +959,11 @@ retry:
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index = 0;
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goto retry;
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}
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if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
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mapping->writeback_index = index;
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if (!wbc->no_nrwrite_index_update) {
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if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
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mapping->writeback_index = index;
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wbc->nr_to_write = nr_to_write;
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}
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return ret;
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}
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