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From 3176671662bda79d4b4059b8cc22b4b31a6547e0 Mon Sep 17 00:00:00 2001
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From: Maurizio Lombardi <mlombard@redhat.com>
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Date: Fri, 13 Nov 2020 11:44:40 +0100
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Subject: [PATCH] fileio backstore: fix sparse file creation
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fallocate() can't be used to create sparse files because it
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actually preallocates all the disk space that will be used by the file
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backstore, sparse files do not have preallocated disk space
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by definition.
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We must therefore use ftruncate().
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We can, on the other hand, use fallocate() to create non-sparse
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files and fall back to the slower "while() fwrite()" if we
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are running on Python version < 3.3 where fallocate() is not available
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Fixes 3bd4d8ef7c9b154c53e8b8dd863a570bce7f5c2c
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Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
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---
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targetcli/ui_backstore.py | 16 ++++++++--------
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1 file changed, 8 insertions(+), 8 deletions(-)
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diff --git a/targetcli/ui_backstore.py b/targetcli/ui_backstore.py
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index 8692f22..9bc0c58 100644
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--- a/targetcli/ui_backstore.py
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+++ b/targetcli/ui_backstore.py
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@@ -423,17 +423,17 @@ class UIFileIOBackstore(UIBackstore):
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raise ExecutionError("Could not open %s" % filename)
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try:
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if sparse:
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+ os.ftruncate(f.fileno(), size)
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+ else:
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+ self.shell.log.info("Writing %d bytes" % size)
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try:
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+ # Prior to version 3.3, Python does not provide fallocate
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os.posix_fallocate(f.fileno(), 0, size)
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except AttributeError:
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- # Prior to version 3.3, Python does not provide fallocate
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- os.ftruncate(f.fileno(), size)
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- else:
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- self.shell.log.info("Writing %d bytes" % size)
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- while size > 0:
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- write_size = min(size, 1024)
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- f.write("\0" * write_size)
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- size -= write_size
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+ while size > 0:
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+ write_size = min(size, 1024)
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+ f.write("\0" * write_size)
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+ size -= write_size
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except (OSError, IOError):
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os.remove(filename)
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raise ExecutionError("Could not expand file to %d bytes" % size)
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--
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2.28.0
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